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135-450: Ventricular tachycardia can occur due to coronary heart disease , aortic stenosis , cardiomyopathy , electrolyte imbalance , or a heart attack . Diagnosis is by an electrocardiogram (ECG) showing a rate of greater than 120 beats per minute and at least three wide QRS complexes in a row. It is classified as non-sustained versus sustained based on whether it lasts less than or more than 30 seconds. The term ventricular arrhythmia refers to

270-417: A coronary care unit for possible complications (such as cardiac arrhythmias – irregularities in the heart rate). Depending on the risk assessment, stress testing or angiography may be used to identify and treat coronary artery disease in patients who have had an NSTEMI or unstable angina. There are various risk assessment systems for determining the risk of coronary artery disease, with various emphasis on

405-435: A corrected QT interval of greater than 450–500 milliseconds is found, but clinical findings, other EKG features, and genetic testing may confirm the diagnosis with shorter QT intervals. Management may include avoiding strenuous exercise, getting sufficient potassium in the diet, the use of beta blockers , or an implantable cardiac defibrillator . For people with LQTS who survive cardiac arrest and remain untreated,

540-619: A healthy diet , regularly exercising , maintaining a healthy weight, and not smoking. Medications for diabetes, high cholesterol, or high blood pressure are sometimes used. There is limited evidence for screening people who are at low risk and do not have symptoms. Treatment involves the same measures as prevention. Additional medications such as antiplatelets (including aspirin ), beta blockers , or nitroglycerin may be recommended. Procedures such as percutaneous coronary intervention (PCI) or coronary artery bypass surgery (CABG) may be used in severe disease. In those with stable CAD it

675-467: A myocardial infarction . The morphology of the tachycardia depends on its cause and the origin of the re-entry electrical circuit in the heart. In monomorphic ventricular tachycardia, the shape of each heart beat on the ECG looks the same because the impulse is either being generated from increased automaticity of a single point in either the left or the right ventricle, or due to a reentry circuit within

810-472: A 15% increase in arrhythmic risk. As the QT prolonging effects of both genetic variants and acquired causes of LQTS are additive, those with inherited LQTS are more likely to experience TdP if given QT prolonging drugs or if they experience electrolyte problems such as low blood levels of low potassium ( hypokalaemia ). Similarly, those taking QT prolonging medications are more likely to experience TdP if they have

945-504: A Schwartz score of greater than 3 or if a pathogenic genetic variant associated with LQTS is identified, regardless of QT interval. Those diagnosed with LQTS are usually advised to avoid drugs that can prolong the QT interval further or lower the threshold for TDP, lists of which can be found in public access online databases . In addition to this, two intervention options are known for individuals with LQTS: arrhythmia prevention and arrhythmia termination. Arrhythmia suppression involves

1080-683: A combination of genetic predisposition and environmental factors. Organizations such as the Indian Heart Association are working with the World Heart Federation to raise awareness about this issue. Coronary artery disease is the leading cause of death for both males and females and accounts for approximately 600,000 deaths in the United States every year. According to present trends in the United States, half of healthy 40-year-old males will develop CAD in

1215-415: A complete loop and self-perpetuating. The twisting pattern on the ECG can be explained by movement of the core of the re-entrant circuit in the form of a meandering spiral wave . Diagnosing long QT syndrome is challenging. Whilst the hallmark of LQTS is prolongation of the QT interval, the QT interval is highly variable among both those who are healthy and those who have LQTS. This leads to overlap between

1350-741: A few seconds may not result in problems, longer periods are dangerous. Short periods may occur without symptoms or present with lightheadedness, palpitations , shortness of breath , chest pain , or unconsciousness . Ventricular tachycardia may turn into ventricular fibrillation and can result in cardiac arrest . Ventricular tachycardia can occur due to coronary heart disease , aortic stenosis , cardiomyopathy , electrolyte problems (e.g., low blood levels of magnesium or potassium ), inherited channelopathies (e.g., long-QT syndrome ), catecholaminergic polymorphic ventricular tachycardia , arrhythmogenic right ventricular dysplasia , alcohol withdrawal syndrome (typically following atrial fibrillation ), or

1485-1078: A genetic tendency to a prolonged QT interval, even it this tendency is concealed. Arrhythmias occur more commonly in drug-induced LQTS if the medication in question has been rapidly given intravenously , or if high concentrations of the drug are present in the person's blood. The risk of arrhythmias is also higher if the person receiving the drug has heart failure , is taking digitalis , or has recently been cardioverted from atrial fibrillation . Other risk factors for developing torsades de pointes among those with LQTS include female sex, increasing age, pre-existing cardiovascular disease , and abnormal liver or kidney function . There are several subtypes of long QT syndrome. These can be broadly split into those caused by genetic mutations which those affected are born with, carry throughout their lives, and can pass on to their children (inherited or congenital long QT syndrome), and those caused by other factors which cannot be passed on and are often reversible (acquired long QT syndrome). Inherited, or congenital long QT syndrome,

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1620-405: A given age also decreased between 1990 and 2010. In the United States in 2010, about 20% of those over 65 had CAD, while it was present in 7% of those 45 to 64, and 1.3% of those 18 to 45; rates were higher among males than females of a given age. The most common symptom is chest pain or discomfort that occurs regularly with activity, after eating, or at other predictable times; this phenomenon

1755-490: A heart attack or myocardial infarction, and immediate emergency medical services are crucial. With advanced disease, the narrowing of coronary arteries reduces the supply of oxygen-rich blood flowing to the heart, which becomes more pronounced during strenuous activities during which the heart beats faster and has an increased oxygen demand. For some, this causes severe symptoms, while others experience no symptoms at all. Symptoms in females can differ from those in males, and

1890-443: A history of a myocardial infarction , congestive heart failure , or recent angina , the wide complex tachycardia is much more likely to be ventricular tachycardia. The proper diagnosis is important, as the misdiagnosis of supraventricular tachycardia when ventricular tachycardia is present is associated with worse prognosis. This is particularly true if calcium channel blockers , such as verapamil , are used to attempt to terminate

2025-431: A myocardial infarction but does not change the overall risk of death. Aspirin therapy to prevent heart disease is thus recommended only in adults who are at increased risk for cardiovascular events, which may include postmenopausal females, males above 40, and younger people with risk factors for coronary heart disease, including high blood pressure , a family history of heart disease, or diabetes . The benefits outweigh

2160-420: A net inward current. While there is strong evidence that the trigger for torsades de pointes comes from afterdepolarisations, it is less certain what sustains this arrhythmia. Some lines of evidence suggest that repeated afterdepolarisations from many sources contribute to the continuing arrhythmia. However, some suggest that the arrhythmia sustains through a mechanism known as re-entry. According to this model,

2295-404: A neuropsychological assessment. There are a number of treatment options for coronary artery disease: It is recommended that blood pressure typically be reduced to less than 140/90 mmHg. The diastolic blood pressure however should not be lower than 60 mmHg. Beta-blockers are recommended first line for this use. In those with no previous history of heart disease, aspirin decreases the risk of

2430-402: A normal QT interval at rest (concealed LQTS). Those with the longest QT intervals are more likely to experience TdP, and a corrected QT interval of greater than 500 ms is thought to represent those at higher risk. Despite this, those with only subtle QT prolongation or concealed LQTS still have some risk of arrhythmias. Overall, every 10 ms increase in the corrected QT interval is associated with

2565-473: A person still has a pulse, it is usually possible to terminate the episode using electric cardioversion. This should be synchronized to the heartbeat if the waveform is monomorphic if possible, in order to avoid degeneration of the rhythm to ventricular fibrillation . An initial energy of 100J is recommended. If the waveform is polymorphic, then higher energies and an unsynchronized shock should be provided (also known as defibrillation). A person with pulseless VT

2700-406: A pre-existing bundle branch block are commonly misdiagnosed as ventricular tachycardia. Other rarer phenomena include Ashman beats and antidromic atrioventricular re-entry tachycardias . Various diagnostic criteria have been developed to determine whether a wide complex tachycardia is ventricular tachycardia or a more benign rhythm. In addition to these diagnostic criteria, if the individual has

2835-410: A presumed supraventricular tachycardia. Therefore, it is wisest to assume that all wide complex tachycardia is VT until proven otherwise. ECG features of Ventricular Tachycardia in addition to the increased Heart rate are: Ventricular tachycardia can be classified based on its morphology : Another way to classify ventricular tachycardias is the duration of the episodes : Three or more beats in

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2970-516: A reduction in the early peak current can cause Brugada syndrome and cardiac conduction disease, while other variants have been associated with dilated cardiomyopathy . Some variants which affect both the early and late sodium current can cause overlap syndromes which combine aspects of both LQT3 and Brugada syndrome. LQT5 is caused by variants in the KCNE1 gene responsible for the potassium channel beta subunit MinK. This subunit, in conjunction with

3105-421: A result of myocardial ischemia. Class III anti-arrhythmic drugs such as sotalol and amiodarone prolong the QT interval and may in some circumstances be pro-arrhythmic. Other relatively common drugs including some antibiotics and antihistamines may also be a danger, in particular in combination with one another. Problems with blood levels of potassium, magnesium and calcium may also contribute. High-dose magnesium

3240-427: A role. The diagnosis of CAD depends largely on the nature of the symptoms and imaging. The first investigation when CAD is suspected is an electrocardiogram (ECG/EKG), both for stable angina and acute coronary syndrome. An X-ray of the chest , blood tests and resting echocardiography may be performed. For stable symptomatic patients, several non-invasive tests can diagnose CAD depending on pre-assessment of

3375-413: A row on an ECG that originate from the ventricle at a rate of more than 120 beats per minute constitute a ventricular tachycardia. A third way to classify ventricular tachycardia is on the basis of its symptoms : Pulseless VT is associated with no effective cardiac output, hence, no effective pulse, and is a cause of cardiac arrest (see also: pulseless electrical activity [PEA]). In this circumstance, it

3510-558: A safe and feasible procedure that may offer some advantages over conventional CABG though it is more expensive. As of 2010, CAD was the leading cause of death globally resulting in over 7 million deaths. This increased from 5.2 million deaths from CAD worldwide in 1990. It may affect individuals at any age but becomes dramatically more common at progressively older ages, with approximately a tripling with each decade of life. Males are affected more often than females. The World Health Organization reported that: "The world's biggest killer

3645-416: A significant role in stiffening the arteries and inducing the early phase of coronary arteriosclerosis . This can be seen in a so-called metastatic mechanism of calciphylaxis as it occurs in chronic kidney disease and hemodialysis . Although these people have kidney dysfunction, almost fifty percent of them die due to coronary artery disease. Plaques can be thought of as large "pimples" that protrude into

3780-480: A small lower jaw ( micrognathia ), low set ears, and fused or abnormally angled fingers and toes ( syndactyly and clinodactyly ). The condition is inherited in an autosomal-dominant manner and is caused by mutations in the KCNJ2 gene which encodes the potassium channel protein K ir 2.1. LQT8, also known as Timothy syndrome combines a prolonged QT interval with fused fingers or toes (syndactyly). Abnormalities of

3915-403: Is Jervell and Lange-Nielsen syndrome, an autosomal recessive form of LQTS combining a prolonged QT interval with congenital deafness. Other rare forms include Andersen–Tawil syndrome (LQT7) with features including a prolonged QT interval, periodic paralysis, and abnormalities of the face and skeleton; and Timothy syndrome (LQT8) in which a prolonged QT interval is associated with abnormalities in

4050-829: Is a potentially definitive treatment option for those with recurrent VT. Remote magnetic navigation is one effective method to do the procedure. In the past, ablation was often not considered until pharmacological options had been exhausted, often after the patient had developed substantial morbidity from recurrent episodes of VT and ICD shocks. Antiarrhythmic medications can reduce the frequency of ICD therapies, but have efficacy varies and side effects can be significant. Advances in technology and understanding of VT substrates now allow ablation of multiple and unstable VTs with acceptable safety and efficacy, even in patients with advanced heart disease. Coronary heart disease Coronary artery disease ( CAD ), also called coronary heart disease ( CHD ), or ischemic heart disease ( IHD ),

4185-516: Is a rare form of LQTS inherited in an autosomal recessive manner. In addition to severe prolongation of the QT interval, those affected are born with severe sensorineural deafness affecting both ears. The syndrome is caused by inheriting two copies of certain variant in the KCNE1 or KCNQ1 genes. The same genetic variants lead to the LQT5 and LQT1 forms of Romano-Ward syndrome if only a single copy of

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4320-417: Is a type of heart disease involving the reduction of blood flow to the cardiac muscle due to a build-up of atheromatous plaque in the arteries of the heart . It is the most common of the cardiovascular diseases . CAD can cause stable angina , unstable angina , myocardial ischemia, and myocardial infarction . A common symptom is angina, which is chest pain or discomfort which may travel into

4455-552: Is also associated with certain types of long QT syndrome. The arrhythmias that lead to faints and sudden death are more likely to occur in specific circumstances, in part determined by which genetic variant is present. While arrhythmias can occur at any time, in some forms of LQTS arrhythmias are more commonly seen in response to exercise or mental stress (LQT1), in other forms following a sudden loud noise (LQT2), and in some forms during sleep or immediately upon waking (LQT3). Some rare forms of long QT syndrome affect other parts of

4590-472: Is an auxiliary beta-subunit (Na V β4) forming cardiac sodium channels, variants in which increase the late sustained sodium current. LQT13 is caused by variants in GIRK4, a protein involved in the parasympathetic modulation of the heart. Clinically, the patients are characterized by only modest QT prolongation, but an increased propensity for atrial arrhythmias. LQT14, LQT15 and LQT16 are caused by variants in

4725-570: Is another way of risk assessment. In one study the relative risk of incident coronary events was 91% higher among participants at high genetic risk than among those at low genetic risk. Up to 90% of cardiovascular disease may be preventable if established risk factors are avoided. Prevention involves adequate physical exercise , decreasing obesity , treating high blood pressure , eating a healthy diet , decreasing cholesterol levels, and stopping smoking . Medications and exercise are roughly equally effective. High levels of physical activity reduce

4860-410: Is available. In the absence of ST-segment elevation, heart damage is detected by cardiac markers (blood tests that identify heart muscle damage). If there is evidence of damage ( infarction ), the chest pain is attributed to a "non-ST elevation MI" (NSTEMI). If there is no evidence of damage, the term "unstable angina" is used. This process usually necessitates hospital admission and close observation on

4995-455: Is best treated the same way as ventricular fibrillation (VF), and is recognized as one of the shockable rhythms on the cardiac arrest protocol. Some VT is associated with reasonable cardiac output and may even be asymptomatic. The heart usually tolerates this rhythm poorly in the medium to long term, and patients may certainly deteriorate to pulseless VT or to VF. Occasionally in ventricular tachycardia, supraventricular impulses are conducted to

5130-432: Is better than procainamide. As a low magnesium level in the blood is a common cause of VT, magnesium sulfate can be given for torsades de pointes or if a low blood magnesium level is found/suspected. Long-term anti-arrhythmic therapy may be indicated to prevent recurrence of VT. Beta-blockers and a number of class III anti-arrhythmics are commonly used, such as the beta-blockers carvedilol, metoprolol, and bisoprolol, and

5265-507: Is called a myocardial infarction (commonly referred to as a heart attack). It leads to damage, death, and eventual scarring of the heart muscle without regrowth of heart muscle cells. Chronic high-grade narrowing of the coronary arteries can induce transient ischemia which leads to the induction of a ventricular arrhythmia , which may terminate into a dangerous heart rhythm known as ventricular fibrillation , which often leads to death. Typically, coronary artery disease occurs when part of

5400-400: Is caused by genetic abnormalities. LQTS can arise from variants in several genes, leading in some cases to quite different features. The common thread linking these variants is that they affect one or more ion currents leading to prolongation of the ventricular action potential , thus lengthening the QT interval. Classification systems have been proposed to distinguish between subtypes of

5535-426: Is caused by variants in the calcium channel Cav1.2 encoded by the gene CACNA1c . The following is a list of genes associated with Long QT syndrome: Although long QT syndrome is often a genetic condition, a prolonged QT interval associated with an increased risk of abnormal heart rhythms can also occur in people without a genetic abnormality, commonly due to a side effect of medications. Drug-induced QT prolongation

Ventricular tachycardia - Misplaced Pages Continue

5670-457: Is caused by variants in the membrane structural protein, caveolin -3. Caveolins form specific membrane domains called caveolae in which voltage-gated sodium channels sit. Similar to LQT3, these caveolin variants increase the late sustained sodium current, which impairs cellular repolarization . LQT10 is an extremely rare subtype, caused by variants in the SCN4B gene. The product of this gene

5805-503: Is characterized by heart problems that result from atherosclerosis. Atherosclerosis is a type of arteriosclerosis which is the "chronic inflammation of the arteries which causes them to harden and accumulate cholesterol plaques (atheromatous plaques) on the artery walls". CAD has several well-determined risk factors that contribute to atherosclerosis. These risk factors for CAD include "smoking, diabetes, high blood pressure (hypertension), abnormal (high) amounts of cholesterol and other fat in

5940-415: Is found in cardiac muscle; it is a 'cytolinker' that connects actin and desmin to facilitate cytoskeletal function and vesicular movement. The endocytic pathway is further modulated by changes in tubulin , a key microtubule protein, and fidgetin , a tubulin-severing enzyme that is a marker for cardiovascular risk identified by genome-wide association study . Protein recycling would be modulated by changes in

6075-491: Is inferior to non-invasive imaging methods due to the risk of false negative and false positive test results. The use of non-invasive imaging is not recommended on individuals who are exhibiting no symptoms and are otherwise at low risk for developing coronary disease. Invasive testing with coronary angiography (ICA) can be used when non-invasive testing is inconclusive or show a high event risk. The diagnosis of microvascular angina (previously known as cardiac syndrome X –

6210-459: Is ischemic heart disease, responsible for 13% of the world's total deaths. Since 2000, the largest increase in deaths has been for this disease, rising by 2.7 million to 9.1 million deaths in 2021." It is estimated that 60% of the world's cardiovascular disease burden will occur in the South Asian subcontinent despite only accounting for 20% of the world's population. This may be secondary to

6345-687: Is linked to an increased risk of coronary disease. The consumption of different types of fats including trans fat (trans unsaturated), and saturated fat , in a diet "influences the level of cholesterol that is present in the bloodstream". Unsaturated fats originate from plant sources (such as oils). There are two types of unsaturated fats, cis and trans isomers. Cis unsaturated fats are bent in molecular structure and trans are linear in structure. Saturated fats originate from animal sources (such as animal fats) and are also molecularly linear in structure. The linear configurations of unsaturated trans and saturated fats allow them to easily accumulate and stack at

6480-468: Is more effective than hemoglobin A1c (HbA1c) for detecting dysglycemia in patients with coronary artery disease. The study highlighted that 2-hour post-load glucose levels of at least 9 mmol/L were strong predictors of cardiovascular outcomes, while HbA1c levels of at least 5.9% were also significant but not independently associated when combined with OGTT results. A diet high in fruits and vegetables decreases

6615-489: Is most commonly used to provide rapid relief for acute angina attacks and as a complement to anti-anginal treatments in patients with refractory and recurrent angina. When nitroglycerine enters the bloodstream, it forms free radical nitric oxide, or NO, which activates guanylate cyclase and in turn stimulates the release of cyclic GMP. This molecular signaling stimulates smooth muscle relaxation, ultimately resulting in vasodilation and consequently improved blood flow to regions of

6750-533: Is no evidence that they change mortality, the risk of revascularization procedures, or the rate of non-fatal myocardial infarction. Antibiotics for secondary prevention of coronary heart disease Early studies suggested that antibiotics might help patients with coronary disease to reduce the risk of heart attacks and strokes. However, a 2021 Cochrane meta-analysis found that antibiotics given for secondary prevention of coronary heart disease are harmful for people with increased mortality and occurrence of stroke. So,

6885-404: Is often a result of treatment by antiarrhythmic drugs such as amiodarone and sotalol , antibiotics such as erythromycin , or antihistamines such as terfenadine . Other drugs which prolong the QT interval include some antipsychotics such as haloperidol and ziprasidone , and the antidepressant citalopram . Lists of medications associated with prolongation of the QT interval such as

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7020-400: Is often used as an antidote in cardiac arrest protocols. The diagnosis of ventricular tachycardia is made based on the rhythm seen on either a 12-lead ECG or a telemetry rhythm strip. It may be very difficult to differentiate between ventricular tachycardia and a wide-complex supraventricular tachycardia in some cases. In particular, supraventricular tachycardias with aberrant conduction from

7155-422: Is placement of an implantable cardioverter-defibrillator (ICD). Also, external defibrillation can be used to restore sinus rhythm. ICDs are commonly used in patients with fainting episodes despite beta blocker therapy, and in patients having experienced a cardiac arrest. As mentioned earlier, ICDs may be used also in patients considered at high risk of life-threatening arrhythmic events. With better knowledge of

7290-626: Is preventing further sequelae of already established disease. Effective lifestyle changes include: Aerobic exercise , like walking, jogging, or swimming, can reduce the risk of mortality from coronary artery disease. Aerobic exercise can help decrease blood pressure and the amount of blood cholesterol (LDL) over time. It also increases HDL cholesterol. Although exercise is beneficial, it is unclear whether doctors should spend time counseling patients to exercise. The U.S. Preventive Services Task Force found "insufficient evidence" to recommend that doctors counsel patients on exercise but "it did not review

7425-453: Is principally diagnosed by measuring the QT interval corrected for heart rate (QTc) on a 12-lead electrocardiogram (ECG). Long QT syndrome is associated with a prolonged QTc, although in some genetically proven cases of LQTS this prolongation can be hidden, known as concealed LQTS. The QTc is less than 450 ms in 95% of normal males, and less than 460 ms in 95% of normal females. LQTS is suggested if

7560-497: Is recommended. Biphasic defibrillation may be better than monophasic. While waiting for a defibrillator, a precordial thump may be attempted (by those who have experience) in those on a heart monitor who are seen going into an unstable ventricular tachycardia. In those with cardiac arrest due to ventricular tachycardia, survival is about 75%. An implantable cardiac defibrillator or medications such as calcium channel blockers or amiodarone may be used to prevent recurrence. While

7695-541: Is termed stable angina and is associated with narrowing of the arteries of the heart . Angina also includes chest tightness, heaviness, pressure, numbness, fullness, or squeezing. Angina that changes in intensity, character or frequency is termed unstable. Unstable angina may precede myocardial infarction . In adults who go to the emergency department with an unclear cause of pain, about 30% have pain due to coronary artery disease. Angina, shortness of breath, sweating, nausea or vomiting, and lightheadedness are signs of

7830-494: Is treated the same as ventricular fibrillation with high-energy (360J with a monophasic defibrillator, or 200J with a biphasic defibrillator) unsynchronised cardioversion ( defibrillation ). They will be unconscious. The shock may be delivered to the outside of the chest using the two pads of an external defibrillator, or internally to the heart by an implantable cardioverter-defibrillator (ICD) if one has previously been inserted. An ICD may also be set to attempt to overdrive pace

7965-434: Is unclear if PCI or CABG in addition to the other treatments improves life expectancy or decreases heart attack risk. In 2015, CAD affected 110 million people and resulted in 8.9 million deaths. It makes up 15.6% of all deaths, making it the most common cause of death globally. The risk of death from CAD for a given age decreased between 1980 and 2010, especially in developed countries . The number of cases of CAD for

8100-609: The CredibleMeds database can be found online. Other causes of acquired LQTS include abnormally low levels of potassium ( hypokalaemia ) or magnesium ( hypomagnesaemia ) within the blood. This can be exacerbated following a sudden reduction in the blood supply to the heart ( myocardial infarction ), low levels of thyroid hormone ( hypothyroidism ), and a slow heart rate ( bradycardia ). Anorexia nervosa has been associated with sudden death, possibly due to QT prolongation. The malnutrition seen in this condition can sometimes affect

8235-515: The Potassium-Channel-Blockers amiodarone, dronedarone, bretylium, sotalol, ibutilide, and dofetilide. Angiotensin-converting-enzyme (ACE) inhibitors and aldosterone antagonists are also sometimes used in this setting. An ICD (implantable cardioverter defibrillator ) is more effective than drug therapy for prevention of sudden cardiac death due to VT and VF, but does not prevent these rhythm from happening. Catheter ablation

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8370-429: The QT interval shortens during exercise, in those with concealed LQT1 exercise or adrenaline infusion may lead to paradoxical prolongation of the QT interval, revealing the underlying condition. International consensus guidelines differ on the degree of QT prolongation required to diagnose LQTS. The European Society of Cardiology recommends that, with or without symptoms or other investigations, LQTS can be diagnosed if

8505-466: The QT intervals of those with and without LQTS. 2.5% of those with genetically proven LQTS have a QT interval within the normal range. Conversely, given the normal distribution of QT intervals, a proportion of healthy people will have a longer QT interval than any arbitrary cutoff. Other factors beyond the QT interval should therefore be taken into account when making a diagnosis, some of which have been incorporated into scoring systems. Long QT syndrome

8640-657: The QTc is longer than these cutoffs. However, as 5% of normal people also fall into this category, some suggest cutoffs of 470 and 480 ms for males and females respectively, corresponding with the 99th centiles of normal values. The major subtypes of inherited LQTS are associated with specific ECG features. LQT1 is typically associated with broad-based T-waves , whereas the T-waves in LQT2 are notched and of lower amplitude, whilst in LQT3

8775-434: The T-waves are often late onset, being preceded by a long isoelectric segment. The Schwartz score has been proposed as a method of combining clinical and ECG factors to assess how likely an individual is to have an inherited form of LQTS. The table below lists the criteria used to calculate the score. In cases of diagnostic uncertainty, other investigations may be helpful to unmask a prolonged QT. In addition to prolonging

8910-411: The United States it results in about 3,500 deaths a year. The condition was first clearly described in 1957. Many people with long QT syndrome have no signs or symptoms. When symptoms occur, they are generally caused by abnormal heart rhythms (arrhythmias), most commonly a form of ventricular tachycardia called Torsades de pointes (TdP). If the arrhythmia reverts to a normal rhythm spontaneously

9045-428: The action potential prolongation occurs to a variable extent in different layers of the heart muscle with longer action potentials in some layers than others. In response to a triggering impulse, the waves of depolarisation will spread through regions with shorter action potentials but block in regions with longer action potentials. This allows the depolarising wavefront to bend around areas of block, potentially forming

9180-420: The affected person may experience lightheadedness (known as presyncope ) or faint which may be preceded by a fluttering sensation in the chest. If the arrhythmia continues, the affected person may experience a cardiac arrest , which if untreated may lead to sudden death. Those with LQTS may also experience non-epileptic seizures as a result of reduced blood flow to the brain during an arrhythmia. Epilepsy

9315-507: The alpha subunit encoded by KCNQ1, is responsible for the potassium current I Ks which is decreased in LQTS. LQT6 is caused by variants in the KCNE2 gene responsible for the potassium channel beta subunit MiRP1 which generates the potassium current I Kr . Variants that decrease this current have been associated with prolongation of the QT interval. However, subsequent evidence such as

9450-413: The arterial walls when consumed in high amounts (and other positive measures towards physical health are not met). High levels of cholesterol in the bloodstream lead to atherosclerosis. With increased levels of LDL in the bloodstream, "LDL particles will form deposits and accumulate within the arterial walls, which will lead to the development of plaques, restricting blood flow". The resultant reduction in

9585-543: The blood (dyslipidemia), type 2 diabetes and being overweight or obese (having excess body fat)" due to lack of exercise and a poor diet. Some other risk factors include high blood pressure , smoking , diabetes , lack of exercise, obesity , high blood cholesterol , poor diet, depression , family history , psychological stress and excessive alcohol . About half of cases are linked to genetics. Smoking and obesity are associated with about 36% and 20% of cases, respectively. Smoking just one cigarette per day about doubles

9720-404: The blood concentration of salts such as potassium, potentially leading to acquired long QT syndrome, in turn causing sudden cardiac death . The malnutrition and associated changes in salt balance develop over a prolonged period of time, and rapid refeeding may further disturb the salt imbalances, increasing the risk of arrhythmias. Care must therefore be taken to monitor electrolyte levels to avoid

9855-557: The body, leading to deafness in the Jervell and Lange-Nielsen form of the condition, and periodic paralysis in the Andersen–Tawil (LQT7) form. While those with long QT syndrome have an increased risk of developing abnormal heart rhythms, the absolute risk of arrhythmias is very variable. The strongest predictor of whether someone will develop TdP is whether they have experienced this arrhythmia or another form of cardiac arrest in

9990-581: The bone morphogenic proteins are members of the TGF-beta superfamily, and likewise impact Treg differentiation. Several of the transcripts ( TMEM98 , NRCAM , SFRP5 , SHISA2 ) are elements of the Wnt signaling pathway, which is a major determinant of Treg differentiation. Limitation of blood flow to the heart causes ischemia (cell starvation secondary to a lack of oxygen) of the heart's muscle cells . The heart's muscle cells may die from lack of oxygen and this

10125-439: The cell, equalising or reversing this polarity, or depolarising the cell. After a contraction has taken place, the cell restores its polarity (or repolarises ) by allowing positively charged ions such as potassium to leave the cell, restoring the membrane to its relaxed, polarised state. In long QT syndrome it takes longer for this repolarisation to occur, shown in individual cells as a longer action potential while being marked on

10260-421: The cell. Some research suggests that delayed afterdepolarisations, occurring after repolarisation has completed, may also play a role in long QT syndrome. This form of afterdepolarisation originates from the spontaneous release of calcium from the intracellular calcium store known as the sarcoplasmic reticulum , forcing calcium out of cell through the sodium calcium exchanger in exchange for sodium, generating

10395-473: The channel of an artery, causing partial obstruction to blood flow. People with coronary artery disease might have just one or two plaques or might have dozens distributed throughout their coronary arteries . A more severe form is chronic total occlusion (CTO) when a coronary artery is completely obstructed for more than 3 months. Microvascular angina is a type of angina pectoris in which chest pain and chest discomfort occur without signs of blockages in

10530-516: The circulating immune system would be related to the immune synapse . One of the most differentially expressed genes, fibromodulin (FMOD), which is increased 2.8-fold in CAD, is found mainly in connective tissue and is a modulator of the TGF-beta signaling pathway. However, not all of the RNA changes may be related to the immune synapse. For example, Nebulette , the most down-regulated transcript (2.4-fold),

10665-594: The complications of refeeding syndrome . Factors which prolong the QT interval are additive, meaning that a combination of factors (such as taking a QT-prolonging drug and having low levels of potassium) can cause a greater degree of QT prolongation than each factor alone. This also applies to some genetic variants which by themselves only minimally prolong the QT interval but can make people more susceptible to significant drug-induced QT prolongation. The various forms of long QT syndrome, both congenital and acquired, produce abnormal heart rhythms (arrhythmias) by influencing

10800-413: The condition based on the clinical features (and named after those who first described the condition) and subdivided by the underlying genetic variant. The most common of these, accounting for 99% of cases, is Romano–Ward syndrome (genetically LQT1-6 and LQT9-16), an autosomal dominant form in which the electrical activity of the heart is affected without involving other organs. A less commonly seen form

10935-465: The corrected QT interval is longer than 480ms. They recommend that a diagnosis can be considered in the presence of a QTc of greater than 460 ms if unexplained syncope has occurred. The Heart Rhythm Society guidelines are more stringent, recommending QTc cutoff of greater than 500 ms in the absence of other factors that prolong the QT, or greater than 480 ms with syncope. Both sets of guidelines agree that LQTS can also be diagnosed if an individual has

11070-523: The delayed potassium rectifier current I Ks responsible for the repolarisation phase of the cardiac action potential . Variants in KCNQ1 that decrease I Ks (loss of function variants) slow the repolarisation of the action potential. This causes the LQT1 subtype of Romano–Ward syndrome when a single copy of the variant is inherited (heterozygous, autosomal dominant inheritance). Inheriting two copies of

11205-409: The diameter of their blood vessels, leading to decreased progression of atherosclerosis. In contrast, females who had high levels of work-related stress experienced a decrease in the diameter of their blood vessels and significantly increased disease progression. Having a type A behavior pattern , a group of personality characteristics including time urgency, competitiveness, hostility, and impatience,

11340-552: The different variables above. A notable example is Framingham Score , used in the Framingham Heart Study . It is mainly based on age, gender, diabetes, total cholesterol, HDL cholesterol, tobacco smoking, and systolic blood pressure. When predicting risk in younger adults (18–39 years old), the Framingham Risk Score remains below 10–12% for all deciles of baseline-predicted risk. Polygenic score

11475-512: The electrical signals used to coordinate individual heart cells. The common theme is a prolongation of the cardiac action potential – the characteristic pattern of voltage changes across the cell membrane that occur with each heart beat. Heart cells when relaxed normally have fewer positively charged ions on the inner side of their cell membrane than on the outer side, referred to as the membrane being polarised . When heart cells contract , positively charged ions such as sodium and calcium enter

11610-421: The evidence for the effectiveness of physical activity to reduce chronic disease, morbidity, and mortality", only the effectiveness of counseling itself. The American Heart Association , based on a non-systematic review, recommends that doctors counsel patients on exercise. Psychological symptoms are common in people with CHD, and while many psychological treatments may be offered following cardiac events, there

11745-793: The evidence is weak. Specifically, its use does not change the risk of death in this group. In those who have had a stent, more than 12 months of clopidogrel plus aspirin does not affect the risk of death. Revascularization for acute coronary syndrome has a mortality benefit. Percutaneous revascularization for stable ischaemic heart disease does not appear to have benefits over medical therapy alone. In those with disease in more than one artery, coronary artery bypass grafts appear better than percutaneous coronary interventions . Newer "anaortic" or no-touch off-pump coronary artery revascularization techniques have shown reduced postoperative stroke rates comparable to percutaneous coronary intervention. Hybrid coronary revascularization has also been shown to be

11880-1118: The future, and one in three healthy 40-year-old females. It is the most common reason for death of males and females over 20 years of age in the United States. Long QT syndrome Long QT syndrome ( LQTS ) is a condition affecting repolarization (relaxing) of the heart after a heartbeat , giving rise to an abnormally lengthy QT interval . It results in an increased risk of an irregular heartbeat which can result in fainting , drowning , seizures , or sudden death . These episodes can be triggered by exercise or stress. Some rare forms of LQTS are associated with other symptoms and signs including deafness and periods of muscle weakness . Long QT syndrome may be present at birth or develop later in life. The inherited form may occur by itself or as part of larger genetic disorder . Onset later in life may result from certain medications, low blood potassium , low blood calcium , or heart failure . Medications that are implicated include certain antiarrhythmics , antibiotics , and antipsychotics . LQTS can be diagnosed using an electrocardiogram (EKG) if

12015-526: The genes responsible for calmodulin ( CALM1, CALM2, and CALM3 respectively). Calmodulin interacts with several ion channels and its roles include modulation of the L-type calcium current in response to calcium concentrations, and trafficking the proteins produced by KCNQ1 and thereby influencing potassium currents. The precise mechanisms by which means these genetic variants prolong the QT interval remain uncertain. Jervell and Lange–Nielsen syndrome (JLNS)

12150-546: The genetics underlying LQTS, more precise treatments hopefully will become available. Genotype and QTc interval duration are the strongest predictors of outcome for patients with LQTS. 2022 European Society of Cardiology clinical practice guidelines have endorsed the use of independently validated risk score calculator, called 1-2-3-LQTS-Risk Calculator, which allows to calculate individual 5-year risk of life-threatening arrhythmic events. For people who experience cardiac arrest or fainting caused by LQTS and who are untreated,

12285-549: The girl's parents reported that her older brother, also deaf, had previously died after a terrible fright. This was several decades before the ECG was invented, but is likely the first described case of Jervell and Lange-Nielsen syndrome. In 1957, the first case documented by ECG was described by Anton Jervell and Fred Lange-Nielsen , working in Tønsberg , Norway . Italian pediatrician Cesarino Romano, in 1963, and Irish pediatrician Owen Conor Ward, in 1964, separately described

12420-507: The group of abnormal cardiac rhythms originating from the ventricle, which includes ventricular tachycardia, ventricular fibrillation, and torsades de pointes . In those who have normal blood pressure and strong pulse , the antiarrhythmic medication procainamide may be used. Otherwise, immediate cardioversion is recommended, preferably with a biphasic DC shock of 200 joules. In those in cardiac arrest due to ventricular tachycardia, cardiopulmonary resuscitation (CPR) and defibrillation

12555-436: The harms most favorably in people at high risk for a cardiovascular event, where high risk is defined as at least a 3% chance over a five-year period, but others with lower risk may still find the potential benefits worth the associated risks. Clopidogrel plus aspirin (dual anti-platelet therapy) reduces cardiovascular events more than aspirin alone in those with a STEMI . In others at high risk but not having an acute event,

12690-450: The heart affected by atherosclerotic plaque. Stable coronary artery disease (SCAD) is also often called stable ischemic heart disease (SIHD). A 2015 monograph explains that "Regardless of the nomenclature, stable angina is the chief manifestation of SIHD or SCAD." There are U.S. and European clinical practice guidelines for SIHD/SCAD. In patients with non-severe asymptomatic aortic valve stenosis and no overt coronary artery disease,

12825-466: The heart muscle). Diagnosis is clear-cut if ECGs show elevation of the " ST segment ", which in the context of severe typical chest pain is strongly indicative of an acute myocardial infarction (MI); this is termed a STEMI (ST-elevation MI) and is treated as an emergency with either urgent coronary angiography and percutaneous coronary intervention (angioplasty with or without stent insertion) or with thrombolysis ("clot buster" medication), whichever

12960-428: The heart muscle). If part of the heart seems to receive an insufficient blood supply, coronary angiography may be used to identify stenosis of the coronary arteries and suitability for angioplasty or bypass surgery . In minor to moderate cases, nitroglycerine may be used to alleviate acute symptoms of stable angina or may be used immediately before exertion to prevent the onset of angina. Sublingual nitroglycerine

13095-787: The heart's blood supply due to atherosclerosis in coronary arteries "causes shortness of breath, angina pectoris (chest pains that are usually relieved by rest), and potentially fatal heart attacks (myocardial infarctions)". The heritability of coronary artery disease has been estimated between 40% and 60%. Genome-wide association studies have identified over 160 genetic susceptibility loci for coronary artery disease. Several RNA Transcripts associated with CAD - FoxP1 , ICOSLG , IKZF4/Eos , SMYD3 , TRIM28 , and TCF3/E2A are likely markers of regulatory T cells (Tregs), consistent with known reductions in Tregs in CAD. The RNA changes are mostly related to ciliary and endocytic transcripts, which in

13230-520: The immune synapse, there were numerous transcripts that related directly to T cell function and the control of differentiation. Butyrophilin is a co-regulator for T cell activation. Fibromodulin is a modulator of the TGF-beta signaling pathway, a primary determinant of Tre differentiation. Further impact on the TGF-beta pathway is reflected in concurrent changes in the BMP receptor 1B RNA (BMPR1B), because

13365-428: The increased troponin T (above 14 pg/mL) was found associated with an increased 5-year event rate of ischemic cardiac events ( myocardial infarction , percutaneous coronary intervention , or coronary artery bypass surgery ). Diagnosis of acute coronary syndrome generally takes place in the emergency department , where ECGs may be performed sequentially to identify "evolving changes" (indicating ongoing damage to

13500-404: The larger coronary arteries of their hearts when an angiogram (coronary angiogram) is being performed. The exact cause of microvascular angina is unknown. Explanations include microvascular dysfunction or epicardial atherosclerosis. For reasons that are not well understood, females are more likely than males to have it; however, hormones and other risk factors unique to females may play

13635-438: The monomorphic form coincides with little or no increased risk of sudden cardiac death. In general, idiopathic ventricular tachycardia occurs in younger individuals diagnosed with VT. While the causes of idiopathic VT are not known, in general it is presumed to be congenital, and can be brought on by any number of diverse factors. Therapy may be directed either at terminating an episode of the abnormal heart rhythm or at reducing

13770-563: The more common variant of LQTS with normal hearing, later called Romano-Ward syndrome. The establishment of the International Long-QT Syndrome Registry in 1979 allowed numerous pedigrees to be evaluated in a comprehensive manner. This helped in detecting many of the numerous genes involved. Transgenic animal models of the LQTS helped define the roles of various genes and hormones involved, and recently experimental pharmacological therapies to normalize

13905-633: The most common symptom reported by females of all races is shortness of breath. Other symptoms more commonly reported by females than males are extreme fatigue, sleep disturbances, indigestion, and anxiety. However, some females experience irregular heartbeat, dizziness, sweating, and nausea. Burning, pain, or pressure in the chest or upper abdomen that can travel to the arm or jaw can also be experienced in females, but females less commonly report it than males. Generally, females experience symptoms 10 years later than males. Females are less likely to recognize symptoms and seek treatment. Coronary artery disease

14040-412: The myocardium. Stable angina is short-term chest pain during physical exertion caused by an imbalance between myocardial oxygen supply and metabolic oxygen demand. Various forms of cardiac stress tests may be used to induce both symptoms and detect changes by way of electrocardiography (using an ECG), echocardiography (using ultrasound of the heart) or scintigraphy (using uptake of radionuclide by

14175-507: The next heartbeat is due. Under the right conditions, reactivation of these currents, facilitated by the sodium-calcium exchanger, can cause further depolarisation of the cell. The early afterdepolarisations triggering arrhythmias in long QT syndrome tend to arise from the Purkinje fibres of the cardiac conduction system. Early afterdepolarisations may occur as single events, but may occur repeatedly leading to multiple rapid activations of

14310-453: The other hand, is most commonly caused by abnormalities of ventricular muscle repolarization. The predisposition to this problem usually manifests on the ECG as a prolongation of the QT interval. QT prolongation may be congenital or acquired. Congenital problems include long QT syndrome and catecholaminergic polymorphic ventricular tachycardia . Acquired problems are usually related to drug toxicity or electrolyte abnormalities, but can occur as

14445-424: The past. Those with LQTS who have experienced syncope without an ECG having been recorded at the time are also at higher risk, as syncope in these cases is frequently due to an undocumented self-terminating arrhythmia. In addition to a history of arrhythmias, the extent to which the QT is prolonged predicts risk. While some have QT intervals that are very prolonged, others have only slight QT prolongation, or even

14580-485: The potassium channel that carries the rapid inward rectifier current I Kr . This current contributes to the terminal repolarisation phase of the cardiac action potential, and therefore the length of the QT interval. The LQT3 subtype of Romano–Ward syndrome is caused by variants in the SCN5A gene located on chromosome 3p22–24. SCN5A encodes the alpha subunit of the cardiac sodium channel, Na V 1.5, responsible for

14715-416: The proteasomal regulator SIAH3 , and the ubiquitin ligase MARCHF10 . On the ciliary aspect of the immune synapse, several of the modulated transcripts are related to ciliary length and function. Stereocilin is a partner to mesothelin , a related super-helical protein, whose transcript is also modulated in CAD. DCDC2 , a double-cortin protein, is a modulator of ciliary length. In the signaling pathways of

14850-466: The rare coronary artery disease that is more common in females, as mentioned, is a diagnosis of exclusion. Therefore, usually, the same tests are used as in any person suspected of having coronary artery disease: Stable angina is the most common manifestation of ischemic heart disease, and is associated with reduced quality of life and increased mortality. It is caused by epicardial coronary stenosis which results in reduced blood flow and oxygen supply to

14985-414: The relatively common finding of variants in the gene in those without long QT syndrome, and the general need for a second stressor such as hypokalaemia to be present to reveal the QT prolongation, has suggested that this gene instead represents a modifier to susceptibility to QT prolongation. Some therefore dispute whether variants in KCNE2 are sufficient to cause Romano-Ward syndrome by themselves. LQT9

15120-451: The resting QT interval, LQTS may affect how the QT changes in response to exercise and stimulation by catecholamines such as adrenaline. Provocation tests, in the form of exercise tolerance tests or direct infusion of adrenaline, can be used to detect these abnormal responses. These investigations are most useful for identifying those with concealed congenital Type 1 LQTS 1 (LQT1) who have a normal QT interval at rest. While in healthy persons

15255-460: The risk of CAD. Lack of exercise has been linked to 7–12% of cases. Exposure to the herbicide Agent Orange may increase risk. Rheumatologic diseases such as rheumatoid arthritis , systemic lupus erythematosus , psoriasis , and psoriatic arthritis are independent risk factors as well. Job stress appears to play a minor role accounting for about 3% of cases. In one study, females who were free of stress from work life saw an increase in

15390-464: The risk of another VT episode. The treatment for stable VT is tailored to the specific person, with regard to how well the individual tolerates episodes of ventricular tachycardia, how frequently episodes occur, their comorbidities, and their wishes. Individuals with pulseless VT or unstable VT are hemodynamically compromised and require immediate electric cardioversion to shock them out of the VT rhythm. If

15525-493: The risk of cardiovascular disease and death. Vegetarians have a lower risk of heart disease, possibly due to their greater consumption of fruits and vegetables. Evidence also suggests that the Mediterranean diet and a high fiber diet lower the risk. The consumption of trans fat (commonly found in hydrogenated products such as margarine ) has been shown to cause a precursor to atherosclerosis and increase

15660-552: The risk of coronary artery disease by about 25%. Life's Essential 8 are the key measures for improving and maintaining cardiovascular health, as defined by the American Heart Association. AHA added sleep as a factor influencing heart health in 2022. Most guidelines recommend combining these preventive strategies. A 2015 Cochrane Review found some evidence that counseling and education to bring about behavioral change might help in high-risk groups. However, there

15795-410: The risk of coronary artery disease. Evidence does not support a beneficial role for omega-3 fatty acid supplementation in preventing cardiovascular disease (including myocardial infarction and sudden cardiac death ). There is tentative evidence that intake of menaquinone ( Vitamin K 2 ), but not phylloquinone ( Vitamin K 1 ), may reduce the risk of CAD mortality . Secondary prevention

15930-521: The risk of death within 15 years is around 50%. With careful treatment this decreases to less than 1% over 20 years. Those who exhibit symptoms before the age of 18 are more likely to experience a cardiac arrest. Inherited LQTS is estimated to affect between one in 2,500 and 7,000 people. The first documented case of LQTS was described in Leipzig by Meissner in 1856, when a deaf girl died after her teacher yelled at her. Soon after being notified,

16065-443: The risk of death within 15 years is greater than 50%. With proper treatment this decreases to less than 1% over 20 years. Long QT syndrome is estimated to affect 1 in 7,000 people. Females are affected more often than males. Most people with the condition develop symptoms before they are 40 years old. It is a relatively common cause of sudden death along with Brugada syndrome and arrhythmogenic right ventricular dysplasia . In

16200-469: The risk of stress-induced arrhythmias. Nadolol , a powerful non-selective beta blocker , has been shown to reduce the arrhythmic risk in all three main genotypes (LQT1, LQT2, and LQT3). Genotype and QT interval duration are independent predictors of recurrence of life-threatening events. Arrhythmia termination involves stopping a life-threatening arrhythmia once it has already occurred. One effective form of arrhythmia termination in individuals with LQTS

16335-492: The risk profile. Noninvasive imaging options include; Computed tomography angiography (CTA) (anatomical imaging, best test in patients with low-risk profile to "rule out" the disease), positron emission tomography (PET), single-photon emission computed tomography (SPECT)/nuclear stress test/myocardial scintigraphy and stress echocardiography (the three latter can be summarized as functional noninvasive methods and are typically better to "rule in"). Exercise ECG or stress test

16470-875: The shoulder, arm, back, neck, or jaw. Occasionally it may feel like heartburn . In stable angina , symptoms occur with exercise or emotional stress , last less than a few minutes, and improve with rest. Shortness of breath may also occur and sometimes no symptoms are present. In many cases, the first sign is a heart attack . Other complications include heart failure or an abnormal heartbeat . Risk factors include high blood pressure , smoking , diabetes , lack of exercise, obesity , high blood cholesterol , poor diet, depression , and excessive alcohol consumption. A number of tests may help with diagnosis including: electrocardiogram , cardiac stress testing , coronary computed tomographic angiography , biomarkers ( high-sensitivity cardiac troponins ) and coronary angiogram , among others. Ways to reduce CAD risk include eating

16605-414: The smooth, elastic lining inside a coronary artery (the arteries that supply blood to the heart muscle) develops atherosclerosis . With atherosclerosis, the artery's lining becomes hardened, stiffened, and accumulates deposits of calcium, fatty lipids, and abnormal inflammatory cells – to form a plaque . Calcium phosphate (hydroxyapatite) deposits in the muscular layer of the blood vessels appear to play

16740-520: The sodium current I Na which depolarises cardiac cells at the start of the action potential. Cardiac sodium channels normally inactivate rapidly, but the mutations involved in LQT3 slow their inactivation leading to a small sustained 'late' sodium current. This continued inward current prolongs the action potential and thereby the QT interval. While some variants in SCN5A cause LQT3, other variants can cause quite different conditions. Variants causing

16875-470: The structure of the heart and autism spectrum disorder . LQT1 is the most common subtype of Romano–Ward syndrome, responsible for 30 to 35% of all cases. The gene responsible, KCNQ1, has been isolated to chromosome 11p 15.5 and encodes the alpha subunit of the KvLQT1 potassium channel. This subunit interacts with other proteins (in particular, the minK beta subunit) to create the channel, which carries

17010-413: The structure of the heart are commonly seen including ventricular septal defect , tetralogy of Fallot , and hypertrophic cardiomyopathy . The condition presents early in life and the average life expectancy is 2.5 years with death most commonly caused by ventricular arrhythmias. Many children with Timothy syndrome who survive longer than this have features of autism spectrum disorder . Timothy syndrome

17145-572: The surface ECG as a long QT interval. The prolonged action potentials can lead to arrhythmias through several mechanisms. The arrhythmia characteristic of long QT syndrome, torsades de pointes , starts when an initial action potential triggers further abnormal action potentials in the form of afterdepolarisations . Early afterdepolarisations, occurring before the cell has fully repolarised, are particularly likely to be seen when action potentials are prolonged, and arise due to reactivation of calcium and sodium channels that would normally switch off until

17280-406: The use of antibiotics is not currently supported for preventing secondary coronary heart disease. A thorough systematic review found that indeed there is a link between a CHD condition and brain dysfunction in females. Consequently, since research is showing that cardiovascular diseases, like CHD, can play a role as a precursor for dementia, like Alzheimer's disease, individuals with CHD should have

17415-410: The use of medications or surgical procedures that attack the underlying cause of the arrhythmias associated with LQTS. Since the cause of arrhythmias in LQTS is early afterdepolarizations (EADs), and they are increased in states of adrenergic stimulation, steps can be taken to blunt adrenergic stimulation in these individuals. These include administration of beta receptor blocking agents , which decreases

17550-556: The variant (homozygous, autosomal recessive inheritance) leads to the more severe Jervell and Lange–Nielsen syndrome. Conversely, variants in KCNQ1 that increase I Ks lead to more rapid repolarisation and the short QT syndrome . The LQT2 subtype is the second-most common form of Romano–Ward syndrome, responsible for 25 to 30% of all cases. It is caused by variants in the KCNH2 gene (also known as hERG ) on chromosome 7 which encodes

17685-469: The variant is inherited. JLNS is generally associated with a higher risk of arrhythmias than most other forms of LQTS. LQT7, also known as Andersen–Tawil syndrome , is characterised by a triad of features – in addition to a prolonged QT interval, those affected may experience intermittent weakness often occurring at times when blood potassium concentrations are low (hypokalaemic periodic paralysis), and characteristic facial and skeletal abnormalities such as

17820-494: The ventricle. Pacing the ventricle at a rate faster than the underlying tachycardia can sometimes be effective in terminating the rhythm. If this fails after a short trial, the ICD will usually stop pacing, charge up and deliver a defibrillation grade shock. For those who are stable with a monomorphic waveform the medications procainamide or sotalol may be used and are better than lidocaine . Evidence does not show that amiodarone

17955-612: The ventricle. The most common cause of monomorphic ventricular tachycardia is scarring of the heart muscle from a previous myocardial infarction (heart attack). This scar cannot conduct electrical activity, so there is a potential circuit around the scar that results in the tachycardia. This is similar to the re-entrant circuits that are the cause of atrial flutter and the re-entrant forms of supraventricular tachycardia . Other rarer congenital causes of monomorphic VT include right ventricular dysplasia, and right and left ventricular outflow tract VT. Polymorphic ventricular tachycardia, on

18090-414: The ventricles, generating QRS complexes with normal or aberrant supraventricular morphology (ventricular capture). Or, those impulses can be merged with complexes that are originated in the ventricle and produce a summation pattern (fusion complexes). Less common is ventricular tachycardia that occurs in individuals with structurally normal hearts. This is known as idiopathic ventricular tachycardia and in

18225-501: Was insufficient evidence to show an effect on mortality or actual cardiovascular events. In diabetes mellitus , there is little evidence that very tight blood sugar control improves cardiac risk although improved sugar control appears to decrease other problems such as kidney failure and blindness . A 2024 study published in The Lancet Diabetes & Endocrinology found that the oral glucose tolerance test (OGTT)

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