Sudden cardiac death and polymorphous ventricular tachycardia in patients with normal QT intervals and normal systolic cardiac function

Personalized medicine in the dish to prevent calcium leak associated with short-coupled polymorphic ventricular tachycardia in patient-derived cardiomyocytes

BACKGROUND

Polymorphic ventricular tachycardia (PMVT) is a rare genetic disease associated with structurally normal hearts which in 8% of cases can lead to sudden cardiac death, typically exercise-induced. We previously showed a link between the RyR2-H29D mutation and a clinical phenotype of short-coupled PMVT at rest using patient-specific hiPSC-derived cardiomyocytes (hiPSC-CMs). In the present study, we evaluated the effects of clinical and experimental anti-arrhythmic drugs on the intracellular Ca2+ handling, contractile and molecular properties in PMVT hiPSC-CMs in order to model a personalized medicine approach in vitro.

METHODS

Previously, a blood sample from a patient carrying the RyR2-H29D mutation was collected and reprogrammed into several clones of RyR2-H29D hiPSCs, and in addition we generated an isogenic control by reverting the RyR2-H29D mutation using CRIPSR/Cas9 technology. Here, we tested 4 drugs with anti-arrhythmic properties: propranolol, verapamil, flecainide, and the Rycal S107. We performed fluorescence confocal microscopy, video-image-based analyses and biochemical analyses to investigate the impact of these drugs on the functional and molecular features of the PMVT RyR2-H29D hiPSC-CMs.

RESULTS

The voltage-dependent Ca2+ channel inhibitor verapamil did not prevent the aberrant release of sarcoplasmic reticulum (SR) Ca2+ in the RyR2-H29D hiPSC-CMs, whereas it was prevented by S107, flecainide or propranolol. Cardiac tissue comprised of RyR2-H29D hiPSC-CMs exhibited aberrant contractile properties that were largely prevented by S107, flecainide and propranolol. These 3 drugs also recovered synchronous contraction in RyR2-H29D cardiac tissue, while verapamil did not. At the biochemical level, S107 was the only drug able to restore calstabin2 binding to RyR2 as observed in the isogenic control.

CONCLUSIONS

By testing 4 drugs on patient-specific PMVT hiPSC-CMs, we concluded that S107 and flecainide are the most potent molecules in terms of preventing the abnormal SR Ca2+ release and contractile properties in RyR2-H29D hiPSC-CMs, whereas the effect of propranolol is partial, and verapamil appears ineffective. In contrast with the 3 other drugs, S107 was able to prevent a major post-translational modification of RyR2-H29D mutant channels, the loss of calstabin2 binding to RyR2. Using patient-specific hiPSC and CRISPR/Cas9 technologies, we showed that S107 is the most efficient in vitro candidate for treating the short-coupled PMVT at rest.

A SPRY1 domain cardiac ryanodine receptor variant associated with short-coupled torsade de pointes

Idiopathic ventricular fibrillation (IVF) causes sudden death in young adult patients without structural or ischemic heart disease. Most IVF cases are sporadic and some patients present with short-coupled torsade de pointes, the genetics of which are poorly understood. A man who had a first syncope at the age of 35 presented with frequent short-coupled premature ventricular beats with bursts of polymorphic ventricular tachycardia and then died suddenly. By exome sequencing, we identified three rare variants: p.I784F in the SPRY1 of the ryanodine receptor 2 (RyR2), p.A96S in connexin 40 (Cx40), reported to affect electrical coupling and cardiac conduction, and a nonsense p.R244X in the cardiac-specific troponin I-interacting kinase (TNNI3K). We assessed intracellular Ca2+ handling in WT and mutant human RYR2 transfected HEK293 cells by fluorescent microscopy and an enhanced store overload-induced Ca2+ release in response to cytosolic Ca2+ was observed in RyR2-I784F cells. In addition, crystal structures and thermal melting temperatures revealed a conformational change in the I784F-SPRY1 domain compared to the WT-domain. The novel RyR2-I784F variant in SPRY1 domain causes a leaky channel under non-stress conditions. The presence of several variants affecting Ca2+ handling and cardiac conduction suggests a possible oligogenic origin for the ectopies originating from Purkinje fibres.

Short coupled torsade de pointes: Critical timing of the ventricular premature beats

In this case report, we describe a 73 year old female with structuraly normal heart that developed shortcoupled torsades de pointes (TdP) resulting in an electrical storm unresponsible to several antiarrhythmic drugs, but fully controlled with verapamil. The critical timing of the ventricular premature beats that initiated TdP corresponded to those that occurred at the peak of the previous T wave. This behavior differentiates this entity from other forms of malignant ventricular arrhythmias in patients with structurally normal heart. It is imperative that the clinical set-up and unique electrocardiographic fingerprint of this unusual malignant entity be assiduously recognized since verapamil can be life-saving in this condition.

Polymorphic Ventricular Tachycardia with a Normal QTc Interval in a Patient with COVID-19 and Fever: Case Report

Arrhythmias or conduction system disease are not the most common manifestation of COVID-19 infection in patients requiring hospital admission. Torsade de pointes typically occurs in bursts of self-limiting episodes with symptoms of dizziness and syncope. However, it may occasionally progress to ventricular fibrillation and sudden death. In this article, we report a case of COVID-19 patient who developed polymorphic ventricular tachycardia with torsade de pointes morphology with normal QTc interval in the setting of fever. An 81-year-old woman was admitted with symptoms of COVID-19. She was treated with hydroxychloroquine, azithromycin, and doxycycline at an outside facility and finished the treatment 5 days prior to admission to our facility. Her course was complicated by atrial fibrillation with rapid ventricular response requiring cardioversion. Later, she developed two episodes of polymorphic ventricular tachycardia with TdP morphology with normal QTc. There was a correlation with fever triggering the ventricular tachycardia. We advocated aggressive fever control given the QTc was normal and stable. Following fever control, the patient remained stable and had no abnormal rhythm. COVID-19 patients are prone to different arrhythmias including life-threatening ventricular arrhythmias with normal left ventricular systolic function and normal QTc, and they should be monitored for fever and electrolyte abnormality during their hospital stay.

Transgenic Rabbit Models in Proarrhythmia Research

Drug-induced proarrhythmia constitutes a potentially lethal side effect of various drugs. Most often, this proarrhythmia is mechanistically linked to the drug's potential to interact with repolarizing cardiac ion channels causing a prolongation of the QT interval in the ECG. Despite sophisticated screening approaches during drug development, reliable prediction of proarrhythmia remains very challenging. Although drug-induced long-QT-related proarrhythmia is often favored by conditions or diseases that impair the individual's repolarization reserve, most cellular, tissue, and whole animal model systems used for drug safety screening are based on normal, healthy models. In recent years, several transgenic rabbit models for different types of long QT syndromes (LQTS) with differences in the extent of impairment in repolarization reserve have been generated. These might be useful for screening/prediction of a drug's potential for long-QT-related proarrhythmia, particularly as different repolarizing cardiac ion channels are impaired in the different models. In this review, we summarize the electrophysiological characteristics of the available transgenic LQTS rabbit models, and the pharmacological proof-of-principle studies that have been performed with these models—highlighting the advantages and disadvantages of LQTS models for proarrhythmia research. In the end, we give an outlook on potential future directions and novel models.

Hypokalemia unmasking underlying premature ventricular contraction induced polymorphic ventricular tachycardia: Low potassium is not always the culprit!

Hypokalemia is prevalent in patients resuscitated from out-of-hospital cardiac arrest and can contribute to polymorphic ventricular tachycardia (PMVT) by prolonging the QT interval. We present an interesting scenario of malignant ventricular arrythmia initially attributed to moderate hypokalemia that persisted after correction of potassium. Subsequent electrophysiological study showed two frequent PMVT-triggering PVCs mapped to the base of the antero-lateral papillary muscle and the para-Hisian region of the right side of the interventricular septum. The patient underwent catheter ablation to prevent further recurrences and dual chamber ICD implantation for secondary prevention.

Idiopathic short-coupled ventricular tachyarrhythmias: Systematic review and validation of electrocardiographic indices

INTRODUCTION

Idiopathic short-coupled ventricular tachyarrhythmias make up a considerable proportion of ventricular tachyarrhythmias in structurally normal hearts and are the cause of 5-10% of unexpected sudden cardiac deaths. There is disparity in the literature regarding their description and a lack of formal diagnostic criteria to define them.

OBJECTIVE

To validate ECG indices for the diagnosis of these ventricular tachyarrythmias and to subsequently unify their differing descriptions in the literature under a new terminology: Idiopathic Short-Coupled Ventricular Tachyarrhythmias.

METHODS

We conducted a systematic review of all published studies describing short-coupled torsades de pointes, idiopathic ventricular fibrillation and polymorphic ventricular tachycardia. Published tracings were analysed using a standard set of criteria to define the different ECG intervals. Previously proposed diagnostic indices were validated using a control group of previously published long-coupled torsades de pointes cases.

RESULTS

Validation of the ECG indices revealed that a coupling interval < 400 ms was the most reliable measurement (sensitivity 100%, specificity 97%), followed by a coupling interval/QT < 1 (sensitivity 96%, specificity 100%).

CONCLUSION

Idiopathic short-coupled ventricular tachyarrhythmias encompass all previous descriptions of this tachyarrhythmia including idiopathic ventricular fibrillation, short-coupled torsades de pointes, Purkinje-related torsades de pointes and idiopathic polymorphic ventricular tachycardia. This arrhythmia can be diagnosed by newly proposed criteria with high sensitivity and specificity.

The congenital long QT syndrome Type 3: An update

Congenital long QT syndrome type 3 (LQT3) is the third in frequency compared to the 15 forms known currently of congenital long QT syndrome (LQTS). Cardiac events are less frequent in LQT3 when compared with LQT1 and LQT2, but more likely to be lethal; the likelihood of dying during a cardiac event is 20% in families with an LQT3 mutation and 4% with either an LQT1 or an LQT2 mutation. LQT3 is consequence of mutation of gene SCN5A which codes for the Nav1.5 Na+ channel α-subunit and electrocardiographically characterized by a tendency to bradycardia related to age, prolonged QT/QTc interval (mean QTc value 478 ± 52 ms), accentuated QT dispersion consequence of prolonged ST segment, late onset of T wave and frequent prominent U wave because of longer repolarization of the M cell across left ventricular wall.

Coronary spasm during cardiac electrophysiological study following isoproterenol infusion

Sudden cardiac death (SCD) remains the leading cause of death in industrialized world. The majority of SCD is caused by ventricular fibrillation associated with structural and/or ischemic heart disease. Ventricular fibrillation represents the final common pathway for SCD and, thus, is an attractive target for ablation. According to class I recommendation level of evidence A, an implantable cardioverter defibrillator (ICD) should be implanted for such patients [1]. Other than programmed electrical extrastimulus technique, isoproterenol infusion is commonly used in invasive cardiac electrophysiology labs for arrhythmia induction. We hereby report a rare case of transient coronary spasm during isoproterenol infusion for ventricular tachycardia induction testing.

Prinzmetal angina: ECG changes and clinical considerations: a consensus paper

BACKGROUND

We will focus our attention in this article in the ECG changes of classical Prinzmetal angina that occur during occlusive proximal coronary spasm usually in patients with normal or noncritical coronary stenosis.

RESULTS

The most important ECG change during a focal proximal coronary spasm is in around 50% of cases the appearance of peaked and symmetrical T wave that is followed, if the spasm persist, by progressive ST-segment elevation that last for a few minutes, and later progressively resolve. The most frequent ECG changes associated with ST-segment elevation are: (a) increased height of the R wave, (b) coincident S-wave diminution, (c) upsloping TQ in many cases, and (d) alternans of the elevated ST-segment and negative T wave deepness in 20% of cases. The presence of arrhythmias is very frequent during Prinzmetal angina crises, especially ventricular arrhythmias. The prevalence and importance of ventricular arrhythmias were related to: (a) duration of episodes, (b) degree of ST-segment elevation, (c) presence of ST-T wave alternans, and (d) the presence of >25% increase of the R wave.

CONCLUSIONS

The incidence of Prinzmetal angina is much lower then 50 years ago for many reasons including treatment with calcium channel blocks to treat hypertension and ischemia heart disease and the decrease of smoking habits.

In vivo human left-to-right ventricular differences in rate adaptation transiently increase pro-arrhythmic risk following rate acceleration

Left-to-right ventricular (LV/RV) differences in repolarization have been implicated in lethal arrhythmias in animal models. Our goal is to quantify LV/RV differences in action potential duration (APD) and APD rate adaptation and their contribution to arrhythmogenic substrates in the in vivo human heart using combined in vivo and in silico studies. Electrograms were acquired from 10 LV and 10 RV endocardial sites in 15 patients with normal ventricles. APD and APD adaptation were measured during an increase in heart rate. Analysis of in vivo electrograms revealed longer APD in LV than RV (207.8 ± 21.5 vs 196.7 ± 20.1 ms; P<0.05), and slower APD adaptation in LV than RV (time constant τ(s) =47.0 ± 14.3 vs 35.6 ± 6.5 s; P<0.05). Following rate acceleration, LV/RV APD dispersion experienced an increase of up to 91% in 12 patients, showing a strong correlation (r(2) =0.90) with both initial dispersion and LV/RV difference in slow adaptation. Pro-arrhythmic implications of measured LV/RV functional differences were studied using in silico simulations. Results show that LV/RV APD and APD adaptation heterogeneities promote unidirectional block following rate acceleration, albeit being insufficient for establishment of reentry in normal hearts. However, in the presence of an ischemic region at the LV/RV junction, LV/RV heterogeneity in APD and APD rate adaptation promotes reentrant activity and its degeneration into fibrillatory activity. Our results suggest that LV/RV heterogeneities in APD adaptation cause a transient increase in APD dispersion in the human ventricles following rate acceleration, which promotes unidirectional block and wave-break at the LV/RV junction, and may potentiate the arrhythmogenic substrate, particularly in patients with ischemic heart disease.

Spontaneous deterioration of atrioventricular nodal reentrant tachycardia to polymorphic ventricular tachycardia in the absence of heart disease

Atrioventricular nodal reentrant tachycardia (AVNRT) is usually associated with a good prognosis. This is a case of a 57-year woman who presented with supraventricular tachycardia that spontaneously deteriorated to polymorphic ventricular tachycardia (PVT). The PVT terminated without treatment after 16 seconds. Extensive cardiac evaluation including echocardiography, stress testing, coronary angiography, and cardiac magnetic resonance imaging did not reveal any structural heart disease. Electrophysiology testing demonstrated typical AVNRT which was successfully treated with cryoablation. The clinical ventricular tachycardia could not be reproduced despite the use of an aggressive induction protocol and isoproterenol. Postablation, exercise treadmill testing did not provoke any tachyarrhythmia. The patient is doing well 13 months later. In summary, we present the rare finding of a moderately fast, typical AVNRT degenerating to a long run of PVT, in the absence of any detectable heart disease or other etiology for PVT.

Short-coupled variant of torsade de pointes

A 36-year-old man with a history of primary sclerosing cholangitis and epilepsy was admitted to our hospital for cholangitis. During admission he was resuscitated because of ventricular fibrillation. ECGs showed multiple ventricular premature beats (VPBs) with a short coupling interval (240 ms), resulting in frequent torsade de pointes (TdP). In total, the patient had to be defibrillated 12 times. Short-coupled TdP is a rare variant of polymorphic ventricular tachycardia, with unknown aetiology. Verapamil seems to be the only drug able to suppress the arrhythmia. Verapamil, however, does not lower the risk of sudden death; therefore, an ICD implantation is advised. (Neth Heart J 2008;16:246-9.).

Exercise-induced polymorphic ventricular tachycardia in adults without structural heart disease

Patients with catecholaminergic polymorphic ventricular tachycardia present at a young age with exercise-induced ventricular arrhythmias (VAs) and may have a positive family history. We describe 8 patients who presented with exercise-induced symptoms as adults, have a negative family history, and responded to beta-blocker therapy. The study evaluated exercise treadmill electrocardiographic data from patients referred for exercise-induced VA. Inclusion criteria consisted of development of bidirectional, pleomorphic, or polymorphic ventricular tachycardia with exercise, adult age at first onset, negative family history, and no evidence of structural heart disease. We correlated VA configurations with respect to heart rate before and after beta-blocker therapy. Patients displayed a pattern of increasing ventricular complexity with increasing heart rate. The appropriate beta blocker (n = 7) or calcium channel blocker (n = 1) was defined as the dose that resulted in control of symptoms. Three patients showed suppression of VA with sinus tachycardia at peak heart rate. Six patients had decreased VA defined as absence of higher complexity arrhythmias. With drug therapy, average heart rate associated with premature ventricular complex couplets/triplets increased, whereas duration and complexity of premature ventricular complexes decreased. One patient had an automatic implantable cardiac defibrillator placed but has had no discharges from the device since starting the appropriate beta blocker. In conclusion, these patients appear to respond well to beta-blocker or calcium channel blocker therapy with decreased ectopic complexity and an increased heart rate threshold for inducing VA.

Association of atrial arrhythmia and sinus node dysfunction in patients with catecholaminergic polymorphic ventricular tachycardia

BACKGROUND

This study was performed to investigate the frequency and importance of supraventricular arrhythmia and sinus node (SN) dysfunction in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT).

METHODS AND RESULTS

Eight patients with CPVT (mean age: 16.8+/-8.1 years) underwent an electrophysiological study. SN recovery time (1,389+/-394 ms) was slightly prolonged, and 4 of 8 patients had abnormal values. Atrial flutter (AF) was induced by low-rate atrial pacing in 2 patients and by isoproterenol infusion in 1 patient. Atrial fibrillation (Af) was induced by isoproterenol infusion in 2 patients. One patient presented with Af during the follow-up period, and 2 of 4 patients with AF/Af presented with increased SN recovery time.

CONCLUSIONS

Patients with CPVT frequently have associated with SN dysfunction, and inducible atrial tachyarrhythmias, which indicate that the pathogenesis of CPVT is limited not only to the ventricular myocardium, but also to broad regions of the heart, including the SN and atrial muscle.

A Novel Early Onset Lethal Form of Catecholaminergic Polymorphic Ventricular Tachycardia Maps to Chromosome 7p14-p22

INTRODUCTION

Previously, autosomal dominant catecholaminergic polymorphic ventricular tachycardia (CPVT [1]) was mapped to chromosome 1q42-43 with identification of pathogenic mutations in RYR2. Autosomal recessive CPVT (2) was mapped to chromosome 1p13-21, leading to the identification of mutations in CASQ2. In this study, we aimed to elucidate clinical phenotypes of a new variant of CPVT (3) in an inbred Arab family and also delineate the chromosomal location of the gene causing CPVT (3).

METHODS AND RESULTS

In a highly inbred family, clinical symptoms of CPVT appeared early in childhood (7-12 years) and in three of the four cases, the first appearance of symptoms turned into a fatal outcome. Parents of the affected children were first-degree cousins and without any symptoms. Segregation analysis suggested an autosomal recessive inheritance. A genome-wide search using polymorphic DNA markers mapped the disease locus to a 25-Mb interval on chromosome 7p14-p22. A maximal multipoint LOD score of 3.17 was obtained at marker D7S493. Sequencing of putative candidate genes, SP4, NPY, FKBP9, FKBP14, PDE1C, and TBX20, in and around this locus, did not reveal any mutation.

CONCLUSIONS

We have identified a novel highly malignant autosomal recessive form of CPVT and mapped this disorder to a 25-Mb interval on chromosome 7p14-p22.

Idiopathic polymorphic ventricular tachycardia with normal QT interval in a structurally normal heart

Polymorphic ventricular tachycardia (PVT) is a life-threatening arrhythmia that is typically related to long QT syndrome, organic heart disease, electrolyte abnormalities, cardiotoxic drugs, or adrenergic stimulation. A review of the literature reveals that PVT with normal QT interval and without underlying cause is quite rare. We report a case of idiopathic spontaneous PVT with structurally normal heart and without electrolyte abnormalities, drug reactions, or evidence of catecholamine induced arrhythmia. We also review the literature on the electrocardiographic characteristics and management of idiopathic PVT.

Refining detection of drug-induced proarrhythmia: QT interval and TRIaD

QT interval prolongation is so frequently associated with torsades de pointes (TdP) that it has come to be recognized as a surrogate marker of this unique tachyarrhythmia. However, not only does TdP not always follow QT interval prolongation, but TdP can occur even in the absence of a prolonged QT interval. Worse still, even shortening of the QT interval may be associated with serious arrhythmias (particularly ventricular tachycardia [VT] and ventricular fibrillation [VF]). It appears increasingly probable that the distinction between various ventricular tachyarrhythmias may be arbitrary, and drug-induced TdP, polymorphic VT, VT, catecholaminergic polymorphic VT, and VF may represent discrete entities within a spectrum of drug-induced proarrhythmia. Although they are differentiated by the coupling interval and the duration of QT interval, they appear to share a common substrate: a set of disturbances of repolarization characterized by Triangulation, Reverse use dependency, electrical Instability of the action potential, and Dispersion (TRIaD). It is becoming increasingly evident that augmentation of TRIaD, rather than changes in the duration of QT interval, provides the proarrhythmic substrate. In contrast, when not associated with an increase of TRIaD, QT interval prolongation can be an antiarrhythmic property. Electrophysiologically, augmentation of TRIaD can be explained by inhibition of hERG (human ether-a-go-go related gene) channel. Because drug-induced disturbances in repolarization commonly result from inhibition of hERG channels or I(Kr), hERG blockade and the resulting prolongation of QT interval are important properties of a drug to be studied. However, these need only be a concern if associated with TRIaD. More significantly, TRIaD so often precedes prolongation of action potential duration or QT interval and ventricular tachyarrhythmias that it should be considered a marker of proarrhythmia until proven otherwise, even in the absence of QT interval prolongation. Detecting drug-induced augmentation of TRIaD may offer an additional, more sensitive, and accurate indicator of the broader proarrhythmic potential of a drug than may QT interval prolongation alone.

Drug-induced QT dispersion: does it predict the risk of torsade de pointes?

Drug-induced delay in ventricular repolarization and proarrhythmias have attracted considerable regulatory attention. The measure of delayed ventricular repolarization most frequently used clinically is the ability of the new chemical entity (NCE) to prolong the QTc interval on surface electrocardiogram. Before they can be approved, new chemical entities with systemic bioavailability require characterization for their potential to prolong the QTc interval. Inevitably, QTc interval prolongation has come to be recognized as a surrogate marker of the risk of torsade de pointes (TdP)--a unique form of potentially fatal polymorphic ventricular tachycardia. Although it is the best and the simplest clinical measure that is available at present, QTc interval is not a reliable surrogate of TdP. Intramyocardial dispersion of repolarization appears to play a more important role both in electrical stability of the ventricles and in arrhythmogenesis. The potential importance of myocardial dispersion of refractoriness in arrhythmogenesis has led to a number of attempts to assess it from the surface electrocardiogram. This review summarizes the evidence for and against the predictive value of one of these attempts-measurement of the so-called QT dispersion. Although the concept of QT dispersion is the best known and most widely investigated, it has also proved to be the least successful in predicting the risks of drug-induced TdP.

Catecholaminergic polymorphic ventricular tachycardia: successful emergency treatment with intravenous propranolol

Catecholaminergic polymorphic ventricular tachycardia (VT) is a rare arrhythmogenic disorder, which may cause sudden death and whose relationships with mutations in cardiac ryanodine receptor gene have been recently established. The present article reports a catecholaminergic polymorphic VT case of a 9-year-old girl, without any previous history of syncope, who has been found unconscious while playing and referred comatose to pediatric intensive care unit. The electrocardiogram pattern showed runs of bidirectional and polymorphic VT degenerating into ventricular fibrillation, without QT interval abnormalities. Various attempts of cardioversion, lidocaine, and magnesium sulfate intravenous infusions were only partially effective. Owing to catecholaminergic polymorphic VT highly suggesting electrocardiogram pattern, intravenous propranolol was administered, achieving immediate VT interruption. Long-term nadolol therapy effectively prevented further arrhythmias, with no relapses up to 10 months later; a good neurologic recovery was also obtained. Genetic evaluation revealed in this patient-but not in relatives-a mutation in ryanodine receptor gene on chromosome 1.

A missense mutation in CASQ2 is associated with autosomal recessive catecholamine-induced polymorphic ventricular tachycardia in Bedouin families from Israel

Catecholamine-induced polymorphic ventricular tachycardia (CPVT) is characterized by episodes of syncope, seizures or sudden death, in response to physical activity or emotional stress, and affects mainly young children with morphologically normal hearts. We have recently described an autosomal recessive form of the disorder in seven families from a Bedouin tribe in the north of Israel, and mapped the disease-causing gene to chromosome 1p13-1p21. Direct sequencing of the calsequestrin 2 (CASQ2), a candidate gene from within the linkage interval, revealed a negatively charged aspartic acid change to a positively charged histidine at position 307 of the protein. CASQ2 serves as the major calcium reservoir within cardiac myocytes. This mutation occurs in a highly conserved residue of the protein. The implication of the calcium release cascade in this disease, may lead to a better understanding of the pathophysiologic events underlying ventricular tachycardia, and to the use of drugs directly involved in intracellular calcium control for the treatment of the CPVT patients.

Catecholaminergic polymorphic ventricular tachycardia: electrocardiographic characteristics and optimal therapeutic strategies to prevent sudden death

OBJECTIVE

To investigate the clinical outcome, ECG characteristics, and optimal treatment of catecholaminergic polymorphic ventricular tachycardia (CPVT), a malignant and rare ventricular tachycardia.

PATIENTS AND METHODS

Questionnaire responses and ECGs of 29 patients with CPVT were evaluated. Mean (SD) age of onset was 10.3 (6.1) years.

RESULTS

The initial CPVT manifestations were syncope (79%), cardiac arrest (7%), and a family history (14%). ECGs showed sinus bradycardia and a normal QTc. Mean heart rate during CPVT was 192 (30) beats/min. Most cases were non-sustained (72%), but 21% were sustained and 7% were associated with ventricular fibrillation. The morphology of CPVT was polymorphic (62%), polymorphic and bidirectional (21%), bidirectional (10%), or polymorphic with ventricular fibrillation (7%). There was 100% inducement of CPVT by exercise, 75% by catecholamine infusion, and none by programmed stimulation. No late potential was recorded. Onset was in the right ventricular outflow tract in more than half the cases. During a follow up of 6.8 (4.9) years, sudden death occurred in 24% of the patients, 7% of whom had anoxic brain damage. Autosomal dominant inheritance was seen in 8% of the patients' families. beta Blockers completely controlled CPVT in only 31% of cases. Calcium antagonists partially suppressed CPVT in autosomal dominant cases.

CONCLUSIONS

CPVT may arise in certain distinct areas but the prognosis is poor. The onset of CPVT may be an indication for an implanted cardioverter-defibrillator.

Anesthesia for a patient with catecholaminergic polymorphic ventricular tachycardia

IMPLICATIONS

A patient with catecholaminergic polymorphic ventricular tachycardia required anesthesia for implantation of a defibrillator. The diagnostic criteria, treatment, and anesthetic considerations for this rare, familial dysrhythmia are described.

Exercise-induced bidirectional ventricular tachycardia with alternating right and left bundle branch block-type patterns--a case report

Exercise-induced ventricular tachycardia in young adults may occur with various structural heart diseases or with structurally normal heart. The structural heart diseases reported to cause exercise-induced ventricular tachycardia in this patient population include arrhythmogenic right ventricular dysplasia, hypertrophic cardiomyopathy, dilated cardiomyopathy, myocarditis, congenital heart disease, and myocardial ischemia. The conditions well identified to cause exercise-induced ventricular tachycardia with structurally normal heart are congenital long-QT syndrome and familial polymorphic ventricular tachycardia. Exercise-induced ventricular tachycardia may display polymorphic, monomorphic, or bidirectional morphologies. A case of exercise-induced catecholamine-sensitive bidirectional ventricular tachycardia with alternating right and left bundle branch block patterns is reported in a young boy in the absence of structural heart disease, the conditions causing bidirectional ventricular tachycardia, and family history of such an event or sudden cardiac death. The bidirectional tachycardia typically displays right bundle branch block in right precordial leads with alternating polarity of the QRS-complex in frontal plane leads but in this case the bidirectional morphology of tachycardia was caused by alternating right and left bundle branch block-type patterns. The conditions causing bidirectional ventricular tachycardia are digoxin toxicity, ischemic heart disease, hypokalemia, myocarditis, and familial polymorphic ventricular tachycardia syndrome but the exact cause in this patient remained obscure, and the possibility of an underlying electrical or ion channel disease of the heart could not be ruled out.

Mapping and ablation of idiopathic ventricular fibrillation

BACKGROUND

Ventricular fibrillation is the main mechanism of sudden cardiac death. The feasibility of eliminating recurrent episodes by catheter ablation has not been reported.

METHODS AND RESULTS

Twenty-seven patients without known heart disease (13 men, 14 women, 41+/-14 years of age) were studied after being resuscitated from recurrent (10+/-12) episodes of primary idiopathic ventricular fibrillation; 23 had received a defibrillator. The first initiating beat of ventricular fibrillation had an identical electrocardiographic morphology and coupling interval (297+/-41 ms) to preceding isolated premature beats typically noted in the aftermath of resuscitation. These triggers were localized by mapping the earliest electrical activity and ablated by local radiofrequency delivery. Outcome was assessed by Holter and defibrillator memory interrogation. Premature beats were elicited from the Purkinje conducting system in 23 patients: from the left ventricular septum in 10, from the anterior right ventricle in 9, and from both in 4. The interval from the Purkinje potential to the following myocardial activation varied from 10 to 150 ms during premature beat but was 11+/-5 ms during sinus rhythm, indicating location at peripheral Purkinje arborization. The premature beats originated from the right ventricular outflow tract muscle in 4 patients. The accuracy of mapping was confirmed by acute elimination of premature beats during local radiofrequency delivery. During a follow-up of 24+/-28 months, 24 patients (89%) had no recurrence of ventricular fibrillation without drug.

CONCLUSIONS

Primary idiopathic ventricular fibrillation is a syndrome characterized by dominant triggers from the distal Purkinje system. These sources can be eliminated by focal energy delivery.

The anaesthetic management of a parturient with polymorphic catecholamine-sensitive ventricular tachycardia

Polymorphic catecholamine-sensitive ventricular tachycardia is an uncommon but potentially life-threatening condition. There are few reports of this condition in pregnancy. It is one of five types of polymorphic ventricular arrhythmia, the others being long-QT syndrome, short coupled variant of torsade de point malignant disease, idiopathic ventricular fibrillation with normal ECG and Brugada syndrome. Exercise and stress can precipitate ventricular tachyarrhythmias in patients with polymorphic catecholamine-sensitive ventricular tachycardia and it is important to avoid increases in plasma catecholamine levels. We report on the anaesthetic management of a parturient with this condition, for elective caesarean section and discuss the stress response in parturients receiving regional and general anaesthesia.

Torsade de pointes with a normal QT interval associated with hypokalemia: a case report

The patient was a 46-year-old man with a history of syncope attack after diarrhea. Nonsustained polymorphic ventricular tachycardia (PVT) initiated by short-coupled premature ventricular complex was detected by Holter monitoring. No organic heart disease was found, and the QT interval during sinus rhythm was normal. It was thought that the PVT might be related to hypokalemia, so electrophysiological studies were performed under the condition of hypokalemia (K=3.4mmol/L), after potassium loading (K=4.2mmol/L) and after oral amiodarone therapy. Under the condition of hypokalemia, nonsustained PVT occurred spontaneously, and the monophasic action potential duration at 90% repolarization (MAPD90) at the right ventricular apex was very short (175 ms). The MAPD90 returned to normal after loading potassium (230ms) and after oral amiodarone therapy (240ms), and PVT no longer occurred. With continued oral amiodarone and spironolactone therapy, the patient has been free of syncope attack over a follow-up period of 5 years.

Aborted sudden cardiac death: a clinical perspective

Sudden cardiac death in the community remains a major public health problem. The purpose of this article is to outline the epidemiology, pathophysiology, and immediate treatment of the cardiac arrest victim. The subsequent in-hospital diagnostic evaluation and management will then be discussed with an emphasis on the role of the implantable cardioverter-defibrillator. A systematic and evidence based approach should help to optimize patient care.

Polymorphic ventricular tachycardia in patients with vasospastic angina--clinical and electrocardiographic characteristics and long-term outcome

There have been few clinical studies exploring the characteristics of spontaneous polymorphic ventricular tachycardia (VT) during a vasospastic angina attack. During a 4-year recruitment period, Holter ECG recordings were monitored for 42+/-24 h during a drug-free period in 60 consecutive patients with vasospastic angina (VSA) and of these, 8 patients had at least one episode of polymorphic VT during monitoring. Ischemic ST segment elevation was immediately preceded the spontaneous polymorphic VT in all 8 patients, 4 of whom had silent coronary vasospasm. Immediately before the onset of polymorphic VT, both R-on-T and long-short sequences were observed in 4 of the 8 patients and ST wave alternans were recorded in 2 patients. VT exhibited a pattern of torsade de pointes in 4 of the 8 patients. Five patients underwent electrophysiologic testing during a drug-free asymptomatic phase, and polymorphic VT was induced in 2 of the 5 patients, with one developing ventricular fibrillation. During a follow-up period of 73+/-17 months, there was a significant difference in the incidence of sudden death between patients with and without VT (2/8 cases [25%] vs 0/52 [0%]; p<0.01). Thus, vasospastic attacks, even if asymptomatic, that immediately precede the development of polymorphic VT may be associated with a repolarization abnormality and an increased risk of sudden death.

Pause-dependent polymorphic ventricular tachycardia during long-term treatment with dofetilide: a placebo-controlled, implantable cardioverter-defibrillator-based evaluation

OBJECTIVES

To compare the incidence of pause-dependent polymorphic ventricular tachycardia (PVT) in patients with implantable cardioverter-defibrillators (ICDs) randomly assigned to the QT-prolonging antiarrhythmic dofetilide or placebo.

BACKGROUND

Drug-related torsade de pointes (TdP) is usually recognized within days of initiating therapy, but its incidence during long-term therapy is unknown.

METHODS

We assessed the frequency of TdP and ICD electrograms compatible with TdP in a multicenter study that randomized ICD patients to placebo (n = 87) or dofetilide (n = 87). As reported elsewhere, the number of patients with a primary trial end point (ICD intervention for VT or ventricular fibrillation) was similar in the two groups. For this analysis, a qualifying event was TdP (on electrocardiogram) or an intracardiac electrogram showing pause-dependent PVT.

RESULTS

A total of 620 electrograms obtained in 131 patients were analyzed blindly by prospectively defined criteria for episodes of pause-dependent polymorphic VT. These were identified in 15/87 (17%) patients receiving dofetilide and 5/87 (6%) patients on placebo (p < 0.05). Five of these episodes were early (<3 days), all of which were TdP on dofetilide. There were 15 late events, 10 on dofetilide and five on placebo (p = 0.29). The median time to a late event was 22 days (range 6 to 107 days) for dofetilide and 99 days (range 34 to 207 days) for placebo.

CONCLUSIONS

Pause-dependent PVT was more common among patients receiving dofetilide, although total VT incidence was similar in the two groups. These data suggest that in ICD patients either long-term dofetilide therapy is associated with an increased risk of TdP or the drug alters VT morphology.

Polymorphic ventricular tachycardia, long Q-T syndrome, and torsades de pointes

PMVT is an uncommon arrhythmia with multiple causes. Classification and management are based on the Q-T interval. Torsades de pointes denotes PMVT in the setting of a prolonged Q-T interval and usually is iatrogenic in origin, although congenital LQTS is being recognized more frequently. Therapy of PMVT focuses on the establishment of hemodynamic stability, the removal or correction of precipitants, and the acute and long-term inhibition of subsequent episodes. Evaluation of these patients should include a thorough history and physical examination and an assessment for underlying heart disease and known [figure: see text] eliciting factors. Long-term management must be tailored to the individual and the underlying cause and should be conducted by an experienced cardiac electrophysiologist.

Successful catheter ablation in a patient with polymorphic ventricular tachycardia

We describe a patient with polymorphic ventricular tachycardia (PVT)/ventricular fibrillation (VF) without organic heart disease who was cured by radiofrequency catheter ablation. The patient was a 65-year-old woman with a 10-year history of recurrent syncope. There was no evidence of organic heart disease, and the QT interval during sinus rhythm was borderline normal (corrected QT interval = 0.45 sec1/2). ECG recording during syncope showed PVT. On one occasion, PVT degenerated into VF. This PVT was always induced by a premature ventricular complex (PVC) originating from the right ventricular (RV) outflow tract. Rapid pacing (220 beats/min) at the site of PVC origin reproduced polymorphic change of the QRS wave on surface ECG that was similar to PVT. This suggests that the PVT originated from a single focus in the RV outflow tract. Catheter ablation was performed at the site of PVC origin. During 18-month follow-up, PVT/VF was not documented.

Familial effort polymorphic ventricular arrhythmias in arrhythmogenic right ventricular cardiomyopathy map to chromosome 1q42-43

In the present study we report on another cause of an arrhythmia associated with familial arrhythmogenic right ventricular cardiomyopathy (ARVC), which is linked to chromosome 1q42-43. Two families with 48 subjects were studied with 12-lead electrocardiography, 24-hour ambulatory electrocardiography, chest x-ray, M-mode and 2-dimensional echocardiography, signal-averaging electrocardiography, and exercise stress testing. Six subjects also underwent right and left ventricular angiography and electrophysiologic study. An endomyocardial biopsy was performed in 1 subject. The genetic study included pedigree reconstruction and linkage analysis with polymorphic DNA markers. Five young subjects died suddenly during exercise; autopsy was performed in 3 and showed segmental fibro-fatty replacement of the right ventricle, mostly at the apex. Two of them experienced syncopal attacks during effort. Sixteen living subjects, without arrhythmias at rest had polymorphic ventricular arrhythmias during effort; ARVC was diagnosed in 15, whereas 1 did not have any demonstrable cardiac abnormality. The remaining family members were healthy and did not have arrhythmias. The linkage study assigned the disease locus to chromosome 1q42-q43, in close proximity to the alpha-actinin 2 locus (maximal lod score was 5.754 at theta = 0) with a 95% penetrance. Thus, these data suggest that effort-induced polymorphic ventricular arrhythmias and juvenile sudden death can be due to adrenergic stimulation in a particular genetic group of ARVC patients. In these cases the pathology was segmental, mostly localized to the right ventricular apex. Ventricular arrhythmias that are present in these families differ from the monomorphic ones that are usually seen in patients with ARVC.

Familial polymorphic ventricular arrhythmias: a quarter century of successful medical treatment based on serial exercise-pharmacologic testing

OBJECTIVES

We sought to determine whether objective tests of antiarrhythmic drug efficacy could produce favorable short- and long-term outcomes in a family with idiopathic malignant ventricular arrhythmias.

BACKGROUND

In 1973 a family presented with a history of several generations of syncopal spells and sudden death. Some individuals had nonspecific electrocardiographic (ECG) changes. Their QT intervals were normal at rest and with exercise. Autopsies in two young family members showed no cardiac abnormalities, specifically no evidence of arrhythmogenic right ventricular dysplasia, other cardiomyopathy, myocarditis or gross abnormality of the conduction system.

METHODS

Available family members had screening ECGs. Symptomatic members had a battery of tests, including electrophysiologic studies, ambulatory ECGs, audiograms, exercise stress testing, serum catecholamine levels during rest and exercise and isoproterenol infusion. Serial exercise-pharmacologic testing was performed in symptomatic family members until induction of an arrhythmia during exercise required higher work loads or became impossible.

RESULTS

Arrhythmias were not induced during electrophysiologic studies. In several family members tested, ventricular premature beats and then rapid polymorphic ventricular arrhythmias occurred whenever the sinus rate exceeded 130 beats/min. Emotional stress, isoproterenol infusion and exercise all elicited similar arrhythmias. Catecholamine levels during exercise were, however, unequivocally normal in two of three family members tested. Beta-blockers appeared to be the most effective pharmacologic agent for prevention of these arrhythmias. The efficacy of treatment has been confirmed during a follow-up of 25 years.

CONCLUSIONS

This family appears to have catecholamine hypersensitivity as the basis for their ventricular arrhythmias. Guided therapy using serial exercise-pharmacologic testing provided reliable protection for this familial ventricular arrhythmia during a 25-year follow-up.

Cardiac arrhythmias and the athlete

Athletes, although the healthiest segment of society, can develop cardiac arrhythmias. Benign bradycardias and atrial and ventricular premature contractions are common and seldom require treatment. Supraventricular tachycardias are less common and are usually not life-threatening, but do require treatment. Ventricular arrhythmias, although uncommon, are life-threatening and require treatment. Most athletes with ventricular arrhythmias have structural cardiac abnormalities, and further competitive play is usually prohibited. Commotio cordis, which is a recently described syndrome of sudden death caused by low-energy chest wall impact, may account for a significant percentage of the sudden deaths in athletes.