Long QTc and Torsades de Pointes in Human Immunodeficiency Virus Disease

Three patients with human immunodeficiency virus (HIV) infection presented with QT_c prolongation (> 440 ms) and torsades de pointes. We sought to evaluate the etiology of the long QT syndrome in these patients without previously identified causes for QT_c prolongation, and determine the prevalence among patients with HIV infection. The three index patients underwent: (1) left stellate ganglion block; (2) β-blocker challenge; and (3) electrocardiographic stress testing. QT_c interval was measured before and after intervention. We undertook a retrospective analysis of prevalence of QT_c prolongation among all patients with computerized ECGs over a 6-month period at one institution and compared it to the prevalence in hospitalized patients with HIV disease. Thirty-four thousand one hundred eighty-one patients with computerized ECGs were screened for QT_c prolongation. Forty-two hospitalized patients with HIV disease had computerized ECG during the same 6-month period. In the three index patients, the QT_c failed to shorten with left stellate ganglion blockade, β-blocker challenge, or stress testing, suggesting an acquired form of the long QT syndrome in these patients with HIV disease. None had previously recognized acquired causes of QT_c prolongation. Mexiletine hydrochloride was useful in preventing recurrences of torsades de pointes. We observed a 7.0% prevalence of QT_c prolongation among all patients screened. Hospitalized patients with HIV disease (n = 42) during this same period, demonstrated an increased prevalence of QT_c prolongation (28.6%, P = 0.002). Patients with HIV disease have a significantly higher prevalence of QT_c prolongation than a general hospital-based population, may have an unrecognized acquired form of the long QT syndrome, and are at risk for torsades de pointes.     

Torsade de pointes caused by polypharmacy and substance abuse in a patient with human immunodeficiency virus

Drug-induced QT prolongation is a potentially dangerous adverse effect of some medication combinations. When QT prolongation progresses to torsade de pointes, life-threatening or fatal outcomes may result. A 57-year-old man with a history of human immunodeficiency syndrome on abacavir, nevirapine, tenofovir, voriconazole, and methadone presented to the emergency department with a chief complaint of new-onset seizures. The physical exam was unremarkable. The electrocardiogram demonstrated sinus bradycardia and a prolonged QT_c interval of 690 ms. In the emergency department, he had several episodes of torsade de pointes (TdP) and ventricular tachycardia that resolved spontaneously. These episodes were accompanied by an alteration in mentation and generalized twitching. Magnesium and amiodarone were effective in terminating the dysrhythmia. The patient had multiple risk factors for prolonged QT syndrome including human immunodeficiency virus infection, methadone therapy, and polypharmacy leading to potential drug interactions. Physicians must be aware of multidrug interactions potentiating QT prolongation and leading to torsade de pointes.     

Genotype-specific clinical manifestation in long QT syndrome

The congenital form of long QT syndrome (LQTS) is characterized by QT prolongation in the electrocardiogram (ECG) and a polymorphic ventricular tachycardia, Torsade de Pointes (TdP) mainly as a result of an increased sympathetic tone during exercise or mental stress. Recent genetic studies have so far identified seven forms of congenital LQTS caused by mutations in genes of the potassium and sodium channels or membrane adapter located on chromosomes 3, 4, 7, 11, 17 and 21. It is of particular importance to examine the genotype-phenotype correlation, especially in the LQT1, LQT2 and LQT3 forms of LQTS, which make up more than 90% of genotyped patients with LQTS, because it would enable us to manage and treat genotyped patients more effectively.     

Ambulatory Assessment of the QT Interval in Patients with Hypertrophic Cardiomyopathy: Risk Stratification and Effect of Low Dose Amiodarone

This study aims to assess the dynamics of the QT interval in patients with hypertrophic cardiomyopathy (HCM). Three consecutive QT intervals and the preceding RR intervals were measured on 24-hour ambulatory electrocardiograms at 30-minute intervals in ten high risk patients with HCM (sudden cardiac death [SCD] and/or documented ventricular fibrillation), aged 29 ± 17 years, compared with ten age and sex matched low risk patients with HCM (no syncope, no adverse family history, and no ventricular tachycardia on Holter monitoring), and ten normal subjects. Another ten patients who were on amiodarone therapy (200-mg daily) were also studied. Patients witb intraventricular conduction defects were excluded. There were 4,424 pairs of QT intervals and their preceding RR intervals were measured in this study. A nonsignificant prolongation in the QT interval and a significant prolongation in QT_c values (Bazett's and Fridericia's formulas) were demonstrated in patients with HCM compared with normals. There were no significant differences in the QT and QT_c between high and low risk patients. The slope of regression line for the QT against RR interval was significantly different between normals and HCM (0.1583 ± 0.040 vs 0.2017 ± 0.043. P < 0.05), but not between high and low risk patients. Amiodarone significantly prolonged the QT and QT_c without significantly altering the slope of the regression line (0.2017 ± 0.043 vs 0.2099 ± 0.037, NS). Our findings support the observations that there is a prolonged QT interval in patients with HCM and that there is no significant use dependent effect of amiodarone on ventricular repolarization. In conclusion, ambulatory assessment of the QT interval provides an alternative method for the assessment of ventricular repolarization and for the assessment of use dependent effects of anti arrhythmic drugs on ventricular repolarization during normal daily activities. However, this method does not help in the identification of patients at high risk of SCD in HCM.     

Genotype-specific clinical manifestation in long QT syndrome

The congenital form of long QT syndrome (LQTS) is characterized by QT prolongation in the electrocardiogram (ECG) and a polymorphic ventricular tachycardia, Torsade de Pointes (TdP) mainly as a result of an increased sympathetic tone during exercise or mental stress. Recent genetic studies have so far identified seven forms of congenital LQTS caused by mutations in genes of the potassium and sodium channels or membrane adapter located on chromosomes 3, 4, 7, 11, 17 and 21. It is of particular importance to examine the genotype–phenotype correlation, especially in the LQT1, LQT2 and LQT3 forms of LQTS, which make up more than 90% of genotyped patients with LQTS, because it would enable us to manage and treat genotyped patients more effectively.     

Electrophysiologic parameters and predisposing factors in the generation of drug-induced Torsade de Pointes arrhythmias

When a new (cardiovascular) drug shows signs of QT interval prolongation on the ECG (delay in repolarization time), the regulatory agencies demand screening of its possible proarrhythmic potential before approving it for clinical practice. In this review, identified predisposing factors have been related to specific electrophysiological parameters, allowing quantification of their contribution to Torsade de Pointes arrhythmias. In addition, arrhythmogenic mechanisms involved in the initiation and perpetuation of drug-induced Torsade de Pointes are discussed.     

A 2015 focus on preventing drug-induced arrhythmias

Drug-induced Torsade de Pointes arrhythmia is a life-threatening adverse effect feared by pharmaceutical companies. For the last decade, the cardiac safety guidelines have imposed human ether-a-go-go-related gene channel blockade and prolongation of QT interval as surrogates for proarrhythmic risk propensity of a new chemical entity. Suffering from a lack of specificity, this assessment strategy led to a great amount of false positive outcomes. Therefore, this review will discuss new pharmaceutical strategies: the cardiac safety proposal that recently emerged, the Comprehensive in vitro Proarrhythmia Assay, combining in vitro assays that integrate effects on main cardiac ion channels, with computational models of human ventricular action potential as well as assays using human stem cell-derived cardiomyocytes for an improved prediction of drug’s proarrhythmic liability, alternative pharmacological perspectives as well as the current treatment of drug-induced long QT syndrome.     

QT and QT-peak interval measurements. A methodological study in patients with subarachnoid haemorrhage compared to a reference group

Summary. To study the properties of QT and QT-peak intervals, ECGs were compared between 56 consecutive patients who were suffering from subarachnoid haemorrhage (SAH) and 50 reference subjects. The routine QT_C interval was compared to the mean QT_C from all of the 12 leads with identifiable U waves and to the mean QT-peak_e. The interval between peak and end of T(T_p- T_e) was subsequently calculated. In the reference group the mean QT-peak correlated with the mean QT(r=0.925). The rate-dependence of the mean QT-peak was not different from that of the mean QT and showed the same correlation (r= -0.607 and -0.630, respectively). No rate-dependence for the T_p-T_c interval could be demonstrated. Following SAH, ECG abnormalities were most pronounced after 8–9 days, and increased with age and the degree of cerebral dysfunction. Two patient groups, where the mean QT_c of each particular patient was either below (n=27) or above (n=29) the reference limit, were analysed. For the group without an abnormally prolonged mean QT_c, the average of the individual mean QT_c was significantly longer than in the reference group. Both groups had longer mean QT-peak_c intervals than the reference group. About 70% of the patients with an abnormally prolonged mean QT_C also had a prolonged mean QT-peak_c interval, while the rest had a prolonged T_p-T_c interval; simultaneous prolongation of these two intervals also occurred. Prolongation of the T_p-T_c interval did not occur in the group without an abnormally prolonged mean QT_c. Routine QT_C and mean QT-peak_c had sensitivities of 96% and 67% respectively, specificities of 76% and 96% and predictive values of 81% and 95%. In conclusion, the routine QT_C measurements, without reference to an identified U wave, may result in falsely prolonged estimates of cardiac repolarization time. In this respect the mean QT-peak_c may provide additional information. In the majority of patients the prolonged mean QT_C was dependent on a disturbed rate-dependent function (prolonged mean QT-peak_c) while some patients had an increased asymmetry of the repolarization process within the myocardium (prolonged T_p-T_c).     

Differential Response of QTU Interval to Exercise, Isoproterenol, and Atrial Pacing in Patients with Congenital Long QT Syndrome

Sympathetic stimulation is well known to contribute to the genesis of QTU prolongation and ventricular lachyarrhythmias in patients with congenital long QT syndrome. In this study, we performed exercise treadmill testing, isoproterenol infusion (1–2 μg/min), and right atrial pacing (cycle length 500 msec) in 11 patients with congenital long QT (LQT) syndrome (LQT group) and in 12 age- and sex-matched controls (control group). The responses of the corrected QT (QT_c; Bazett's method) interval and the TU wave complex tvere evaluated. The QT_c interval was prolonged from 482 ± 63 msec^1/2 to 548 ± 28 msec^1/2 by exercise in the LQT group (n = 11; P < 0.005), and this was associated with fusion of the T waves with enlarged U waves, whereas the QT_c interval did not increase with exercise in the control group (n = 12; 402 ± 19 msec^1/2 vs 409 ± 22 msec^1/2). The QT_c interval was also prolonged from 466 ± 50 msec^1/2 to 556 ± 33 msec^1/2 by isoproterenol in the LQT group (n = 7; P < 0.005) in association with morphological changes of the TU wave complex like those seen with exercise, whereas it was only slightly increased from 399 ± 10 msec^1/2 to 436 ± 13 msec^1/2 by isoproterenol in the control group (n = 77; P < 0.001). However, the QT_c interval did not increase with atrial pacing in the LQT group (n = 8; 476 ± 57 msec^1/2 vs 486 ± 59 msec^1/2), whereas it was slightly increased from 400 ± 21 msec^1/2 to 426 ± 18 msec^1/2 by atrial paring in (he control group (n = 8; P < 0.005). These results suggest that sympathetic stimulation plays an important role in the QTU prolongation and marked TU wave complex abnormalities in patients with congenital long QT syndrome.     

Drug-induced q-T prolongation

Drug therapy may induce Q-T prolongation by alteration of potassium ion currents in cardiac cells, resulting in abnormal repolarization. Q-T prolongation, whether congenital or acquired, has been associated with the development of the malignant dysrhythmia Torsade de Pointes (TdP), which may result in sudden death. Re-cent regulatory actions and drug withdrawals due to Q-T prolongation or TdP have focused attention on this issue. Although our understanding of the pathophysiology continues to evolve, both patient and medication factors contribute to the individual risk of drug-induced Q-T prolongation or TdP. The clinician should be aware of these issues when prescribing new drugs and should weigh the risks and benefits carefully when prescribing drugs known to prolong the Q-T interval.     

Influence of Early Coronary Reperfusion on QT Interval Dispersion After Acute Myocardial Infarction

We studied the influence of early coronary reperfusion on QT interval dispersion in patients with acute myocardial infarction (MI). Tbere were 54 males and 18 females witb a mean age of 60 ± 10 years. Of the 51 patients with recanalization of the infarct related vessel in the recovery phase, 28 (group A) had early coronary reperfusion (5.5 ± 2.7 bours), 23 other patients (group B) were not confirmed with early coronary reperfusion. Twenty-one patients (group C) did not undergo recanalization of the infarct related vessel in the recovery phase. Corrected QT (QT_c) maximum, QT_c minimum, and QT_C dispersion calculated as tbe difference between the maximum and minimum QT_c intervals, were compared among these three groups at both acute and recovery phase. At the acute phase after MI, there were no significant differences in the QT_c maximum, QT_c minimum, QT dispersion, and QT_c dispersion among these three groups. At the recovery phase after MI, there were also no significant differences in the QTc maximum and QTc minimum. However, there were significant differences in the QT dispersion (0.035 ± 0.010 in group A, 0.049 ± 0.015 in group B, and 0.061 ± 0.031 s in group C, respectively; P = 0.0001), and QT_c dispersion (0.038 ± 0.012 in group A, 0.050 ± 0.015 in group B, and 0.063 ± 0.032 s in group C, respectively; P = 0.0003) among the three groups. Comparison of QT_c dispersion between acute and recovery phase revealed significant reduction from acute to recovery phase in group A. The number of premature ventricular contraction was lower in groups A and B than group C. In summary, early coronary reperfusion may reduce electrophysiological instability by reducing QT dispersion in the recovery phase after acute MI.     

Ciprofloxacin- and hypocalcemia-induced torsade de pointes triggered by hemodialysis

Torsade de pointes is a polymorphic form of ventricular tachycardia associated with prolongation of the QT interval, which may be either congenital or acquired. Etiologies for the acquired forms include drug effects, hypokalemia, hypomagnesemia, hypocalcemia, starvation, sick sinus syndrome, and atrioventricular block. We present a 76-year-old man with acute on chronic renal failure, hypocalcemia, on ciprofloxacin, and a prolonged QT interval with torsade de pointes triggered by hemodialysis. The QT prolongation was corrected by treating the hypocalcemia. Hypocalcemia and ciprofloxacin are known to independently cause prolonged QT interval and torsade de pointes; our case illustrates that dialysis can trigger torsade on a background of this risk factor combination.     

QT interval prolongation and the rate of malignant ventricular dysrhythmia and cardiac arrest in adult poisoned patients

IntroductionProlongation of QTc interval, a common electrocardiographic (ECG) abnormality encountered in the toxicology patient, is reportedly associated with an increased risk of malignant ventricular dysrhythmias (MVD), such as ventricular tachycardia (VT, with and without a pulse), ventricular fibrillation (VF), and/or cardiac arrest. Quantifiable cardiac arrest risk in relation to specific QTc interval length is not known in this population.MethodsWe conducted a retrospective, observational study to assess the rate of cardiac arrest and its association with degree of QTc prolongation in a cohort of patients requiring toxicology consultation.Results550 patients were included in our analysis (average age 36 years and 49% male). Average QTc was 453 milliseconds (ms). Overall incidence of cardiac arrest in the study cohort was 1.1% with 6 reported cases; when considering patients with QTc > 500 ms, incidence was 1.7%. Two patients with cardiac arrest experienced ventricular dysrhythmia with decompensation prior to cardiac arrest; four patients developed sudden cardiac arrest.ConclusionsThe risk of malignant ventricular dysrhythmia, including cardiac arrest, is low in this poisoned patient population with an overall rate of 1.1%. Two-thirds of cardiac arrest cases occurred in patients with normal QTc intervals. When considering patients with prolonged QTc intervals, the rate of cardiac arrest remains very low at 0.8%. Considering QTc greater than 500 ms, the rate of cardiac arrest is 1.7%. Further prospective studies are required to quantify the risk of malignant ventricular dysrhythmias, including cardiac arrest, and its relation to the degree of QTc interval in poisoned patients.     

A review of the investigational antiarrhythmic agent dronedarone

Arrhythmias are a major cause of morbidity and mortality, and atrial fibrillation is the most widespread disorder of cardiac rhythm. Amiodarone is an effective antiarrhythmic agent that has been in clinical use for about 20 years. It is effective for multiple types of arrhythmias, including atrial fibrillation, and has a low incidence of cardiac adverse events, including Torsade de Pointes. It has many noncardiac adverse effects that are serious and limit its long-term use. Dronedarone is an investigational antiarrhythmic agent that is designed to have similar cardiac effects to amiodarone but with fewer adverse effects. This review presents some of the animal and human studies that evaluate the effects of dronedarone.     

A wide, complex look at cardiac dysrhythmias

The diagnosis and treatment of cardiac dysrhythmias answers the following four questions: Is the patient stable? Is the rate fast or slow? Are the ventricular complexes wide or narrow? Is the rhythm regular or irregular? The most common narrow complex regular tachycardias are sinus tachycardia, atrial flutter, atrial tachycardia that blocks, and paroxysmal supraventricular tachycardia. Carotid sinus massage is useful in differentiation. Irregular narrow-complex tachycardias are usually atrial fibrillation. An ultra-rapid wide-complex or polymorphous irregular tachycardia is likely to be atrial fibrillation with ventricular preexcitation.

Wide-complex regular tachycardias present a special challenge, since wide beats may result from supraventricular or ventricular impulse formation. Ventricular tachycardia is more likely than supraventricular tachycardia in the presence of underlying ischemic heart disease, atrioventricular dissociation, fusion or capture beats, or a very broad (greater than .14 seconds) QRS complex. Still, misdiagnosis is common; the most costly mistake is over-diagnosis of SVT.

In emergencies, where vital organ hypoperfusion is present, the origin of the impulse and the name of the dysrhythmia are unimportant. With the exception of sinus tachycardia, all life-threatening, rapid tachycardias should be terminated by electrical cardioversion.     

Differentiation of Arrhythmias in the Dog by Measurement of Activation Sequence Using an Atrial and Two Ventricular Electrodes

Timing of atrioventricular activation and ventricular dispersion identifies and discriminates between beats of different origin. In eight dogs, three bipolar epicardial electrodes recorded left atrial and left and right ventricular depolarizations simultaneously during arrhythmias induced by programmed electrical stimulation and coronary artery occlusion and release. The interval between the left atrial and left ventricular intrinsic deflections (V₁-V₂) and between the left ventricular and right ventricular intrinsic deflections (V₁-V₂) of each heat was measured. Recordings were of normal sinus rhythm (NSR) (mean of five beats in 8/8 dogs), atrial flutter (AFL) (five beats of one episode), atrial fibrillation (AF) (144 beats in 29 episodes in 7/8), monomorphic ventricular tachycardia (MVT) (24 beats with six morphologies in 2/8), polymorphic ventricular tachycardia (PVT) (63 beats in 15 episodes in 5/8) and premature ventricular contractions (PVC) (29 beats with 29 morphologies in 5/8). Supraventricular rhythms can be differentiated from ventricular rhythms by V₁-V₂ timing. The mean difference in V₁-V₂ during AFL and AF vs NSR was 1 ms (range of 0–3 ms). The change from sinus during MVT ranged from 38 to 43 ms (m 31 ms) and during PVC 10 to 75 ms (m 38 ms). Thirty-five of 35 of these ectopic ventricular morphologies exhibited 10 ms or more timing difference compared to corresponding beats of NSR. PVT was consistently distinguished from supraventricular rhythms and MVT by the variability of V₁-V₂,A-V₁ intervals can be used to distinguish supraventricular arrhythmias from sinus rhythm; a 32 ms difference existed for AFL. AF could be detected by the variability in AV₁. One atrial and two ventricular leads can provide a means of differentiating normal sinus rhythm from supraventricular and ventricular arrhythmias that may be applicable to implantable antitachycardia devices.     

Is Dispersion of Ventricular Repolarization Rate Dependent?

QT dispersion has been adopted as a new index for the noninvasive assessment of the inhomogeneity of repolarization and has been evaluated in several clinical studies as an index of arrhythmia propensity. In most of these studies, indices of dispersion of repolarization were rate corrected by the Bazett formula calculating QT dispersion as QT_cmax-QT_cmin or JT dispersion as fT_cmax-fT_cmin, implying that dispersion of repolarization also changes with heart rate. This study aimed to determine in the electrically paced isolated heart whether dispersion of ventricular repolarization is rate dependent. Multiple (5–7) monophasic action potentials (MAPs) were recorded simultaneously from the epicardium and endocardium of both ventricles in 18 isolated Langendorff-perfused rabbit hearts. Hearts were paced from a right ventricular site at basic cycle lengths (CL) between 1,200 and 300 ms in 100-ms decrements. Action potential duration was measured at 90% repolarization (APD₉₀), and recovery time (RT) was defined as the sum of APD₉₀ and activation time in each of the simultaneous MAP recordings. The dispersion of APD₉₀ ond RT, respectively, were calculated as the maximal difference among all recordings. APD₉₀ and RT shortened continuously throughout the range of paced steady-state CLs from 1,200 to 300 ms. APD₉₀ was 197.6 ± 6.1 ms at a CL of 1,200 ms and decreased to 148.5 ± 2.5 ms at a CL of 300 ms (P < 0.0001). RT was 228.2 ± 6.2 ms at a CL of 1,000 ms and decreased to 175.9 ± 2.9 at a CL of 300 ms (P < 0.0001). In contrast, dispersion of APD₉₀ and RT did not change significantly. Dispersion of APD₉₀ was 24.8 ± 2.3 ms at a CL of 1,200 ms, 26.1 ± 1.9 msec at a CL of 1,000 ms, and 21.6 ± 2.1 at a CL of 300 ms (NS). Dispersion of RT was 29.7 ± 3.4 ms at a CL of 1,200 ms, 29.0 ± 3.0 ms at a CL of 1,000 ms, and 32.7 ± 3.2 ms at a CL of 300 ms (NS). In contrast to the duration of the QT interval, dispersion of ventricular repolarization does not change significantly with pacing induced changes in CL. Assuming that the rate-dependent behavior of action potential duration is similar between the rabbit and human heart, a rate correction of parameters of dispersion of repolarization is probably unnecessary.     

Ibutilide-induced long QT syndrome and torsade de pointes

Ibutilide is a class III antiarrhythmic agent used for the termination of atrial fibrillation and atrial flutter. It mainly affects membrane potassium currents and prolongs the cardiac action potential. This effect is reflected as QT interval prolongation on the surface electrocardiogram. Like other drugs that affect potassium currents, ibutilide is prone to induce a malignant ventricular tachycardia, torsade de pointes. We report four cases of torsade de pointes after administration of ibutilide for pharmacologic cardioversion of atrial fibrillation and atrial flutter; three of these cases required direct current cardioversion for termination of torsade de pointes. All four patients were female. We discuss the risk factors for development of ibutilide-induced torsade de pointes.     

Promotion of Ventricular Tachycardia Induction by Procainamide in Dogs with Inducible Ventricular Fibrillation Late After Myocardial Infarction

The influence of procainamide on inducible ventricular tachyarrhythmias was evaluated in 35 dogs with experimental myocardial infarction, and 9 normal dogs. Programmed stimulation was performed from the right ventricular apex via a percutaneously positioned electrode catheter, using up to five extrastimuli before and after intravenous administration of procainamide (15 mg/kg). Procainamide levels in postinfarct dogs were 8.5 +/- 0.7 micrograms/mL (range 5.3-13.6 micrograms/mL). Procainamide exerted its greatest effect in postinfarct dogs with reproducible baseline ventricular fibrillation. Six of nine dogs (P less than 0.05) with ventricular fibrillation had sustained monomorphic ventricular tachycardia (cycle length: 147 +/- 4 msec) induced after procainamide administration. This ventricular tachycardia required significantly more extrastimuli than baseline ventricular fibrillation (3 +/- 0.3 extrastimuli before vs 4 +/- 0.3 extrastimuli after procainamide). Procainamide never converted ventricular fibrillation to ventricular tachycardia in normal dogs. Procainamide had minimal effect on inducible ventricular tachycardia after myocardial infarction. Ventricular tachycardia induction was abolished in only 2 of 17 dogs despite significant prolongation of electrophysiological parameters. Ventricular tachycardia cycle length, and the number of extrastimuli required were unchanged by procainamide in this subgroup. Conclusion: Ventricular tachycardia is insensitive to the antiarrhythmic properties of procainamide in this model. In contrast, procainamide is able to convert postinfarction ventricular fibrillation to ventricular tachycardia, presumably by promoting sustained, organized reentry. This previously undescribed action is an unusual form of proarrhythmic effect, and suggests that this drug should be used cautiously in patients after myocardial infarction.     

Congenital long QT syndromes: clinical features, molecular genetics and genetic testing

Congenital long QT syndrome (LQTS) is a primary electrical disease characterized by a prolonged QT interval in the surface electrocardiogram and increased predisposition to a typical polymorphic ventricular tachycardia, termed Torsade de Pointes. Most patients with LQTS are asymptomatic and are diagnosed incidentally based on an electrocardiogram. Symptomatic patients may suffer from severe cardiac events, such as syncope and/or sudden cardiac death. Autosomal dominant forms are caused by heterozygous mutations in genes encoding the components of the ion channels. The autosomal recessive form with congenital deafness is also known as Jervell and Lang-Nielsen syndrome. It is caused by homozygous mutations or certain compound heterozygous mutations. Depending on the genetic defects, there are differences in the age of onset, severity of symptoms, and number of cardiac events and event triggers. With advances in gene technology, it is now feasible to perform genetic testing for LQTS, especially for those with family history. Identification of the mutation will lead to better management of symptoms and more targeted treatment, depending on the underlying genetic defect, resulting in a reduction of mortality and cardiac events.