Further characterization of the syndrome of right bundle branch block, ST segment elevation, and sudden cardiac death

Cardiovascular adverse effects of antipsychotic drugs

Minor cardiovascular adverse effects from antipsychotic drugs are extremely common. They include effects such as postural hypotension and tachycardia due to anticholinergic or alpha1-adrenoceptor blockade, and may occur in the majority of patients at therapeutic dosages. There are a number of pharmacological effects that are of uncertain clinical significance, such as blockade of calmodulin, sodium and calcium channels and alpha2-adrenoceptors in the central nervous system. The most serious consequences of treatment, arrhythmias and sudden death, are probably uncommon and are most likely to be caused primarily by blockade of cardiac potassium channels such as HERG. Incomplete evidence suggests that arrhythmias and sudden death are a particular problem with certain drugs (thioridazine and droperidol), high risk populations (elderly, pre-existing cardiovascular disease, inherited disorders of cardiac ion channels or of antipsychotic drug metabolism) or people taking interacting drugs (such as drugs that prolong the QT interval, e.g. tricyclic antidepressants, drugs that inhibit antipsychotic drug metabolism, or diuretics). Clozapine may be unique in also causing death from myocarditis and cardiomyopathy. Much further research is required to more clearly identify high risk drugs and the populations that are at risk of sudden death, as well as the mechanisms involved and the extent of the risk.

Brugada-type electrocardiographic pattern induced by cocaine

Right bundle branch block with coved ST-segment elevation in leads V1 through V3 is the electrocardiographic (ECG) marker of the Brugada syndrome. We describe a healthy young man with a normal baseline ECG in whom a transient Brugada pattern was observed repeatedly after recreational cocaine use. Intravenous administration of procainamide and subsequent intravenous propranolol followed by noradrenaline failed to reproduce the Brugada sign. An electrophysiologic study performed in the presence of the Brugada ECG pattern showed no inducible arrhythmias. This case illustrates that, in susceptible individuals, cocaine may provoke the Brugada sign. The clinical importance of this cocaine-induced ECG abnormality is currently unknown.

Clinical characteristics of patients with spontaneous or inducible ventricular fibrillation without apparent heart disease presenting with J wave and ST segment elevation in inferior leads

INTRODUCTION

The clinical characteristics of three patients with spontaneous or inducible ventricular fibrillation (VF) without apparent heart disease, who presented with J wave and ST segment elevation in inferior leads, are described.

METHODS AND RESULTS

All patients were male and experienced syncope. Their symptoms occurred at night or early in the morning. Holter ECG revealed infrequent premature ventricular complexes. Injection with disopyramide 2 mg/kg augmented ST segment elevation.

CONCLUSION

These characteristics were very similar to those of patients with Brugada syndrome. These three patients with these specific features might have a variant of Brugada syndrome.

[Recurrent ventricular fibrillation during a febrile illness in a patient with the Brugada syndrome]

Different situations have been involved in the origin of ventricular arrhythmic events in patients with the Brugada syndrome such as bradycardia, alcohol consumption and mental stress. We present a 30 year old male with recurrent ventricular fibrillation due to a febrile illness with intense sweating. He had been previously studied at our Unit in 1995 because of an episode of resuscitated cardiac arrest due to ventricular fibrillation. The twelve-lead electrocardiogram showed the typical characteristics of a patient with the Brugada syndrome. Different invasive and non-invasive tests performed were normal. He received a defibrillator and had no recurrences during 4 years of follow up. In March,1999, after an upper respiratory tract infection he had high fever treated with paracetamol but at down he had sweating and chills, followed by 3 defibrillator shocks. Late interrogation showed 5 episodes of ventricular fibrillation, two of them non-sustained, and the rest adequately treated by the defibrillator. Activation and inactivation kinetics for early INa are twofold faster at higher temperature, and shift activation and steady-state inactivation. This may explain the role of the temperature as a trigger for ventricular arrhythmias in our patient.

Body surface distribution and response to drugs of ST segment elevation in Brugada syndrome: clinical implication of eighty-seven-lead body surface potential mapping and its application to twelve-lead electrocardiograms

INTRODUCTION

Body surface distribution and magnitude of ST segment elevation and their reflection in 12-lead ECGs have not been clarified in Brugada syndrome.

METHODS AND RESULTS

Eighty-seven-lead body surface potential mapping and 12-lead ECGs were recorded simultaneously in 25 patients with Brugada syndrome and 40 control patients. The amplitude of the ST segment 20 msec after the end of QRS (ST20) was measured from all 87 leads, and an ST isopotential map was constructed. The maximum ST elevation (maxST20) was distributed in an area of the right ventricular outflow tract in all Brugada patients, and it was larger than that in control patients (0.37 +/- 0.13 vs 0.12 +/- 0.04 mV; P < 0.0005). The maximum was observed on the level of the parasternal fourth intercostal space, on which the V1 and V2 leads of the standard 12-lead ECG were located, in 18 of the 25 Brugada patients in whom typical coved- or saddleback-type ST elevation was seen in leads V1 and V2. The maximum was located on the second intercostal space in the remaining seven Brugada patients in whom only a mild saddleback-type ST elevation was seen in leads V1 and V2 of the 12-lead ECG. Typical ST segment elevation was recognized in leads V1 and V2, which were recorded on the second or third intercostal space. ST elevation in Brugada patients was dramatically normalized by isoproterenol, a beta-adrenergic agonist (maxST20 = 0.17 +/- 0.08 mV; P < 0.0005 vs control conditions), and accentuated by disopyramide, an Na+ channel blocker (maxST20 = 0.50 +/- 0.15 mV; P < 0.0005 vs control conditions), without any change in the location of the maxST20.

CONCLUSION

Our data indicate that recordings of leads V1-V3 of the 12-lead ECG on the parasternal second or third intercostal space would be helpful in diagnosing suspected patients with Brugada syndrome. The data suggest that Na+ channel blockers are capable of accentuating ST elevation in leads V1-V3.

Transmural dispersion of repolarization and arrhythmogenicity: the Brugada syndrome versus the long QT syndrome

Recent studies have shown that ventricular myocardium is composed of at least 3 electrophysiologically distinct cell types: epicardial, endocardial, and M cells. Action potentials recorded from epicardial and M cells, unlike those recorded from endocardium, display a spike-and-dome morphology, the result of a prominent transient outward current-mediated phase 1. M cells are distinguished from endocardial and epicardial cells by the ability of their action potential to prolong disproportionately in response to a slowing of rate and/or to agents with class III actions. This intrinsic electrical heterogeneity contributes to the inscription of the electrocardiogram as well as to the development of a variety of cardiac arrhythmias. The transmural dispersion of repolarization is in large part responsible for the inscription of the J wave and T wave of the electrocardiogram. Because full repolarization of epicardium defines the peak of the T wave and that of the M cells, the end of the T wave, the interval between the peak and the end of the T wave provides a valuable index of transmural dispersion of repolarization. Differences in the response of the 3 cell types to pharmacologic agents and/or pathophysiological states often results in amplification of intrinsic electrical heterogeneities, thus providing a substrate as well as a trigger for the development of reentrant arrhythmias, including torsade de pointes (TdP) commonly associated with the long QT syndrome (LQTS) and the polymorphic ventricular tachycardia/fibrillation encountered in patients with the Brugada syndrome. Early repolarization of the epicardial action potential results in abnormal abbreviation of action potential duration due to an all-or-none repolarization at the end of phase 1 of the epicardial action potential. The loss of the action potential dome in epicardium but not endocardium gives rise to a large dispersion of repolarization across the ventricular wall, resulting in a transmural voltage gradient that manifests in the electrocardiogram as an ST segment elevation (or idiopathic J wave). Under these conditions, heterogeneous repolarization of the epicardial action potential gives rise to phase 2 reentry, which provides an extrasystole capable of precipitating ventricular tachycardia/fibrillation (or rapid TdP). Experimental models displaying these phenomena show electrocardiographic characteristics similar to those of the Brugada syndrome as well as those encountered during acute ischemia. Transmural dispersion of repolarization is also greatly amplified in LQTS. Disproportionate prolongation of the M-cell action potential contributes to the development of long QT intervals, wide-based or notched T waves, and a large transmural dispersion of repolarization, which provides the substrate for the development of a polymorphic ventricular tachycardia closely resembling torsade de pointes. An early afterdepolarization-induced triggered beat is thought to provide the extrasystole that precipitates TdP. Pharmacologic models of the LQT1, LQT2 and LQT3 forms of LQTS mimic the distinctive electrocardiographic, electrophysiologic, and pharmacologic responses observed in patients with these 3 different genetic syndromes. In LQTS, as in the Brugada syndrome, a mutation in an ion channel gene (in some cases the same gene--SCN5A) is responsible for the development of a large transmural dispersion of repolarization, which serves to provide the arrhythmogenic substrate tha can lead to sudden death.

Unmasking effect of propafenone on the concealed form of the Brugada phenomenon

A case report of a patient with frequent ventricular premature beats but with an otherwise normal ECG and no structural heart disease. Propafenone in therapeutical doses unmasked the ECG picture of the Brugada phenomenon.

Sodium channel blockers identify risk for sudden death in patients with ST-segment elevation and right bundle branch block but structurally normal hearts

BACKGROUND

A mutation in the cardiac sodium channel gene (SCN5A) has been described in patients with the syndrome of right bundle branch block, ST-segment elevation in leads V1 to V3, and sudden death (Brugada syndrome). These electrocardiographic manifestations are transient in many patients with the syndrome. The present study examined arrhythmic risk in patients with overt and concealed forms of the disease and the effectiveness of sodium channel blockers to unmask the syndrome and, thus, identify patients at risk.

METHODS AND RESULTS

The effect of intravenous ajmaline (1 mg/kg), procainamide (10 mg/kg), or flecainide (2 mg/kg) on the ECG was studied in 34 patients with the syndrome and transient normalization of the ECG (group A), 11 members of 3 families in whom a SCN5A mutation was associated with the syndrome and 8 members in whom it was not (group B), and 53 control subjects (group C). Ajmaline, procainamide, or flecainide administration resulted in ST-segment elevation and right bundle branch block in all patients in group A and in all 11 patients with the mutation in group B. A similar pattern could not be elicited in the 8 patients in group B who lacked the mutation or in any person in group C. The follow-up period (37+/-33 months) revealed no differences in the incidence of arrhythmia between the 34 patients in whom the phenotypic manifestation of the syndrome was transient and the 24 patients in whom it was persistent (log-rank, 0.639).

CONCLUSIONS

The data demonstrated a similar incidence of potentially lethal arrhythmias in patients displaying transient versus persistent ST-segment elevation and right bundle branch block, as well as the effectiveness of sodium channel blockers to unmask the syndrome and, thus, identify patients at risk.

SCN5A mutation (T1620M) causing Brugada syndrome exhibits different phenotypes when expressed in Xenopus oocytes and mammalian cells

Brugada syndrome is a hereditary cardiac disease causing abnormal ST segment elevation in the ECG, right bundle branch block, ventricular fibrillation and sudden death. In this study we characterized a new mutation in the SCN5A gene (T1620M), causing the Brugada syndrome. The mutated channels were expressed in both Xenopus leavis oocytes and in mammalian tsA201 cells with and without the beta-subunit and studied using the patch clamp technique. Opposite phenotypes were observed depending on the expression system. T1620M mutation led to a faster recovery from inactivation and a shift of steady-state inactivation to more positive voltages when expressed in Xenopus oocytes. However, using the mammalian expression system no effect on steady-state inactivation was observed, but this mutation led to a slower recovery from inactivation. Our finding supports the idea that the slower recovery from inactivation of the cardiac sodium channels seen in our mammalian expression system could decrease the density of sodium channels during the cardiac cycle explaining the in vivo arrhythmogenesis in patients with Brugada syndrome.

[Multiple changes of the morphology of ST segment in a patient with Brugada syndrome]

The Brugada syndrome is characterized by in a electrocardiographic pattern of right bundle branch block and ST-segment elevation in the right precordial leads, absence of any structural heart disease and syncope episodes or sudden death. We report the case of a 50 year-old men with Brugada syndrome and manifold changes of the precordial morphology of ST segment.

Molecular biology of arrhythmic syndromes

In this review, the up-to-date understanding of the molecular basis of primary ventricular arrhythmias will be outlined. Two disorders have recently been well described at the molecular level, the long QT syndromes and Brugada syndrome, and in this paper we review the current scientific knowledge of each disease.

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.

Cellular basis for the Brugada syndrome and other mechanisms of arrhythmogenesis associated with ST-segment elevation

BACKGROUND

The Brugada syndrome is characterized by marked ST-segment elevation in the right precordial ECG leads and is associated with a high incidence of sudden and unexpected arrhythmic death. Our study examines the cellular basis for this syndrome.

METHODS AND RESULTS

Using arterially perfused wedges of canine right ventricle (RV), we simultaneously recorded transmembrane action potentials from 2 epicardial and 1 endocardial sites, together with unipolar electrograms and a transmural ECG. Loss of the action potential dome in epicardium but not endocardium after exposure to pinacidil (2 to 5 micromol/L), a K(+) channel opener, or the combination of a Na(+) channel blocker (flecainide, 7 micromol/L) and acetylcholine (ACh, 2 to 3 micromol/L) resulted in an abbreviation of epicardial response and a transmural dispersion of repolarization, which caused an ST-segment elevation in the ECG. ACh facilitated loss of the action potential dome, whereas isoproterenol (0.1 to 1 micromol/L) restored the epicardial dome, thus reducing or eliminating the ST-segment elevation. Heterogeneous loss of the dome caused a marked dispersion of repolarization within the epicardium and transmurally, thus giving rise to phase 2 reentrant extrasystole, which precipitated ventricular tachycardia (VT) and ventricular fibrillation (VF). Transient outward current (I(to)) block with 4-aminopyridine (1 to 2 mmol/L) or quinidine (5 micromol/L) restored the dome, normalized the ST segment, and prevented VT/VF. Conclusions-Depression or loss of the action potential dome in RV epicardium creates a transmural voltage gradient that may be responsible for the ST-segment elevation observed in the Brugada syndrome and other syndromes exhibiting similar ECG manifestations. Our results also demonstrate that extrasystolic activity due to phase 2 reentry can arise in the intact wall of the canine RV and serve as the trigger for VT/VF. Our data point to I(to) block (4-aminopyridine, quinidine) as an effective pharmacological treatment.

A young man with recurrent syncopes, right bundle branch block and ST segment elevation

We report on the case of a 33-year-old man with recurrent syncopes appearing suddenly due to sustained monomorphic ventricular tachycardias. The electrocardiogram (ECG) showed a right bundle branch block pattern and ST segment elevation in the precordial leads V1 to V2, not explained by ischemia, electrolyte disturbances, toxic ingestion, or structural heart disease (coronary and right ventricle angiograms as well as biopsies of the right ventricle were normal). ECG image was compatible with the so-called Brugada syndrome, first described in 1992. This entity is very rare. Missed diagnosis can be disastrous because life-threatening ventricular arrhythmias often develop in patients.

Heart Block and Conduction Disturbances

Heart block and conduction disturbances appear to be relatively common in the general population. Because many individuals with conduction system disease are asymptomatic and never seek medical attention, our knowledge of the natural history of these disorders comes from large population-based studies. Because conduction system disease is a heterogeneous entity of diverse causes, treatment options may vary from individual to individual, depending on the specific cause and the clinical manifestations. Permanent pacing is the cornerstone of treatment for most patients with symptomatic conduction system disease. Recent technologic improvements in permanent pacing systems have made this option more attractive, although there are situations in which other therapeutic options may be considered. Specific therapy is not necessary in all patients with conduction system disease, especially those without symptoms. Of those requiring treatment, medication may be helpful in certain situations, but pacemakers remain the mainstay of therapy in most. Recent advances in the therapy of ischemic heart disease (eg, thrombolytic agents and reperfusion techniques) show some promise in arresting or even reversing some forms of conduction system disease, but these techniques require further study.

Asymptomatic form of Brugada syndrome

We describe a patient with the asymptomatic form of Brugada syndrome. His electrographical, electropharmacological, and electrophysiological characteristics were similar to those reported in patients with the symptomatic form of Brugada syndrome. We believe that he has the same arrhythmogenic substrate as that of patients with Brugada syndrome. The fact that he had no episode of spontaneous ventricular fibrillation might be explained by his absence of the triggering factors.

Transient local changes in right ventricular monophasic action potentials due to ajmaline in a patient with Brugada Syndrome

A 48-year-old patient with recurrent episodes of palpitations and syncope presented with transient ST segment elevation in the right precordial ECG leads. Structural heart disease was excluded. No arrhythmias were inducible by programmed ventricular stimulation. Parallel to ST elevation after intravenous ajmaline, a gradual and reversible delay in the upstroke of right ventricular (RV) monophasic action potentials (MAPs) occurred that was most marked in the RV outflow tract and nearly absent at right free-wall recordings. Ajmaline led to a cycle length-dependent increase in RV dispersion of repolarization. Thus, right endocardial MAPs may demonstrate regionally different action potential changes that may contribute to the ECG changes in Brugada syndrome.

A case of vasospastic angina presenting Brugada-type ECG abnormalities

An electrophysiological study and a provocative test of coronary artery spasm was attempted in a 68-year-old man who was having syncopal attacks and chest pain. His electrocardiogram had the characteristics of Brugada syndrome and ventricular fibrillation (VF) was induced by programmed electrical stimulation. ST-segment elevation became exaggerated by procainamide, which could not prevent the induction of VF. Coronary angiography revealed no stenotic lesions, and spasm in the left coronary artery was induced by intracoronary administration of acetylcholine with similar chest pain to that experienced before. Under treatment with diltiazem and flecainide, which suppressed the induction of VF, the patient experienced no recurrence of symptoms despite persistent ST-segment elevation. No previous reports have described coronary spasm associated with Brugada-type ECG abnormalities, and patients with syncope should be evaluated carefully.

Ion channels and ventricular arrhythmias: cellular and ionic mechanisms underlying the Brugada syndrome

Brugada syndrome is characterized by ST segment elevation in the right precordial leads, V1-V3 (unrelated to ischemia or structural disease), normal QT intervals, apparent right bundle branch block, and sudden cardiac death, particularly in men of Asian origin. An autosomal dominant mode of inheritance with variable expression has been described. The only gene thus far linked to the Brugada syndrome is the cardiac sodium channel gene, SCN5A. The possible cellular and ionic basis for these features of the Brugada syndrome are discussed. Strong sodium channel block, among other modalities, has been shown to be capable of inducing epicardial and transmural dispersion of repolarization, thus providing the substrate for the development of phase 2 and circus movement reentry, which underlies ventricular tachycardia/ventricular fibrillation.

Idiopathic ventricular tachycardia

Most ventricular tachycardias encountered in clinical practice occur in patients who have structural heart disease. Idiopathic ventricular tachycardia refers to those arrhythmias that occur in patients without structural heart disease, metabolic/electrolyte abnormalities, or the long QT syndrome. Three commonly recognized forms of idiopathic ventricular tachycardia include: (a) ventricular tachycardia associated with mitral valve prolapse, (b) ventricular tachycardia originating from the right ventricular outflow tract, and (c) ventricular tachycardia originating from the left ventricle. Recently, a fourth type of idiopathic ventricular tachycardia, termed the Brugada syndrome, has been identified as responsible for some cases of cardiac arrest in persons without apparent structural heart disease. Each form of ventricular tachycardia may be considered a discrete syndrome based on its electrocardiographic characteristics, mechanisms, responses to pharmacologic intervention, and prognosis (good in most cases). Ventricular tachycardias range from the common to the exotic, but all represent syndromes with which the internist and general cardiologist should be familiar.

ST segment elevation in the right precordial leads induced with class IC antiarrhythmic drugs: insight into the mechanism of Brugada syndrome

We evaluated two patients without previous episodes of syncope who showed characteristic ECG changes similar to Brugada syndrome following administration of Class IC drugs, flecainide and pilsicainide, but not following Class IA drugs. Patient 1 had frequent episodes of paroxysmal atrial fibrillation resistant to Class IA drugs. After treatment with flecainide, the ECG showed a marked ST elevation in leads V2 and V3, and the coved-type configuration of ST segment in lead V2. A signal-averaged ECG showed late potentials that became more prominent after flecainide. Pilsicainide, a Class IC drug, induced the same ST segment elevation as flecainide, but procainamide did not. Patient 2 also had frequent episodes of paroxysmal atrial fibrillation. Pilsicainide changed atrial fibrillation to atrial flutter with 2:1 ventricular response, and the ECG showed right bundle branch block and a marked coved-type ST elevation in leads V1 and V2. After termination of atrial flutter, ST segment elevation in leads V1 and V2 continued. In this patient, procainamide and quinidine did not induce this type of ECG change. In conclusion, strong Na channel blocking drugs induce ST segment elevation similar to Brugada syndrome even in patients without any history of syncope or ventricular fibrillation.

The Brugada syndrome: clinical, electrophysiologic and genetic aspects

This review deals with the clinical, basic and genetic aspects of a recently highlighted form of idiopathic ventricular fibrillation known as the Brugada syndrome. Our primary objective in this review is to identify the full scope of the syndrome and attempt to correlate the electrocardiographic manifestations of the Brugada syndrome with cellular and ionic heterogeneity known to exist within the heart under normal and pathophysiologic conditions so as to identify the cellular basis and thus potential diagnostic and therapeutic approaches. The available data suggest that the Brugada syndrome is a primary electrical disease resulting in abnormal electrophysiologic activity in right ventricular epicardium. Recent genetic data linking the Brugada syndrome to an ion channel gene mutation (SCN5A) provides further support for the hypothesis. The electrocardiographic manifestations of the Brugada syndrome show transient normalization in many patients, but can be unmasked using sodium channel blockers such as flecainide, ajmaline or procainamide, thus identifying patients at risk. The available data suggest that loss of the action potential dome in right ventricular epicardium but not endocardium underlies the ST segment elevation seen in the Brugada syndrome and that electrical heterogeneity within right ventricular epicardium leads to the development of closely coupled premature ventricular contractions via a phase 2 reentrant mechanism that then precipitates ventricular tachycardia/ventricular fibrillation (VT/VF). Currently, implantable cardiac defibrillator implantation is the only proven effective therapy in preventing sudden death in patients with the Brugada syndrome and is indicated in symptomatic patients and should be considered in asymptomatic patients in whom VT/VF is inducible at time of electrophysiologic study.

The Brugada syndrome in a Chinese population

Sudden cardiac death has been reported in patients with a unique electrocardiographic (ECG) abnormality showing right bundle branch block and ST segment elevation in the precordial leads. This syndrome was first described by Brugada and Brugada and has not been previously described in a Chinese population. We report here the first three cases in Singapore. The first patient was a 49-year-old man who presented with syncope, associated with generalized convulsions. The second patient was a 25-year-old man who complained of palpitations but no syncope. The third patient was a 77-year-old man who presented with recurrent episodes of syncope and collapsed with ventricular fibrillation. All patients had no past cardiac or drug history of note. The neurological examination and investigations were normal. All three patients showed a unique right bundle branch block pattern with ST segment elevation in leads V1-3. The echocardiogram and 24-h ambulatory ECG monitoring, were normal. Single vessel disease was present in the third patient. Electrophysiological studies performed in all three patients were able to induce ventricular fibrillation. The patient with resuscitated cardiac death underwent an implantable cardioverter defibrillator implantation. The importance of this syndrome is that the recognition of the unique ECG pattern enables early identification and treatment of these patients.

Familial sudden cardiac death associated with a terminal QRS abnormality on surface 12-lead electrocardiogram in the index case

A case is presented of an 18-year-old male who had been resuscitated following an episode of sudden death due to ventricular fibrillation. The patient was noted to have an abnormal deflection in the terminal QRS on surface ECG and an abnormal signal-averaged ECG demonstrating a late potential coincident with the terminal QRS abnormality on the ECG. The patient had easily inducible polymorphic ventricular tachycardia during electrophysiologic study, which was suppressed by quinidine but not by procainamide or beta blockers. The surface ECG and signal-averaged ECG also were normalized by quinidine but not by procainamide or beta blockers. The patient had no further arrhythmias on quinidine for 6 years until he inexplicably discontinued his medication and died suddenly shortly thereafter. The present case may represent a unique familial sudden death syndrome or possibly a variant of the sudden death syndrome associated with right bundle branch block and ST elevation in V1 through V3. Currently available data suggest that, in such patients, an implantable cardioverter defibrillator may provide better protection from sudden death than does antiarrhythmic drug therapy.

Dynamic changes of 12-lead electrocardiograms in a patient with Brugada syndrome

We present a patient with Brugada syndrome in whom 12-lead ECGs were recorded just before and after an episode of ventricular fibrillation (VF). A progressive elevation of both the RS-T segment and J waves just preceding and following the VF, and a close relationship between the amplitude of the RS-T segment and the preceding R-R intervals during atrial fibrillation, were documented. These findings support the hypothesis that RS-T elevation and a subsequent VF are related to a transient outward current-mediated spike-and-dome morphology of the epicardial action potential.

Genetic basis and molecular mechanism for idiopathic ventricular fibrillation

Ventricular fibrillation causes more than 300,000 sudden deaths each year in the USA alone. In approximately 5-12% of these cases, there are no demonstrable cardiac or non-cardiac causes to account for the episode, which is therefore classified as idiopathic ventricular fibrillation (IVF). A distinct group of IVF patients has been found to present with a characteristic electrocardiographic pattern. Because of the small size of most pedigrees and the high incidence of sudden death, however, molecular genetic studies of IVF have not yet been done. Because IVF causes cardiac rhythm disturbance, we investigated whether malfunction of ion channels could cause the disorder by studying mutations in the cardiac sodium channel gene SCN5A. We have now identified a missense mutation, a splice-donor mutation, and a frameshift mutation in the coding region of SCN5A in three IVF families. We show that sodium channels with the missense mutation recover from inactivation more rapidly than normal and that the frameshift mutation causes the sodium channel to be non-functional. Our results indicate that mutations in cardiac ion-channel genes contribute to the risk of developing IVF.

Right bundle-branch block and ST-segment elevation in leads V1 through V3: a marker for sudden death in patients without demonstrable structural heart disease

BACKGROUND

Five years ago, we described a specific ECG pattern of right bundle-branch block and ST-segment elevation in leads V1 through V3 associated with sudden death in patients without demonstrable structural heart disease. Information on long-term outcome has become available due to pooled data on a large cohort of patients with this syndrome who are followed at 33 centers worldwide.

METHODS AND RESULTS

Data on 63 patients (57 men; mean age, 38+/-17 years) with the described ECG pattern were analyzed in terms of arrhythmic events and sudden death. Events were analyzed for patients with at least one episode of aborted sudden death or syncope of unknown origin before recognition of the syndrome (symptomatic patients, n=41) and for patients in whom the ECG pattern was recognized by chance or because of screening related to sudden death of a relative (asymptomatic patients, n=22). During a mean follow-up of 34+/-32 months, an arrhythmic event occurred in 14 symptomatic patients (34%) and 6 asymptomatic patients (27%). An automatic defibrillator was implanted in 35 patients, 15 received pharmacological therapy with beta-blockers and/or amiodarone, and 13 did not receive treatment The incidence of arrhythmic events was similar in all therapy groups (log-rank 0.86); however, total mortality was 0% in the implantable defibrillator group, 26% in the pharmacological group, and 31% in the no therapy group (log-rank 0.0005). All mortality was due to sudden death.

CONCLUSIONS

Patients without demonstrable structural heart disease and an ECG pattern of right bundle-branch block and ST-segment elevation in leads V1 through V3 are at risk for sudden death. Amiodarone and/or beta-blockers do not protect them against sudden death, and an implantable defibrillator seems to be the present treatment of choice.

Increased dispersion of repolarization time determined by monophasic action potentials in two patients with familial idiopathic ventricular fibrillation

INTRODUCTION

The role of increased dispersion of repolarization in the genesis of torsades de pointes in patients with long QT syndrome has been clarified, but its role in the genesis of idiopathic ventricular fibrillation (VF) is not yet known. To investigate the pathogenesis of VF, we recorded monophasic action potentials (MAPs) from two siblings (48- and 36-year-old males) with familial idiopathic VF.

METHODS AND RESULTS

The elder brother (patient 1) showed a late r' wave in lead V1 and ST segment elevation in leads V1 through V3. The younger brother (patient 2) had late r' waves and ST segment elevation in leads II, III, and aVF, and the configurations were very similar to those of patient 1. MAPs were recorded from several sites in the right ventricular (RV) and left ventricular (LV) endocardium during constant right atrial pacing. The repolarization time (RT) was defined as the sum of the activation time (AT) and action potential duration (APD) at 90% repolarization. In patient 1, marked prolongation of the AT (140 msec) and the RT (380 msec) was recorded in the RV septum of the outflow tract, and the RT dispersion was markedly increased (125 msec). In contrast, patient 2 showed prolongation of the AT (80 msec) and RT (310 msec), and fractionated electrograms in the RV floor of the inflow tract. The RT dispersion was also increased (80 msec). VF and nonsustained polymorphic ventricular tachycardia were induced by double premature stimulation in patients 1 and 2, respectively. Chronic amiodarone therapy decreased the RT dispersion and suppressed the induction of ventricular tachyarrhythmias in patient 2, although late r' waves and slight ST segment elevation were unmasked in leads V1 and V2.

CONCLUSION

Our data suggest that the increased dispersion of the RT, which was due mainly to a localized conduction delay in the RV, created an arrhythmogenic substrate in the two patients with familial idiopathic VF.