Ventricular fibrillation in patients without significant structural heart disease: a multicenter experience with implantable cardioverter-defibrillator therapy

The yield of a comprehensive investigation protocol for the diagnosis of true idiopathic ventricular fibrillation in a real-life clinical setting

Traditionally, aborted cardiac arrest (ACA) due to documented ventricular fibrillation (VF) in the absence of structural heart disease has been termed idiopathic VF. By careful evaluation, a specific etiology can be found in a substantial proportion of patients. The aim of this survey was to assess the yield of an advanced diagnostic work-up to reveal a causative etiology in a real-life clinical setting. Patients from the University Hospital Brno's ACA database were analyzed (514 patients in total). Forty-six patients (31 males) fulfilled the inclusion criteria, which were: (1) absence of structural pathology on echocardiography; (2) absence of coronary artery disease; and (3) absence of reversible cause of ACA. The diagnostic work-up consisted in cardiac magnetic resonance imaging, stress testing, sodium channel blocker challenge, and genetic testing according to the availability of the method and patient compliance. A specific disease was found in 17 individuals (37.0%), although at least one diagnostic step was refused by 13 patients (28.3%). True idiopathic VF was confirmed in 7 patients (15.2%), for whom the entire diagnostic work-up did not reveal any specific pathology. Our real-life survey shows that, even with an incomplete diagnostic work-up (due to the unavailability of a particular method or variable patient compliance), a specific diagnosis can be identified in more than one third of the cases of "idiopathic" VF, which can thus enable targeted treatment and family screening.

Inherited arrhythmia syndrome predisposing to sudden cardiac death

Inherited arrhythmia (IA) is one of the main causes of sudden cardiac death (SCD) in young people, and is reported to be a more prevalent cause of SCD in Asia than in Western countries. IAs are a group of genetic disorders caused by mutations in genes encoding cardiac ion channels, leading to electrophysiological characteristics that often occur in the absence of structural abnormalities. Channelopathies, such as long QT syndrome and Brugada syndrome, carry a potential risk of life-threatening ventricular tachyarrhythmias that predispose to SCD, although early prediction and prevention of the risk remain challenging. Recent advances in genetic testing have facilitated risk stratification as well as a precise diagnosis for IA, despite ongoing debates about the implications. Herein, we provide epidemiological data, a pathophysiological overview, and the current clinical approach to IAs related to SCD. In addition, we review the general issues arising from genetic testing for IAs.

Idiopathic Ventricular Fibrillation: Diagnosis, Ablation of Triggers, Gaps in Knowledge, and Future Directions

Idiopathic ventricular fibrillation (IVF) is a diagnosis of exclusion made when no underlying cause is identified in a cardiac arrest survivor. Although the frequency of this diagnosis has declined over time due to advances in diagnostic techniques, it remains a substantial cause of sudden cardiac arrest. Further, IVF tends to recur. This article reviews the criteria for diagnosis, patient characteristics, the two primary arrhythmic phenotypes—short-coupled variant of torsades de pointes and recurrent paroxysmal IVF—and the electrophysiologic features, treatment, and ablation of premature ventricular complexes that can trigger IVF.

Long-Term Outcome of Patients Initially Diagnosed With Idiopathic Ventricular Fibrillation

Background—

Idiopathic ventricular fibrillation (IVF) is a rare cause of sudden cardiac arrest. Limited data are available on the long-term outcome of IVF patients.

Methods and Results—

In this retrospective cohort study, 107 consecutive patients with an initial diagnosis of IVF were analyzed (age at index event 40.4 years, 60% male). Missing diagnostic data were acquired during follow-up, including genetic testing, to exclude underlying disease. A specific diagnosis was revealed in 22 of 107 patients (21%) during a median follow-up of 10.2 years. Mortality rate was 9% in IVF patients (8/85). Appropriate implantable cardioverter–defibrillator therapy was delivered in 23 patients (29%) of 78 IVF patients with an implantable cardioverter–defibrillator, with a median of 3 appropriate shocks per patient.

Conclusions—

One fifth of the patients initially diagnosed with IVF reveal a specific diagnosis during long-term follow-up. Additional diagnostic testing, including genetic testing, contributes to the detection of specific diseases. The recurrence rate of ventricular arrhythmias in IVF patients is high. Our data show the importance of thorough follow-up and reassessment of diagnosis in IVF patients.

Radiofrequency Ablation to Prevent Sudden Cardiac Death

Radiofrequency ablation may prevent or treat atrial and ventricular arrhythmias. Since some of these arrhythmias are associated with sudden cardiac death, it has been hypothesized that ablation may prevent sudden death in certain cases. We performed a literature search to better understand under which circumstances ablation may prevent sudden death and found little randomized data demonstrating the long-term effects of ablation. Current literature shows that ablation clearly prevents symptoms of arrhythmia and may reduce the incidence of sudden cardiac death in select patients, although data does not indicate improved mortality. Ongoing clinical trials are needed to better define the role of ablation in preventing sudden cardiac death.

Short-coupled polymorphic ventricular tachycardia at rest linked to a novel ryanodine receptor (RyR2) mutation: leaky RyR2 channels under non-stress conditions

BACKGROUND

Ryanodine receptor (RyR2) mutations have largely been associated with catecholaminergic polymorphic ventricular tachycardia (PMVT). The role of RyR2 mutations in the pathogenesis of arrhythmias and syncope at rest is unknown. We sought to characterize the clinical and functional characteristics associated with a novel RyR2 mutation found in a mother and daughter with PMVT at rest.

METHODS AND RESULTS

A 31-year-old female with syncope at rest and recurrent short-coupled premature ventricular contractions (PVCs) initiating PMVT was found to be heterozygous for a novel RyR2-H29D mutation. Her mother, who also had syncope at rest and short-coupled PMVT, was found to harbor the same mutation. Human RyR2-H29D mutant channels were generated using site-directed mutagenesis and heterologously expressed in HEK293 cells together with the stabilizing protein calstabin2 (FKPB12.6). Single channel measurements of RyR2-H29D mutant channels and wild type (WT) RyR2 channels were compared at varying concentrations of cytosolic Ca(2+). Binding affinities of the RyR2-H29D channels and RyR2-WT channels to calstabin2 were compared. Functional characterization of the RyR2-H29D mutant channel revealed significantly higher open probability and opening frequency at diastolic levels of cytosolic Ca(2+) under non-stress conditions without protein kinase A treatment. This was associated with a modest depletion of calstabin2 binding under resting conditions.

CONCLUSIONS

The RyR2-H29D mutation is associated with a clinical phenotype of short-coupled PMVT at rest. In contrast to catecholaminergic PMVT-associated RyR2 mutations, RyR2-H29D causes a leaky channel at diastolic levels of Ca(2+) under non-stress conditions. Leaky RyR2 may be an under-recognized mechanism for idiopathic PMVT at rest.

Videoscopic left cardiac sympathetic denervation for patients with recurrent ventricular fibrillation/malignant ventricular arrhythmia syndromes besides congenital long-QT syndrome

BACKGROUND

Treatment options for patients with recurrent ventricular arrhythmias refractory to pharmacotherapy and ablation are minimal. Although left cardiac sympathetic denervation (LCSD) is well established in long-QT syndrome, its role in non-long-QT syndrome arrhythmogenic channelopathies and cardiomyopathies is less clear. Here, we report our single-center experience in performing LCSD in this setting.

METHODS AND RESULTS

In this institutional review board-approved study, we retrospectively reviewed the electronic medical records of all patients (N=91) who had videoscopic LCSD at our institution from 2005 to 2011. Data were analyzed for the subset (n=27) who were denervated for an underlying diagnosis other than autosomal dominant or sporadic long-QT syndrome. The spectrum of arrhythmogenic disease included catecholaminergic polymorphic ventricular tachycardia (n=13), Jervell and Lange-Nielsen syndrome (n=5), idiopathic ventricular fibrillation (n=4), left ventricular noncompaction (n=2), hypertrophic cardiomyopathy (n=1), ischemic cardiomyopathy (n=1), and arrhythmogenic right ventricular cardiomyopathy (n=1). Five patients had LCSD because of high-risk assessment and β-blocker intolerance, none of whom had a sentinel breakthrough cardiac event at early follow-up. Among the remaining 22 previously symptomatic patients who had LCSD as secondary prevention, all had an attenuation in cardiac events, with 18 having no breakthrough cardiac events so far and 4 having experienced ≥1 post-LCSD breakthrough cardiac event.

CONCLUSIONS

LCSD may represent a substrate-independent antifibrillatory treatment option for patients with life-threatening ventricular arrhythmia syndromes other than long-QT syndrome. The early follow-up seems promising, with a marked reduction in the frequency of cardiac events postdenervation.

Monomorphic and polymorphic ventricular tachycardias arising from the His–Purkinje system: what do we know?

Monomorphic and polymorphic Purkinje-related ventricular tachycardias (VTs) may occur in patients with and without underlying structural heart disease. Monomorphic Purkinje-related VTs can be divided into different entities: verapamil-sensitive left fascicular VTs; bundle branch reentry tachycardias (BBRT); interfascicular VTs and focal Purkinje VTs. The most frequent fascicular VT is left posterior fascicular VT, characterized by macro-reentry within the posterior Purkinje network. However, the reentry may also be located in the anterior Purkinje network (left anterior fascicular VT). BBRT is also a macro-reentry-tachycardia, utilizing both the right and the left bundle branch as the antegrade and the retrograde limb and is often associated with pre-existing conduction disturbances in the specific conduction system. Interfascicular VT is rare and characterized by a macro-reentry within the left fascicles. BBRT and interfascicular VT may also occur in the same patient. In contrast to the mentioned macro-reentry mechanisms there are focal Purkinje-related VTs arising from the anterior or posterior Purkinje system. Focal Purkinje triggered premature ventricular contractions originating from the distal Purkinje arborization in patients without a structural heart disease, as well as in patients with known ischemic heart disease or an underlying channelopathy such as Brugada syndrome may induce polymorphic VTs. Catheter ablation is an effective treatment option for both monomorphic as well as polymorphic Purkinje-related VTs, often resulting in noninducibility and freedom from VT recurrence. A systematic analysis of the surface ECG and the intracardiac electrograms is essential for successful ablation of these heterogeneous and potentially curable VTs.

Sudden Cardiac Death: Epidemiology, Mechanisms, and Therapy

Sudden cardiac death is a major public health problem affecting 500,000 patients annually in the United States alone. The major risk factor for sudden cardiac death is the presence of coronary artery disease, usually in the setting of reduced ejection fraction. Globally, the incidence is expected to rise sharply as the prevalence of coronary artery disease and heart failure continue to increase. However, sudden cardiac death is a heterogeneous condition and may be caused by acute ischemia, structural defects, myocardial scar, and/or genetic mutations. Sudden death may occur even in a grossly normal heart. Beta-blockers can reduce the risk of sudden cardiac death, while implantable cardioverter defibrillators are effective at terminating malignant arrhythmias. Ejection fraction remains the major criterion to stratify patients for defibrillator implantation but this strategy alone is insensitive and nonspecific. Novel clinical, electrophysiologic, and genetic markers have been identified that may increase precision in patient selection for primary prevention therapy. This review discusses the epidemiology, mechanisms, etiologies, therapies, treatment guidelines, and future directions in the management of sudden cardiac death.

Recurrent cardiac events in patients with idiopathic ventricular fibrillation, excluding patients with the Brugada syndrome

BACKGROUND

The recurrence of cardiac events in patients with idiopathic ventricular fibrillation (VF) excluding patients with the Brugada syndrome is unclear since this entity remains present in previous studies.

METHODS

Since 1992, 18 patients (72% male) with idiopathic VF out of 455 ICD implants were treated with an implantable cardioverter defibrillator (ICD). The mean age at first ICD implantation was 42 +/- 14 years. Brugada syndrome, as well as other primary electrical diseases (e.g. long QT), were systematically excluded in all patients by the absence of the typical electrocardiogram (ST elevation in the right precordial leads) at rest and/or after pharmacological tests (ajmaline, flecainide, or procainamide). Recurrence of cardiac events was prospectively assessed.

RESULTS

During a mean follow-up period of 41 +/- 27 months, VF recurrence with appropriate shock occurred in 7 patients (39%) covering a total of 27 shocks. The median time to first appropriate shock was 12 +/- 9 months. There were no deaths. In the electrophysiological study, 39% of patients were inducible, but inducibility failed to predict subsequent arrhythmic events. Forty-four percent of patients suffered 21 inappropriate shocks, which were caused by sinus tachycardia, atrial arrhythmias or lead malfunction.

CONCLUSION

Idiopathic ventricular fibrillation patients have a high recurrence rate of potentially fatal ventricular arrhythmias, excluding patients with the Brugada syndrome or other known causes. ICD prevents sudden cardiac death but inappropriate shocks remained a major issue in this young and active population.

A 25-year control of idiopathic ventricular fibrillation with electrophysiologic-guided antiarrhythmic drug therapy

The case of a 28-year-old man with recurrent syncope and multiple documented episodes of idiopathic ventricular fibrillation is reported. Recurrent syncope suggesting a self-terminating ventricular tachyarrhythmia occurred after 1 month of amiodarone therapy, and ventricular fibrillation was inducible at electrophysiologic study. After addition of quinidine, no significant ventricular arrhythmias could be induced. Similar results were found during a repeat electrophysiologic study performed 23.5 years later. During a 25-year period, the patient has remained arrhythmia-free on combined antiarrhythmic medication with quinidine and amiodarone.

Lower Observed Versus Expected (Based on U.S. Age and Gender Specific Rates) Survival in Patients Treated for Near-Fatal Ventricular Arrhythmias

Implantable cardioverter defibrillators (ICDs) have improved survival for patients with ventricular fibrillation (VF) or sustained vertricular tachycardia (VT). However, the survival of these patients compared to the general population has not been assessed. Observed survival rates for patients randomized to either antiarrhythmic drug therapy (mainly amiodarone) arm or ICD arm were compared to expected rates, calculated using age and sex-specific survival rates derived from the 1989-1991 US population life tables and applied to the age and sex distribution of patients in each arm. Consistent with the results of the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, patients randomized to receive ICDs experienced significantly higher survival than those in the drug arm; however, both groups experienced significantly lower survival than expected using age and gender matched U.S. survival rates. Within arms, the difference between the observed and expected rates increased over 3 years of follow-up from 7.7% to 15.3% for the ICD arm, and from 14.6% to 26.4% for the drug arm. These results quantify the improvements in survival that can be expected for VF or VT patients using drug or ICD therapies and underscore the need for continued research into methods for further improving the overall level of health of these patients.

Sudden cardiac death in 15-35-year olds in Sweden during 1992-99

OBJECTIVES

To study the incidence, pathogenesis and symptoms preceding sudden cardiovascular death amongst 15-35-year olds without substance abuse in Sweden during 1992-99.

DESIGN

This was a register study of a national database of forensic medicine, Rattsbase. Clinical details were obtained from forensic, police and medical records and from interviews with family members.

SETTING

The whole nation of Sweden.

SUBJECTS

Individuals having suffered a sudden cardiac death.

RESULTS

We found 181 cases of sudden cardiovascular death in a nationwide database, Rattsbase, in 15-35-year olds, of which 132 (73%) were male and 49 (27%) were female, and a rather stable incidence of 0.93 per 100,000 per year. Preceding symptoms were seen in half of the cases. The most common forensic diagnoses were: no structural abnormality (21.0%), coronary atherosclerosis (17.7%), dilated cardiomyopathy (12.2%), hypertrophic cardiomyopathy (10.5%) and myocarditis (10.5%).

CONCLUSION

Sudden cardiovascular death was uncommon in the young, but the incidence was not decreasing. Postmortem diagnoses were often difficult to establish. There was a high frequency of structurally normal hearts. Because premortal cardiac-related symptoms are relatively common and treatment methods are developing, we should learn to recognize early symptoms of heart disease. To identify individuals at risk, further studies of preceding symptoms, life-style factors and electrocardiogram (ECG) changes are needed.

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.

Mode of onset of ventricular fibrillation in patients with Brugada syndrome detected by implantable cardioverter defibrillator therapy

OBJECTIVES

We sought to demonstrate the mode of spontaneous onset of ventricular fibrillation (VF) in patients with Brugada syndrome.

BACKGROUND

The electrophysiologic mechanisms of VF in Brugada syndrome have not been fully investigated.

METHODS

Nineteen patients (all male, mean age 47 +/- 12 years) with Brugada syndrome were treated with an implantable cardioverter defibrillator (ICD). The implanted devices were capable of storing electrograms during an arrhythmic event. We investigated the mode of spontaneous onset of VF according to the electrocardiographic features during the episode of VF, which were obtained from stored electrograms of ICDs and/or electrocardiographic (ECG) monitoring.

RESULTS

During a follow-up of 34.7 +/- 19.4 months (range 14 to 81 months), 46 episodes of spontaneous VF attacks were documented in 7/19 (37%) patients. The event-free period between ICD implantation and the first spontaneous occurrence of VF was 14.6 +/- 12.1 months (range 3.7 to 27.4 months). We investigated 33/46 episodes of VF, for which electrocardiographic features (10 to 20 s before and during VF) were obtained from ICDs and/or ECG monitoring in five patients. A total of 22/33 episodes of VF were preceded by premature ventricular contractions (PVCs), which were almost identical to the initiating PVCs of VF. Furthermore, in three patients who had multiple VF episodes, VF attacks were always initiated by the same respective PVC. The coupling interval of the initiating PVCs of VF was 388 +/- 28 ms.

CONCLUSIONS

Spontaneous episodes of VF in patients with Brugada syndrome were triggered by specific PVCs. These findings may provide important insights into the pathophysiological mechanisms causing VF in Brugada syndrome.

Advantages and disadvantages of trial designs: a review of analysis methods for ICD studies. AVID Investigators

General modalities of analyses that have been used for ICD studies are reviewed. Published "typical" examples are briefly described. The historical cohort method is exemplified with previously unpublished data from the Seattle Cardiac Arrest Survivor database. The AVID Study database is used to compare the results obtained from nonrandomized methodologies with randomized methodologies. Particular issues related to the use of the ICD for example, mode of death, inability to blind, selection practice, and treatment decision times make this a natural pedagogic platform.

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.

Effects of electrophysiologic-guided therapy with Class IA antiarrhythmic drugs on the long-term outcome of patients with idiopathic ventricular fibrillation with or without the Brugada syndrome

INTRODUCTION

Implantation of a implantable cardioverter defibrillator (ICD) is viewed universally as the "gold standard" therapy for patients with idiopathic ventricular fibrillation (VF). We sought to study the long-term value of electrophysiologic (EP)-guided therapy with Class IA antiarrhythmic drugs in patients with idiopathic VF with or without the Brugada syndrome.

METHODS AND RESULTS

We performed EP studies in 34 consecutive patients who had idiopathic VF with (n = 5) or without (n = 29) the Brugada syndrome. All patients with inducible sustained polymorphic ventricular tachycardia (SPVT) or VF underwent repeated EP evaluation after oral administration of a Class IA antiarrhythmic drug (mainly quinidine). Patients rendered noninducible received this therapy on a long-term basis. SPVT/VF were induced in 27 (79.4%) patients at baseline studies. Class IA drugs effectively prevented induction of SPVT/VF in 26 (96%) patients. Of the 23 patients treated with these medications, no patient died or had a sustained ventricular arrhythmia during a mean follow-up period of 9.1 +/- 5.6 years (7 to 20 years in 15 patients). Two deaths occurred in patients without inducible SPVT/VF at baseline studies who had been treated empirically.

CONCLUSION

Our results suggest that EP-guided therapy with Class IA agents is a reasonable, safe, and effective approach for the long-term management of patients with idiopathic VF. A randomized prospective study of EP-guided Class IA therapy in patients with ICDs seems warranted.

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.

[Ventricular fibrillation and myocarditis]

We report a case of ventricular fibrillation with subacute myocarditis as the only underlying pathological abnormality in a 9-year-old child. The patient died suddenly after a follow-up of 13 years, despite the apparent control of the arrhythmia.

Polymorphic ventricular tachyarrhythmias in the absence of organic heart disease: classification, differential diagnosis, and implications for therapy

Different polymorphic ventricular tachyarrhythmias may cause syncope or cardiac arrest in patients with no heart disease: (1) Catecholamine-sensitive polymorphic ventricular tachycardia (VT) presents during childhood: the hallmark is the reproducible provocation of atrial and polymorphic ventricular arrhythmias during exercise, despite a normal QT. Beta-blockers are the treatment of choice. (2) In the long QT syndromes (LQTS), malfunction of ion channels leads to prolonged ventricular repolarization, early afterdepolarizations, and triggered ventricular arrhythmias. Therapeutic options include: beta-blockers, genotype-specific therapy, cardiac sympathetic denervation, and implantation of pacemakers or defibrillators. (3) The "short-coupled variant of torsade de pointes" is a malignant disease that shares several characteristics with idiopathic ventricular fibrillation. Although verapamil is frequently recommended, mortality rates remain high. (4) Idiopathic ventricular fibrillation (VF) with normal electrocardiogram (ECG) strikes young adults of both genders. In contrast to other polymorphic tachyarrhythmias, idiopathic VF is not generally related to stress. Also, familial involvement is rare. Therapeutic options include implantation of defibrillators and therapy with class 1A drugs. (5) The "Brugada syndrome" and the "syndrome of nocturnal sudden death" strike males almost exclusively. Right bundle branch block (RBBB) with ST elevation in the right precordial leads-the "Brugada sign"--is seen in the ECG of both patient populations. Implantation of defibrillators is recommended.

Late outcome of survivors of idiopathic ventricular fibrillation

This report describes clinical, hemodynamic, and electrophysiologic characteristics of 18 consecutive survivors of sudden cardiac arrest due to idiopathic ventricular fibrillation (VF) between 1986 and 1996. Long-term data in relation to the prescribed therapy are presented. The mean age of the 18 patients was 48 +/- 14 years (median 49). Electrophysiologic studies showed a low inducibility of sustained ventricular tachyarrhythmias in 4 patients (22%). Treatment consisted of class III agents, beta blockers, or implantable cardioverter-defibrillators. Two patients were discharged without any therapy. Therapy control was undertaken either by serial drug testing or by the empirical approach. Serious complications of therapy occurred in 2 patients: 1 patient experienced a proarrhythmic effect of antiarrhythmic drug therapy, and the other patient received multiple inadequate defibrillator discharges due to a defect in the transvenous lead. All but 1 patient (94%) remained free of recurrences of sudden cardiac arrest during a follow-up time of 45 +/- 29 months (median 41). One patient died 2 weeks after surviving cardiac arrest due to intractable VF while receiving sotalol treatment. Therapy guided by electrophysiologic studies did not have any impact on survival. Adverse effects or noncompliance led to discontinuation of drug therapy in 7 patients after a mean period of 31 +/- 30 months. Without any treatment 9 patients remained without recurrences over 45 +/- 33 months. Because of the absence of risk factors for arrhythmia recurrence and criteria to select therapy, randomized prospective studies are warranted to assess the optimal therapies in these young, ostensibly healthy patients.

Idiopathic ventricular fibrillation: clinical, electrophysiologic characteristics and long-term outcomes

The long-term prognosis, including risks of arrhythmic recurrence of idiopathic ventricular fibrillation (VF), is uncertain; moreover, the role of electrophysiologic study in the diagnosis and guiding of antiarrhythmic drugs therapy for idiopathic VF remains controversial. The purpose of this study was to study the clinical features, electrophysiologic characteristics and long-term clinical outcomes of six consecutive patients (five males) who had at least one episode of aborted cardiac arrest (5 patients) or syncope (1 patients) with documentation of ventricular fibrillation (VF) in the absence of apparent heart disease. Idiopathic VF was diagnosed by exclusion. All patients underwent the electrophysiologic study including intravenous antiarrhythmic drug testing. Recurrences of VF after therapy and the long-term outcomes were assessed. The mean age at the first episode was 43+/-19 years (range from 16 to 63 years). All patients had sustained VF induced by double (3 patients) or triple (3 patients) ventricular extrastimuli at a paced cycle length of 400 or 500 ms from the right ventricular apex. Intravenous procainamide and/or mexiletine could suppress the reinduction of sustained VF in 4 (67%) of 6 patients. Recurrence of VF (documented VF attack, sudden cardiac arrest or syncope) was observed in 3 (100%) of 3 patients who received procainamide or mexiletine alone. Four patients (including 3 patients who experienced recurrence) received amiodarone alone or in combination with mexiletine, and these drugs could effectively prevent recurrence of VF. One patient with exercise-induced VF remained asymptomatic without any treatment during a follow-up period of 95 months. Another patient received an implantable cardioverter-defibrillator without concomitant antiarrhythmic drug therapy and had no discharge of electrical shock during 28 months of follow-up. During a mean follow-up period of 64+/-40 months (range from 28 to 128 months), all the patients were alive except patient No. 2 who died of acute hepatic failure. In conclusion, electrophysiologic study is a reliable diagnostic method, but it was of limited value in guiding antiarrhythmic drug therapy for preventing recurrence of idiopathic VF. Class I drug alone was associated with a high recurrence rate (100%) despite predictions that it would be effective by the electrophysiologic study. Amiodarone alone or in combination with mexiletine effectively prevented the recurrence of VF during the long-term follow-up along with a favourable outcome.

Implantable cardioverter defibrillator utilization among device recipients presenting exclusively with syncope or near-syncope

INTRODUCTION

Implantable cardioverter defibrillators (ICDs) are occasionally used in presumed high-risk patients with electrocardiographically undocumented syncope, although the incidence of ventricular tachyarrhythmias in this population is not well defined.

METHODS AND RESULTS

We studied 33 consecutive patients receiving an ICD (67% nonthoracotomy and 70% tiered therapy) after electrophysiologic testing for unmonitored "syncope" (n = 29) or "near-syncope" (n = 4). Atherosclerotic heart disease was present in 24 (73%); mean left ventricular ejection fraction (LVEF) was 0.39 +/- 0.15; and sustained monomorphic ventricular tachycardia (SMVT) was inducible in 18 (55%). Over a median follow-up of 17 months (range 4 to 61), 12 patients (36%) received > or = 1 appropriate ICD discharge triggered by SMVT (cycle length 230 to 375 msec) in 10 and ventricular flutter or fibrillation in 2--without concomitant antiarrhythmic medication in 8 of 12 cases. Inducible SMVT and LVEF < or = 0.35 were statistically significant, independent predictors of an appropriate ICD discharge (P < 0.02 and P < 0.03, respectively). Estimated 1-year cumulative survival free of appropriate discharge was 34% versus 87%, respectively, in patients with versus without inducible SMVT (P < 0.02), and 18% versus 56%, respectively, in patients with LVEF < or = 0.35 versus LVEF > 0.35 (P < 0.03).

CONCLUSION

In this highly select, multicenter population of ICD recipients with electrocardiographically undocumented syncope, a substantial incidence of appropriate device discharges was observed, particularly in patients with inducible SMVT and LVEF < or = 0.35. These findings support the notion that, in patients with LV dysfunction and inducible SMVT, ventricular tachyarrhythmias are likely to account for episodes of syncope or near-syncope.

Ventricular arrhythmias in apparently healthy subjects

While it is assumed that the normal heart does not predispose to serious arrhythmias, several conditions are now being recognized as being associated with short-lasting ventricular arrhythmias. It also becomes clear that idiopathic VT (or repetitive monomorphic VT) sometimes exists on the background of a compromised heart. Whether this dysfunction is due to the arrhythmia or vice versa is not evident. Finally, VF occurs in patients who, at a first glance, have no apparent heart disease, and it is then called idiopathic VF. These complex electrical abnormalities probably reflect disorders, which often are genetically determined. Recognition of these syndromes, often characterized by abnormal repolarization or a disturbed autonomic function is possible if appropriate techniques are used.

Idiopathic ventricular fibrillation

Idiopathic ventricular fibrillation is defined as cardiac arrest in the absence of structural heart disease and other identifiable causes of ventricular fibrillation. It occurs in 1% to 9% of survivors of out-of-hospital cardiac arrest. The mean age of these patients is 35 to 40 years, and 70% to 75% are male. The pathogenesis is unknown; psychosocial factors may play a role. Baseline clinical characteristics have not been found to identify the 20% to 30% of patients who will have recurrent cardiac arrest. At present, implantation of an automatic defibrillator is the treatment of choice. Two registries have been established to enhance our knowledge of this unusual catastrophic entity.

Sudden cardiac death in persons with normal (or near normal) hearts

I have tried to provide a broad overview of the problem of cardiac arrest in the absence of structural heart disease or in the presence of minimal disease, as well as those disease states that are difficult to recognize. Exciting progress in this field has been made in recent years and I anticipate that we will continue to make progress in the future.

What to do in patients with no structural heart disease and sudden arrhythmic death?

The term "idiopathic" ventricular fibrillation is used to describe those episodes of unexpected sudden arrhythmic death due to ventricular fibrillation in patients with no demonstrable structural heart disease. Idiopathic ventricular fibrillation has been reported to account for 5-100% of all sudden arrhythmic deaths. Post mortem analysis have shown that about 80% of patients might have some kind of structural anomalies, mainly atherosclerosis, myocarditis, or right ventricular dysplasia. Follow-up of patients with idiopathic ventricular fibrillation has shown a high incidence of recurrent episodes of malignant ventricular arrhythmias. The absence of structural heart disease generally implies an excellent long-term prognosis if ventricular fibrillation can be avoided. Patients with an implantable defibrillator should have a mortality rate similar to the general population. New subsets of patients are being recognized as belonging with those previously classified as idiopathic ventricular fibrillation. More than 60 patients have been identified in different centers around the world with the so-called "right bundle branch block, ST segment elevation, and sudden death syndrome." Recurrence rate of malignant ventricular arrhythmias is very high in these patients, despite antiarrhythmic therapy. An implantable cardioverter-defibrillator seems the treatment of choice. Asymptomatic forms of the syndrome have been described. Follow-up in these asymptomatic patients has shown that some of them might become symptomatic during follow-up. Also, intermittent forms of the syndrome have been described, with transient normalization of the electrocardiogram. Administration of class I drugs in these patients unmasks the typical electrocardiographic pattern. In some of the patients previously classified as having idiopathic ventricular fibrillation, ajmaline or procainamide administration unmasks the electrocardiographic pattern of the syndrome, suggesting that its incidence may be higher than previously suspected.

Electrophysiological findings in idiopathic recurrent ventricular fibrillation: special reference to mode of induction, drug testing, and long-term outcomes

Electrophysiological studies can be useful in the presence of idiopathic ventricular fibrillation (VF) and may be used when selecting antiarrhythmic drugs. However, the yield, the mode, and the long-term reproducibility of the induction of VF have not yet been fully elucidated. Eight patients with idiopathic VF underwent electrophysiological study. The mean age (+/- SD) was 45 +/- 17 years. Six were males and two were females. Diagnosis was done by exclusion. VF was induced in 6 (75%) of 8 patients using double extra stimuli at coupling intervals of 233 +/- 39 and 191 +/- 20 ms for the first and second extra stimuli, respectively. Of note, VF was induced by stimulation exclusively at the origin of the premature ventricular beat, which was the first complex of VF in two patients. In another patient, VF was initiated by two premature stimuli and also by a pause produced by rapid pacing. The inducibility of VF was reproduced 9-18 months after the first induction in all of the four patients studied. When the ability of antiarrhythmic drugs to suppress VF inducibility was confirmed, no recurrence was observed during the follow-up period of 40-160 months, but a recurrence of VF was observed in one of two nonresponders. In one patient, amiodarone administration failed in preventing VF induction 9 months after initiation of therapy, and reassessment of long-term drug-efficacy might be indicated in some patients. In conclusion, idiopathic VF was highly inducible (75%) with double extra stimuli. In this study, it was induced from a specific site (2/8) or by a pause (1/8). Induction of VF seemed to be reproduced 9-18 months after the first study. The outcome was considered favorable when the inducibility of VF was suppressed by antiarrhythmic drugs.

Optimal defibrillation strategy and follow-up of out-of-hospital cardiac arrest. The Belgian CPCR Study Group

In the current climate of rising healthcare cost, resuscitation efforts performed outside the hospital are critically evaluated because of their limited success rate in some settings. As part of a quality assurance program between the 1st January 1991 and 31st December 1993, six centres of the Belgian CPCR study group prospectively registered cardiac arrest (CA) patients and their treatment according to the Ustein Style recommendations. In the group (n = 511) of patients initially found in ventricular fibrillation (VF) a significantly better survival rate was observed for those patients who received a 1st defibrillatory shock by the 1st tier (n = 142 (27.8%)) as compared to those defibrillated after arrival of the 2nd tier (n = 369 (72.2%)). Median time to delivery of the first shock was significantly shorter (5 min) in the 1st tier group. In a second part of the study we describe long-term management of the 28 surviving VF patients, treated by the single EMS system of Brugge between 1st January 1991 and 30th April 1995: only 6 patients eventually received an implantable cardioverter defibrillator (ICD), whereas coronary revascularization was performed in 9 patients, and 3 patients were discharged on amiodarone only. Satisfactory long-term survival after out-of-hospital VF can be achieved by an early shock followed by advanced life support and appropriate definitive treatment.

Favourable outcome in idiopathic ventricular fibrillation with treatment aimed at prevention of high sympathetic tone and suppression of inducible arrhythmias

OBJECTIVE

In the absence of an obvious cause for cardiac arrest, patients with idiopathic ventricular fibrillation are difficult to manage. A subset of patients has inducible arrhythmias. In others sympathetic excitation plays a role in the onset of the cardiac arrest. This study evaluates a prospective stepped care approach in the management of idiopathic ventricular fibrillation, with therapy first directed at induced arrhythmias and secondly at adrenergic trigger events.

SETTING

University Hospital.

PATIENTS

10 consecutive patients successfully resuscitated from idiopathic ventricular fibrillation.

INTERVENTIONS

Programmed electrical stimulation to determine inducibility, followed by serial drug treatment. Assessment of pre-arrest physical activity and mental stress status by interview, followed by beta blockade. Cardioverter-defibrillator implantation in non-inducible patients not showing significant arrest related sympathetic excitation.

MAIN OUTCOME MEASURE

Recurrent cardiac arrest or ventricular tachycardia.

RESULTS

Five patients were managed with serial drug treatment and four with beta blockade. In one patient a defibrillator was implanted. During a median follow up of 2.8 years (range 6 to 112 months) no patient died or experienced defibrillator shocks. One patient had a recurrence of a well tolerated ventricular tachycardia on disopyramide.

CONCLUSIONS

Idiopathic ventricular fibrillation may be related to enhanced sympathetic activation. Prognosis may be favourable irrespective of the method of treatment. Whether the present approach enhances prognosis of idiopathic ventricular fibrillation remains to be determined. However, it may help to avoid potentially hazardous antiarrhythmic drugs or obviate the need for implantation of cardioverter-defibrillators.