Determinants of prognosis in idiopathic dilated cardiomyopathy as determined by programmed electrical stimulation

Epicardial Ablation of VT in Patients with Nonischemic LV Cardiomyopathy

The past decade has seen a remarkable period of discovery and refinement of ventricular tachycardia (VT) ablation in patients with left ventricular cardiomyopathy (LVCM). Patients with LVCM presenting with VT have a common substrate distribution involving predominantly the basal or perivalvular LV, which is often more dramatic on the LV epicardium. They typically present with multiple and often unstable tachycardias due to scar-based reentry. Percutaneous intrapericardial access can be safely performed in the electrophysiology laboratory and has greatly enhanced the efficacy of VT ablation in this setting by allowing detailed mapping. Epicardial ablation incurs unique procedural considerations that must be understood to safely and effectively perform the procedure.

[Limits and scopes of invasive risk stratification. Do we still need programmed ventricular stimulation?]

Patients with ischemic heart disease and left ventricular systolic dysfunction (ICM), dilated (DCM), hypertrophic (HCM), or arrhythmogenic right ventricular cardiomyopathy (ARVCM) carry a high risk of sudden cardiac death (SCD). Ventricular tachyarrhythmias are most often the cause of SCD, which can be treated with internal cardioverter defibrillators (ICDs). However, a great proportion of these high-risk patients will never experience potentially lethal ventricular arrhythmias, and as such will never be in need of these devices. Given the risks, inconvenience, and costs of ICDs, markers that adequately stratify patients according to their risk of SCD are needed. Programmed ventricular stimulation (PVS) has long been used to identify the patients' risk of SCD. However, the prognostic ability of PVS is only modest and the negative predictive value is poor. As far as patients with ICM are concerned, recent data from the MUSTT and MADIT II trials demonstrate that in patients with a left ventricular ejection fraction between 30% and 40%, inducibility by PVS can help to identify patients who are at particularly increased risk of SCD. The value of PVS in patients with DCM, HCM, and ARVCM for risk stratification of SCD is less clear and the available data even more limited. In these patients, the inducibility of ventricular tachyarrhythmias does not clearly correlate with VT/VF (ventricular tachycardia/ventricular fibrillation) risk, and more importantly, noninducibility does not portend good prognosis. The current German guidelines appreciate these uncertainties of PVS for risk stratification with class IIb recommendations in certain patients with ICM, HCM or ARVCM. In the future, combining the results of invasive PVS with other noninvasive parameters may improve its prognostic value. Furthermore, expanding the role of PVS to guiding therapeutic ablation of ventricular arrhythmias may influence patient's future risk of SCD.

Sudden death in dilated cardiomyopathy

The purpose of this review is to examine the potential contribution of arrhythmia to the occurrence of sudden death in dilated cardiomyopathy (DCM) and to discuss current treatment options. We performed a search of the MEDLINE database from 1985 to the present and the reference citations of selected articles pertaining to the prognostic significance, management, and pathophysiology of arrhythmias in DCM. A large proportion of patients with DCM die suddenly, most secondary to ventricular arrhythmia and a smaller proportion due to bradyarrhythmia. The presence and severity of ventricular ectopy may predict risk for sudden death, but the role of electrophysiologic study and signal-averaged electrocardiography in further risk stratifying patients remains uncertain. Abnormalities of the autonomic nervous system and renin-angiotensin-aldosterone axis appear to promote the occurrence of ventricular arrhythmias. Angiotensin-converting enzyme inhibitors improve overall mortality in congestive heart failure, and the use of direct angiotensin-receptor antagonists is currently being studied. In addition, beta-receptor antagonists appear to improve morbidity and may prove to improve mortality in heart failure as well. Other interventions still under investigation include amiodarone and the implantable cardioverter-defibrillator. The underlying pathophysiology of sudden death in DCM involves primarily ventricular tachyarrhythmia. Angiotensin-converting enzyme inhibitors remain a mainstay of improving overall mortality, while further study on the roles for newer drugs and devices is ongoing.

Sudden cardiac death: the role of risk stratification

Sudden cardiac death syndrome remains a major health problem responsible for approximately 400,000 deaths annually in the US. Effective therapies exist but are costly and are associated with potential complications. Currently used strategies for selection of the best candidates for implantable cardioverter defibrillator (ICD) therapy are imperfect and leave a large number of high-risk patients unprotected. At the same time, many patients who received ICDs will never develop tachyarrhythmia and require ICD intervention. The article summarizes the current status and applicability of the noninvasive and invasive tests used for sudden cardiac death risk assessment with the emphasis on the increasingly recognized value of microvolt T wave alternans.

Primary Prophylaxis of Sudden Death in Hypertrophic Cardiomyopathy, Arrhythmogenic Right Ventricular Cardiomyopathy, and Dilated Cardiomyopathy

We present an evidence-based overview of primary prevention of sudden cardiac death. Several recent studies have provided important data regarding pharmacologic and device-based therapy for patients with conditions that confer high risk for sudden death. A rational approach to these therapies, with emphasis on implanted cardiovertor defibrillators, is discussed.

Programmed ventricular stimulation in patients with idiopathic dilated cardiomyopathy and syncope receiving implantable cardioverter-defibrillators: a case series and a systematic review of the literature

BACKGROUND

The role of programmed ventricular stimulation (PVS) in patients with idiopathic dilated cardiomyopathy (DCM) and syncope receiving implantable cardioverter-defibrillators (ICD) remains controversial.

METHODS AND RESULTS

Between 1994 and July 2002, 20 patients with DCM and syncope underwent PVS and ICD implantation at the Onassis Cardiac Surgery Center or the Alexandra General Hospital. At PVS 10 patients had inducible sustained monomorphic ventricular tachycardia (SMVT), 3 patients had inducible sustained polymorphic ventricular tachycardia or ventricular fibrillation, and 7 patients had no inducible arrhythmia. The latter 7 patients received an ICD because of clinical occurrence of ventricular tachycardia (n=5) or fibrillation (n=2). Mean age was 55+/-14 years; 80% were men. During a mean follow-up of 2.8+/-2.3 years, 12 of the 20 patients received an appropriate shock. The incidence of appropriate shocks at 1 and 3 years was 69% and 84% in the inducible SMVT group, and 56% and 67% in the group without inducible SMVT (p=0.93, log rank test). Overall survival was similar in both groups (p=0.53). In a systematic review of the published literature 18 of 75 (24%) patients with DCM, syncope and a negative PVS had an appropriate ICD shock after a mean follow-up of 27 months.

CONCLUSION

PVS has a limited role in risk stratification of patients with DCM and syncope.

Prevalence and incidence of arrhythmias and sudden death in heart failure

Patients with heart failure are prone to a variety of arrhythmias, symptomatic and asymptomatic, that are prognostically significant and have an important bearing on the management of these patients. However there are some inherent problems in assessing the frequency of these arrhythmias within a large patient population, due to a lack of uniformity in defining heart failure and the transient nature of these rhythms. Patients with heart failure commonly die suddenly. The causes of these deaths are difficult to ascertain accurately and are often presumed arrhythmic. With the advent of effective interventions to prevent sudden death, accurately defining the causal relationship between the arrhythmias and sudden death has assumed great importance to appropriately target therapy. Several attempts have been made to predict such deaths on the basis of non-invasive and invasive diagnostic investigations with variable success. In this article we review the incidence and prevalence of atrial and ventricular arrhythmias and sudden deaths in epidemiological studies, surveys and randomised control trials of patients with heart failure. We discuss the prognostic significance of these arrhythmias, the inherent problems in their diagnosis and whether their presence predicts the risk of sudden deaths and the mode of such deaths in the heart failure population. The role of various investigations in risk stratification of sudden death has also been discussed.

Therapeutic options in patients with reduced ejection fraction and nonsustained ventricular tachycardia

The patient with a reduced ejection fraction and nonsustained ventricular tachycardia represents a common management problem for the physician. This article reviews the supporting evidence for the therapeutic options available for these patients according to the etiology of the reduced ejection fraction. In postinfarction patients, electrophysiology-guided implantable cardioverter defibrillator therapy improves survival more than antiarrhythmic therapy. In patients with nonischemic cardiomyopathy, the best therapy is yet undetermined. Ongoing clinical trials will hopefully direct future therapy.

Prognostic value of an abnormal signal-averaged electrocardiogram in patients with nonischemic dilated cardiomyopathy

The usefulness of an abnormal signal-averaged ECG (SAECG) for the risk stratification of patients with dilated cardiomyopathy was studied prospectively in 76 patients. Multiple analysis showed that an abnormal SAECG predicted cardiac mortality (p = 0.0046), sudden cardiac death, and the need for resuscitation (p = 0.003); however, it did not predict death from heart failure and heart transplantation.

Nonsustained ventricular tachycardia. A guide to the clinical significance and management

The patient with nonsustained ventricular tachycardia represents a common management problem for the cardiologists and internists. Treatment is sometimes needed for the suppression of symptoms. More commonly, nonsustained ventricular tachycardia is asymptomatic, and the clinician must determine the prognostic importance. The prognostic implications, the role of electrophysiologic study, and the potential role of pharmacologic and defibrillator intervention depend on the underlying cardiac substrate present in the individual patient.

Should stimulation therapy for congestive heart failure be combined with defibrillation backup?

Biventricular pacing has been proposed to resynchronize ventricular contraction in patients with congestive heart failure (CHF) and interventricular conduction delay. However, the sudden death rate is still high despite the improvement in cardiac performance. Devices combining biventricular pacing with implantable cardioverter defibrillator (ICD) backup are now under clinical investigation to demonstrate whether they can decrease sudden death. From the first implant of an ICD with biventricular transvenous pacing on August 1998 to April 2000, 96 patients underwent such implants: 67 (70%) received pacemakers alone and 29 (30%), who had class I ICD indications, received combined pacemaker/ICD systems. During a mean follow-up of 283 +/- 170 days, 13 (14%) patients died: 5 of 29 (17%) in the ICD group and 8 of 67 (12%) in the pacemaker group. A total of 15 patients (52%) had ICD shocks and 6 patients (21%) had 113 episodes of ventricular tachyarrhythmias, of which 96 (85%) were converted to sinus rhythm with antitachypacing. The echocardiograms showed a narrowing of the delay between the onset of right and left ventricular outflow from 40 +/- 37 msec to 17 +/- 16 msec (p = 0.03) and a reduction of the mitral regurgitation area from 7 +/- 3.8 cm2 to 5 +/- 4 cm2 (p = 0.04) at 3 months. Functional class improved from 2.8 +/- 0.7 to 1.6 +/- 0.5 (p <0.001) 3 months after implant. Thus, ischemic patients with reduced left ventricular ejection fraction and ventricular tachyarrhythmias seem good candidates for biventricular pacing with ICD backup. The sudden death risk for those with idiopathic dilated cardiomyopathy, however, is difficult to stratify, and the choice of ICD backup has to be considered on the basis of patient safety, as well as of costs.

Electrophysiologic testing to identify patients with coronary artery disease who are at risk for sudden death. Multicenter Unsustained Tachycardia Trial Investigators

BACKGROUND

The mortality rate among patients with coronary artery disease, abnormal ventricular function, and unsustained ventricular tachycardia is high. The usefulness of electrophysiologic testing for risk stratification in these patients is unclear.

METHODS

We performed electrophysiologic testing in patients who had coronary artery disease, a left ventricular ejection fraction of 40 percent or less, and asymptomatic, unsustained ventricular tachycardia. Patients in whom sustained ventricular tachyarrhythmias could be induced were randomly assigned to receive either antiarrhythmic therapy guided by electrophysiologic testing or no antiarrhythmic therapy. The primary end point was cardiac arrest or death from arrhythmia. Patients without inducible tachyarrhythmias were followed in a registry. We compared the outcomes of 1397 patients in the registry with those of 353 patients with inducible tachyarrhythmias who were randomly assigned to receive no antiarrhythmic therapy in order to assess the prognostic value of electrophysiologic testing.

RESULTS

Patients were followed for a median of 39 months. In a Kaplan-Meier analysis, two-year and five-year rates of cardiac arrest or death due to arrhythmia were 12 and 24 percent, respectively, among the patients in the registry, as compared with 18 and 32 percent among the patients with inducible tachyarrhythmias who were assigned to no antiarrhythmic therapy (adjusted P<0.001). Overall mortality after five years was 48 percent among the patients with inducible tachyarrhythmias, as compared with 44 percent among the patients in the registry (adjusted P=0.005). Deaths among patients without inducible tachyarrhythmias were less likely to be classified as due to arrhythmia than those among patients with inducible tachyarrhythmias (45 and 54 percent, respectively; P=0.06).

CONCLUSIONS

Patients with coronary artery disease, left ventricular dysfunction, and asymptomatic, unsustained ventricular tachycardia in whom sustained ventricular tachyarrhythmias cannot be induced have a significantly lower risk of sudden death or cardiac arrest and lower overall mortality than similar patients with inducible sustained tachyarrhythmias.

Arrhythmias in heart failure: current concepts of mechanisms and therapy

About one half of deaths in patients with heart failure are sudden, mostly due to ventricular tachycardia (VT) degenerating to ventricular fibrillation or immediate ventricular fibrillation. In severe heart failure, sudden cardiac death also may occur due to bradyarrhythmias. Other dysrhythmias complicating heart failure include atrial and ventricular extrasystoles, atrial fibrillation (AF), and sustained and nonsustained ventricular tachyarrhythmias. The exact mechanism of the increased vulnerability to arrhythmias is not known. Depending on the etiology of heart failure, different preconditions, including ischemia or structural alterations such as fibrosis or myocardial scarring, may be prominent. Reentrant mechanisms around scar tissue, afterdepolarizations, and triggered activity due to changes in calcium metabolism significantly contribute to arrhythmogenesis. Furthermore, alterations in potassium currents leading to action potential prolongation and an increase in dispersion of repolarization play a significant role. Treatment of arrhythmias is necessary either because patients are symptomatic or to reduce the risk for sudden cardiac death. The individual history, left ventricular function, electrophysiologic testing, and the signal-averaged ECG give useful information for identifying patients at risk for sudden cardiac death. The implantable cardioverter defibrillator (ICD) has evolved as a promising therapy for life-threatening arrhythmias. A potential role may exist for antiarrhythmic drugs, mainly amiodarone. There is growing evidence that patients with sustained VT or a history of resuscitation have the best outcome with ICD therapy regardless of the degree of heart failure. Many of these patients require additional antiarrhythmic therapy because of AF or nonsustained VTs that may activate the device. Catheter ablation or map-guided endocardial resection are additional options in selected patients but seldom represent the only therapeutic strategy.

Programmed ventricular stimulation for arrhythmia risk prediction in patients with idiopathic dilated cardiomyopathy and nonsustained ventricular tachycardia

OBJECTIVES

This study investigated the role of programmed ventricular stimulation (PVS) for arrhythmia risk prediction in patients with idiopathic dilated cardiomyopathy (IDC) and spontaneous nonsustained ventricular tachycardia (VT).

BACKGROUND

Nonsustained VT in patients with IDC has been associated with a high incidence of sudden cardiac death.

METHODS

Over the course of 4 years, 34 patients with IDC, a left ventricular (LV) ejection fraction < or = 35%, and spontaneous nonsustained VT underwent PVS. All patients were prospectively followed for 24+/-13 months.

RESULTS

Sustained ventricular arrhythmias were induced in 13 patients (38%). Sustained monomorphic VT was induced in three patients (9%), and polymorphic VT or ventricular fibrillation (VF) in another 10 patients (29%). No sustained ventricular arrhythmia could be induced in 21 study patients (62%). Prophylactic implantation of third-generation defibrillators (ICDs) with electrogram storage capability was performed in all 13 patients with inducible sustained VT or VF, and in nine of 21 patients (43%) without inducible sustained VT or VF. There were no significant differences between the additional use of amiodarone, d,I-sotalol, and beta-blocker therapy during follow-up in patients with and without inducible VT or VF. During 24+/-13 months of follow-up, arrhythmic events were observed in nine patients (26%) including sudden cardiac deaths in two patients and ICD shocks for rapid VT or VF in seven patients. Arrhythmic events during follow-up occurred in four of 13 patients with inducible ventricular arrhythmias compared with five of 21 patients without inducible ventricular arrhythmias at PVS (31% vs. 24%, p=NS).

CONCLUSION

PVS does not appear to be helpful for arrhythmia risk stratification in patients with IDC, a left ventricular ejection fraction < or =35%, and spontaneous nonsustained VT. Due to the limited number of patients, however, the power of this study is too small to exclude moderately large differences in outcome between patients with IDC with and without inducible VT or VF.

The top ten fallacies of nonsustained ventricular tachycardia

Nonsustained ventricular tachycardia (NSVT) continues to remain a subject of controversy. This is true despite a wealth of epidemiologic and basic/clinical laboratory findings that have accumulated during the past 2 decades. However, these data not only generate the impetus to conduct further research, but also provide compelling arguments against continued adherence to time honored precepts about NSVT that evolved since the inception of the "PVC Hypothesis," although never substantiated by rigorous scientific inquiry. This paper discusses the "top ten" fallacies of NSVT and details the data that support abandonment of them.

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.

Repolarization alternans: techniques, mechanisms, and cardiac vulnerability

Sudden cardiac death continues to be the leading cause of mortality in developed countries. Electrical alternans of the ST segment and the T wave on the surface ECG as a noninvasive marker of patients at risk is a phenomenon that was initially observed early in this century and was seen then to be associated with cardiac rhythm disturbances. Substantial evidence indicates that T wave alternans (TWA) is related to myocardial ischemic as a harbinger of malignant ventricular arrhythmias because it reflects dispersion and heterogeneity of repolarization. Recent data have demonstrated a significant correlation between TWA and vulnerability to ventricular arrhythmias in individuals with or without organic heart disease, it also predicts the results of electrophysiological testing and arrhythmia-free survival in patients with a variety of cardiac diseases. This article reviews the historical background of TWA and discusses the early experimental and recent clinical evidence implying an integral link between TWA and ischemia-induced cardiac vulnerability.

Arrhythmia risk: electrophysiological studies and monophasic action potentials

Shortly after in the introduction of programmed electrical stimulation (PES) of the heart to study and localize cardiac arrhythmias in the intact human heart, the technique was used for risk stratification of the arrhythmia patient. Two decades later we have to conclude that especially in ventricular arrhythmias the technique of PES did not live up to our expectations and the left ventricular function is a better long-term predictor than the induction of ventricular arrhythmias or the ability to find an antiarrhythmic drug able to prevent the initiation of the classically documented ventricular arrhythmia. Another sobering finding came from the analysis of the characteristics of the patient dying suddenly out-of-hospital, which showed that most of those patients could not be classified before the event as being at high risk using noninvasive or invasive testing, not even in those with a previous cardiac history. Monomorphic action potential (MAP) recordings have been of importance in our understanding of torsade de pointe arrhythmias in congenital and acquired QT prolongation. A major problem in case of a less generalized electrophysiological abnormality is the identification of the appropriate place where to put the MAP-electrode.

QRS prolongation is associated with inducible ventricular tachycardia after repair of tetralogy of Fallot

Prolonged QRS duration on the electrocardiogram has been found to predict adverse arrhythmic events in patients late after repair of tetralogy of Fallot. Whether QRS duration can also predict inducible ventricular tachycardia (VT) at electrophysiologic study is unknown. Between 1984 and 1995 we studied 135 survivors of tetralogy of Fallot surgery whose age at surgery was 34 days to 37 years (3.7 +/- 3.9, median 2.5) and age at electrophysiologic study was 1.4 to 43 years (9.7 +/- 8.2, median 6.7). QRS duration was 80 to 240 ms (137 +/- 29) and > or = 180 ms in 9 patients. Sustained VT was induced in 22 patients (monomorphic in 17). Induced sustained monomorphic VT was related to QRS duration, right ventricular dimension, H-V interval, and presence of symptoms. QRS duration was also related to induced sustained monomorphic VT by multivariate analysis. QRS duration > or = 180 ms was 35% sensitive and 97% specific for induced sustained monomorphic VT. QRS duration was related to induced sustained monomorphic VT even when only asymptomatic patients were analyzed. A QRS duration > or = 180 ms was 100% sensitive and 96% specific for detecting clinical VT. Prolonged QRS duration on the electrocardiogram is associated with induced sustained monomorphic VT on electrophysiologic study. The finding of prolonged QRS duration should suggest the need for further testing to determine the risk of adverse arrhythmic events in patients after repair of tetralogy of Fallot, even if they are asymptomatic.

Therapy of ventricular tachycardia in patients with nonischemic cardiomyopathies

In patients with IDCM and sustained VT, every effort should be made to exclude bundle branch reentrant tachycardia. We strongly believe that this mechanism of VT remains underdiagnosed despite electrophysiologic evaluation. In appropriate candidates with cardiomyopathies and "nonbundle branch reentrant VT," ICD implantation is frequently the treatment of choice, especially if the clinical presentation is that of hemodynamic collapse, or there is significant left ventricular systolic dysfunction. The role of amiodarone versus ICD, especially for patients with well-tolerated VT and milder forms of cardiomyopathies, is yet to be defined.

Time-domain signal-averaged electrocardiogram in nonischemic ventricular tachycardia

The prevalence of late ventricular potentials (LVPs) detected by signal averaged ECG (SAECG) is variable in nonischemic heart diseases. In idiopathic dilated cardiomyopathy, the prevalence increases from about 25% to 70%-90% in cases of spontaneous sustained ventricular tachycardia (VT), is not significantly correlated with hemodynamic and Holter data, and has a good positive predictive value for induced and spontaneous sustained VT. However, its predictive value for cardiac death has not been established. In primary hypertrophic cardiomyopathy, LVPs are rare (about 10%), not correlated to hemodynamic data, enhanced in cases of spontaneous sustained VT (up to 77%), and have a good predictive value of induced VT. LVP-SAECG are frequent in arrhythmogenic right ventricular dysplasia (ARVD) (70%-80%). They can identify patients with VT and an unapparent or limited form of this disease, or ARVD with few ventricular arrhythmias. The prevalence (26%-37%) of LVPs in mitral valve prolapse is clearly higher than in normal individuals or in other valvular diseases and is enhanced in cases of spontaneous and induced VT. Its significance remains speculative. After surgical repair of tetralogy of Fallot, LVPs can identify a group of patients with higher probability of induced and spontaneous risk of VT. The usefulness and significance of LVPs in other nonischemic cardiac diseases have not to date been established. In "true" idiopathic VT, without proved structural cardiac disease, the prevalence of LVPs does not exceed that observed in normal individuals (0%-5%), but in "apparent" idiopathic VT the prevalence of LVPs rises to 20%-40%. In these latter cases more invasive techniques must be used to discover a limited form of myocardiopathy.

Effect of sustained load on dispersion of ventricular repolarization and conduction time in the isolated intact rabbit heart

INTRODUCTION

It is well known that myocardial stretch can elicit ventricular arrhythmias in experimental models. However, previous reports have predominantly documented stretch-induced arrhythmias during short, pulsatile stretch. The arrhythmogenic mechanism of sustained static stretch is incompletely understood.

METHODS AND RESULTS

To examine the influence of sustained load on several electrophysiologic parameters, a latex balloon was placed into the left ventricle of ten isolated Langendorff-perfused rabbit hearts and filled with a neutral volume of fluid. The heart was paced from a catheter inside the right ventricle (apicoseptal endocardial position), and the following parameters were studied during steady-state pacing with a cycle length of 500 msec (S1) and during extrastimulation (S2, base drive of 8 beats): monophasic action potential (MAP) durations at 90% repolarization (APD90) from 5 to 6 epicardial electrodes located on both ventricles and one right ventricular endocardial contact electrode; dispersion of APD90 (range of MAP durations from all electrodes); effective refractory period (ERP) and longest activation time (pacing stimulus to MAP upstroke). After baseline recordings, the balloon inside the left ventricle was filled with a volume of 1.0 mL of fluid by means of a servo-controlled pump. The ERP was significantly shortened from 198 +/- 9 msec at baseline to 183 +/- 8 msec during sustained load (P < 0.03). Similarly, the average APD90 was shortened from 180 +/- 5 msec at baseline to 175 +/- 6 msec during sustained load (P < 0.006) with steady-state pacing and from 178 +/- 6 msec to 170 +/- 8 msec during premature extrastimulation (P < 0.03). At the same time, dispersion of APD90 was increased from 27 +/- 5 msec to 38 +/- 6 msec (P < 0.002) during steady-state pacing and from 28 +/- 4 msec to 38 +/- 6 msec (P = 0.013) during premature extrastimulation. The longest activation time among all MAP recordings was increased from 39 +/- 2 msec to 43 +/- 3 msec (P = 0.003) during steady-state pacing and from 56 +/- 6 msec to 69 +/- 6 msec during premature extrastimulation (P < 0.003).

CONCLUSIONS

Sustained load shortens the ERP and the mean APD90, and at the same time increases dispersion of APD90 and prolongs activation times. These findings provide additional insight into the arrhythmogenic mechanisms of sustained mechanical load.

Prognosis of idiopathic dilated cardiomyopathy

Previous reports in referral populations have emphasized the poor prognosis of dilated cardiomyopathy. This study evaluated mortality and morbidity in patients presenting at a referral center between 1989 and 1993. One hundred seventy-two consecutive patients were studied. At presentation, 82 were in New York Heart Association functional class III/IV. Mean (+/- SD) left ventricular end-diastolic dimension was 69 +/- 11 mm, ejection fraction was 25 +/- 10%, VO2 max was 21 +/- 9 mL/min/kg, and sodium was 136 +/- 9 mM. Treatments included vasodilators (n = 157, 92%), anticoagulation (n = 50, 29%), amiodarone (n = 52, 30%), and cardiac defibrillator (n = 5, 3%). During the follow-up period (mean, 26 +/- 29 months), 16 patients died and 60 developed progressive heart failure; 46 (27%) required cardiac transplantation. The majority of the patients (102, 59%) were stable or improved. Established prognostic determinants (left ventricular end-diastolic dimension, ejection fraction, sodium, and arrhythmia) were of low predictive value for the development of progressive heart failure or sudden death. The 1- and 2-year probabilities of death or transplantation was 16 and 21%, respectively (death only 6 and 7%, respectively). These observations are subject to referral bias, but suggest that the majority of patients can remain stable. Any improvement in survival compared to earlier experience can be due to earlier diagnosis, availability of transplantation, and new heart failure management strategies.

Current approaches in patients with ventricular tachyarrhythmias

The article has summarized the studies and ongoing trials looking at the significance and treatment of ventricular tachyarrhythmias. In most instances, the presence of these arrhythmias is associated with an increased risk of future arrhythmic events. Electrophysiologic studies are helpful in risk stratification in patients with coronary artery disease but can be misleading in the setting of dilated cardiomyopathy and often produce nonspecific results in patients with HCM. The need for an invasive electrophysiologic study is crucial in the diagnosis of certain ventricular arrhythmias that are amenable to cure with radiofrequency catheter ablation, such as idiopathic ventricular tachycardia and BBR-VT. The correct approach for patients with SVT not amenable to catheter ablation remains to be determined. In deciding whether to use a device or drug therapy, however, one should take into consideration the degree of left ventricular dysfunction and the overall health status of the patient. For example, device implantation clearly reduces sudden death in patients with severe left ventricular dysfunction but may not change total mortality because these same patients may die of congestive heart failure. Device therapy might be more cost-effective for patients with less severe depression of left ventricular function.

Risk stratification for arrhythmic events in patients with nonischemic dilated cardiomyopathy and nonsustained ventricular tachycardia: role of programmed ventricular stimulation and the signal-averaged electrocardiogram

OBJECTIVES

This study investigated prediction of arrhythmic events by the signal-averaged electrocardiogram (ECG) and programmed stimulation in patients with nonischemic dilated cardiomyopathy.

BACKGROUND

Risk stratification in patients with nonischemic dilated cardiomyopathy remains controversial.

METHODS

Eighty patients with nonischemic dilated cardiomyopathy and spontaneous nonsustained ventricular tachycardia underwent signal-averaged electrocardiography (both time-domain and spectral turbulence analysis) and programmed stimulation. All patients were followed up for a mean of 22 +/- 26 months.

RESULTS

Sustained monomorphic ventricular tachycardia was induced in 10 patients (13%), who all received amiodarone. The remaining 70 patients were followed up without antiarrhythmic therapy. Of the 80 patients, 15% had abnormal findings on the time-domain signal-averaged ECG, and 39% had abnormal findings on spectral turbulence analysis. Time-domain signal-averaged electrocardiography had a better predictive accuracy for induced ventricular tachycardia than spectral turbulence analysis (88% vs. 66%, p < 0.01). During follow-up, there were 9 arrhythmic events (5 sudden deaths, 4 spontaneous ventricular tachycardia/fibrillation) and 10 nonsudden cardiac deaths. Cox regression analysis showed that no variables predicted arrhythmic events or total cardiac deaths. The 2-year actuarial survival free of arrhythmic events was similar in patients with or without abnormal findings on the signal-averaged ECG or induced ventricular tachycardia.

CONCLUSIONS

In patients with nonischemic dilated cardiomyopathy, 1) there is a strong correlation between abnormal findings on the time-domain signal-averaged ECG and induced ventricular tachycardia, but both findings are uncommon; and 2) normal findings on the signal-averaged ECG, as well as failure to induce ventricular tachycardia, do not imply a benign outcome.

Sudden cardiac death in heart failure. The role of abnormal repolarization

Congestive heart failure is a common, highly lethal cardiovascular disorder claiming over 200,000 lives a year in the United States alone. Some 50% of the deaths in heart failure patients are sudden, and most of these are probably the result of ventricular tachyarrhythmias. Methods designed to identify patients at risk have been remarkably unrewarding, as have attempts to intervene and prevent sudden death in these patients. The failure to impact favorably on the incidence of sudden death in heart failure patients stems largely from a lack of understanding of the underlying mechanisms of arrhythmogenesis. This article explores the role of abnormalities of ventricular repolarization in heart failure patients. We will examine evidence for the hypothesis that alteration of repolarizing K+ channel expression in failing myocardium predisposes to abnormalities in repolarization that are arrhythmogenic. The possible utility of novel electrophysiological and ECG measures of altered ventricular repolarization will be explored. Understanding the mechanism of sudden death in heart failure may lead to effective therapy and more accurate identification of patients at greatest risk.

Serial evaluation of dilated cardiomyopathy with exercise thallium-201 tomography: correlation with the evolution of left ventricular parameters

The purpose of this prospective study was to correlate (1) the initial findings of exercise thallium-201 tomography with the evolution of left ventricular parameters at long term follow-up in patients with dilated cardiomyopathy and (2) the changes of exercise thallium-201 tomography repeated 1 year later. We studied 19 men with dilated cardiomyopathy and normal coronary angiogram. Two patients died and three patients had heart transplantation during follow-up. The other 14 patients were assessed at baseline and 1-year follow-up. Thallium-201 tomograms were divided into 20 segments for each patient. Two groups were defined according to the evolution of left ventricular ejection fraction: group 1 (n = 7) had unchanged or decreased ejection fraction at follow-up (24 +/- 11% at baseline versus 22 +/- 11% at follow-up, ns) and group 2 (n = 7) had improved ejection fraction at follow-up (25 +/- 9% at baseline versus 49 +/- 8% at follow-up, P < 0.03). The number of total abnormal segments at stress were not statistically different at baseline between groups 1 and 2, and in group 1 between baseline and follow-up. Group 2 at follow-up had a reduced number of total abnormal segments (P < 0.03). The percentage of reversibility was similar in both groups at baseline and follow-up. On exercise thallium-201 tomography, neither the presence nor the reversibility of stress myocardial perfusion abnormalities can predict improvement of left ventricular ejection fraction in dilated cardiomyopathy. However, regression of dilated cardiomyopathy is accompanied by a reduction of stress myocardial perfusion abnormalities.

Incidence and prediction of induced ventricular tachyarrhythmias in idiopathic dilated cardiomyopathy

The value of time-domain and spectral turbulence analyses of the signal-averaged electrocardiogram (SAECG) for predicting induction of sustained monomorphic ventricular tachycardia (VT) was prospectively investigated in 70 patients with idiopathic dilated cardiomyopathy. Sustained VT was induced in 9 patients (13%). The prevalence of abnormal time-domain and spectral analyses was 16 and 37%, respectively. The total predictive accuracy of time-domain and spectral analyses for VT induction was 86 and 67%, respectively (p < 0.01). The predictive accuracy of time-domain and spectral analysis was similar in patients without an intraventricular conduction defect (94 and 84%, respectively). However, the predictive accuracy of time-domain was higher than that of spectral analysis in patients with an intraventricular conduction defect (65 vs 25%; p < 0.05). The poor concordance between spectral analysis and programmed stimulation results was mainly due to the high number of false-positive recordings in the presence of an intraventricular conduction defect (9 of 20 cases). With the use of stepwise discriminant function analysis, an abnormal time-domain SAECG was the only variable predicting the induction of sustained VT (p < 0.0003). In dilated cardiomyopathy, an abnormal time-domain SAECG and induced sustained VT are rare, both time-domain signal-averaged electrocardiography and spectral analysis have a high predictive accuracy for VT induction in patients without an intraventricular conduction defect, and spectral analysis does not improve VT prediction in those with a conduction defect.

The role of implantable cardioverter defibrillators in dilated cardiomyopathy

Depending on the severity of the disease, patients with dilative cardiomyopathy (DCM) have a poor prognosis. No definite data are available to show that complex ventricular ectopy, the presence of ventricular late potentials, or programmed electrical stimulation in patients without symptoms with DCM identify patients at risk of sudden cardiac death. Although poor left ventricular function seems to be the most potent predictor of total cardiac death, the prediction of sudden death in patients without symptoms with DCM is poor. Studies with either class I antiarrhythmic drugs or amiodarone have not yet demonstrated a reduction in total mortality rates or sudden death. The usefulness of an implantable cardioverter defibrillator (ICD) in patients without symptoms with DCM is currently under investigation. The usefulness of serial electropharmacologic testing for patients with documented sustained ventricular tachycardia or ventricular fibrillation and DCM is still controversial. Because most patients with DCM and VT or out-of-hospital cardiac arrest have either no inducible ventricular tachyarrhythmia at baseline or the reproducibility of ventricular tachycardia/ventricular fibrillation induction is poor, implantation of an ICD should be considered in most of these patients. The indication for implantation of an ICD should be made on clinical judgment of the patient's functional status and other prognosis-limiting factors, such as rapid progression of heart failure, end-stage heart failure, and age.

Antiarrhythmic therapy in patients with congestive heart failure

Current information suggests that in patients with congestive heart failure (CHF) who have asymptomatic ventricular arrhythmias, coronary artery disease (dilated ischemic cardiomyopathy), and a positive signal-averaged electrocardiogram, electrophysiologic studies are useful for stratifying risk and guiding therapy. Therapy with amiodarone hydrochloride (Cordarone) appears to improve survival in patients after myocardial infarction. In CHF patients with asymptomatic ventricular arrhythmias and dilated nonischemic cardiomyopathy, electrophysiologic studies are of little value in risk stratification because of their low yield of sustained monomorphic tachycardias. There is little evidence that therapy with conventional antiarrhythmic agents improves survival. Although amiodarone can suppress ventricular ectopic beats, no trial yet conducted has detected an effect on mortality. Randomized, controlled trials with low-dose amiodarone are needed for more definitive information. Most symptomatic patients should undergo electrophysiologic testing and receive guided therapy, either with antiarrhythmic drugs or with an implantable cardioverter-defibrillator.

The clinical significance of nonsustained ventricular tachycardia

Nonsustained ventricular tachycardia (NSVT) is an arrhythmia not often associated with symptoms; however, its occurrence in patients with structural heart disease is a prognostic indicator of an increased risk of mortality and sudden death. The management of asymptomatic patients with NSVT should first attempt to identify which patients are at highest risk for cardiac arrest, and second, devise a treatment that can reduce the incidence and/or mortality of cardiac arrest in this group. In patients with chronic coronary artery disease (CAD) and NSVT, programmed electrical stimulation identifies both a low and high risk group with respect to occurrence of ventricular arrhythmias. The negative predictive value of programmed electrical stimulation in patients with CAD and NSVT has been well established; however, uncertainty remains as to the optimal therapy for CAD patients with inducible ventricular arrhythmias. A number of reports suggest that patients whose inducible ventricular arrhythmias are rendered noninducible with antiarrhythmic drugs have a much lower risk of sudden death. It is yet to be resolved whether arrhythmias rendered noninducible identify a subgroup at low risk for cardiac arrest, independent of treatment. There is some evidence to suggest that the frequency of NSVT in patients with nonischemic dilated cardiomyopathy identifies a group at higher risk of sudden death. Programmed electrical stimulation adds little in helping to identify which of these patients are most likely to have cardiac arrest. The presence of NSVT in asymptomatic patients with hypertrophic cardiomyopathy may identify a group at higher risk for cardiac arrest.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonsustained ventricular tachycardia: identification and management of high-risk patients

NSVT is common in normal persons and in patients with a variety of heart diseases. When present in patients with coronary artery disease, particularly after a recent myocardial infarction, it is associated with an increased risk of sudden and nonsudden cardiac death. However, its prognostic significance in patients with nonischemic heart disease, with the possible exception of hypertrophic cardiomyopathy, remains controversial. In patients with coronary artery disease, certain diagnostic tools (e.g., determination of left ventricular function. PVS) help to identify low- and high-risk patients who may or may not benefit from antiarrhythmic treatment. There is no consensus at this point as to the best approach for identifying and treating high-risk patients. Ongoing clinical trials should provide important information on the roles of signal-averaged ECGs and PVS in the management of patients with NSVT and coronary artery disease. In the meantime, treatment should be individualized for each patient. beta-Blockers should probably be the first line of therapy to control symptoms. Asymptomatic potentially high-risk patients (i.e., those with LVEF < 40%) should be referred for enrollment in randomized controlled studies.

Sudden death in idiopathic dilated cardiomyopathy: role of ventricular arrhythmias

Sudden cardiac death (SCD) is associated with idiopathic congestive cardiomyopathy (IDCM) and most commonly is due to ventricular tachyarrhythmias. The recurrence rate of SCD in the absence of specific therapy is thought to be around 20%-30% per year. Asymptomatic and symptomatic ventricular arrhythmias are common in patients with IDCM and the direct causal link of such arrhythmias with SCD in IDCM patients remains to be established. Furthermore, therapy directed at suppressing these ventricular arrhythmias has not been shown to decrease the incidence of SCD. Various approaches such as ambulatory monitoring, electrophysiological testing, signal-averaged electrocardiogram, and hemodynamics have met with variable success in identifying patients prone to SCD. Additionally, therapeutic approaches to prevent SCD in IDCM patients have produced equivocal results. This article reviews the published studies addressing the causal link of ventricular arrhythmias to sudden death in patients with IDCM and the attempts to decrease the incidence of sudden.

Prognostic value of an abnormal signal-averaged electrocardiogram in patients with nonischemic congestive cardiomyopathy

BACKGROUND

An abnormal signal-averaged ECG (SAECG) has predictive value for arrhythmic events in patients with coronary artery disease. The purpose of this study was to investigate whether an abnormal SAECG could provide prognostic information in patients with nonischemic dilated cardiomyopathy.

METHODS AND RESULTS

We prospectively obtained SAECGs in 114 patients with dilated nonischemic cardiomyopathy. Twelve-lead ECGs, left ventricular ejection fractions, hemodynamic measurements, and peak exercise oxygen consumption (VO2) also were measured. An SAECG was defined as abnormal by any one of the three following criteria: filtered QRS duration > 120 msec, root-mean-square voltage in the last 40 msec < 20 microV, or duration < 40 microV > 38 msec at 40 Hz. Sixty-six patients had a normal SAECG, 20 patients had an abnormal SAECG, and 28 patients had bundle branch block (BBB). Mean follow-up was 10 +/- 5 months. Age, ejection fraction, peak VO2, pulmonary capillary wedge pressure, and cardiac index were not statistically different among the three groups. Use of antiarrhythmic drugs was similar among the three groups, although patients with BBB had more implantable defibrillators (p < 0.05). The incidence of previous atrial arrhythmias was similar for the three groups. Patients with abnormal SAECG or BBB had more past episodes of sustained ventricular tachycardia and/or sudden death episodes (n = 9) than patients with normal SAECG (n = 1) (p < 0.01). Prospectively, none of the 66 patients with normal SAECG died suddenly or had sustained ventricular arrhythmias. Two deaths occurred from progressive heart failure, and three patients required urgent transplant. In the 20 patients with an abnormal SAECG, four patients had sustained ventricular tachycardia, five patients died suddenly, two patients died from progressive heart failure, and one patient required urgent transplant. In the patients with BBB, four patients had sustained ventricular tachycardia, and four patients required urgent transplant. One-year event-free survival, i.e., absence of ventricular tachycardia and/or death, was 95% in patients with normal SAECG, 88% in patients with BBB, and only 39% in patients with an abnormal SAECG (p < 0.001). Multivariate analysis demonstrated that SAECG and New York Heart Association classification were independent predictors of survival.

CONCLUSIONS

Patients with an abnormal SAECG had a statistically significant increase in sustained ventricular arrhythmias and/or death than did patients with a normal SAECG or BBB. This study demonstrates that an abnormal SAECG is a marker of past and future arrhythmic events in patients with nonischemic dilated cardiomyopathy. In contrast, patients with a dilated cardiomyopathy with a normal SAECG have an excellent prognosis with adverse outcome only from progressive heart failure.

Syncope in advanced heart failure: high risk of sudden death regardless of origin of syncope

OBJECTIVES

The purpose of this study was to assess the importance of syncope as a warning sign for sudden death in advanced heart failure and to determine the relative importance of cardiac syncope and syncope from other causes.

BACKGROUND

Despite remarkable advances in the pharmacologic approach to advanced heart failure, 20% to 40% of patients with advanced heart failure will die each year. In such patients, the relation between sudden death and the etiology of syncope has not been evaluated.

METHODS

The relation of syncope to sudden death was evaluated in 491 consecutive patients with advanced heart failure (New York Heart Association functional class III or IV), no history of cardiac arrest and a mean left ventricular ejection fraction of 0.20 +/- 0.07. Patients were evaluated for the presence and origin of syncope. The severity of heart failure was assessed from serum sodium levels, ejection fraction, functional class and echocardiographic and hemodynamic variables.

RESULTS

Sixty patients (12%) had a history of syncope; the condition had a cardiac origin in 29 (48%) and was due to other causes in 31 (52%). The origin of heart failure was coronary artery disease in 234 patients (48%) and dilated cardiomyopathy in 253 (51%) and its severity was similar in patients with and without syncope. During a mean follow-up interval of 365 +/- 419 days, 69 patients (14%) died suddenly and 66 patients (13%) died of progressive heart failure. The actuarial incidence of sudden death by 1 year was significantly greater in patients with (45%) than in those without (12%, p < 0.00001) syncope. In the Cox proportional hazards model, syncope predicted sudden death independent of atrial fibrillation, serum sodium, cardiac index, angiotensin-converting enzyme inhibition and patient age. The actuarial risk of sudden death by 1 year was similarly high in patients with either cardiac syncope or syncope from other causes (49% vs. 39%, p = NS).

CONCLUSIONS

Patients with advanced heart failure are at especially high risk for sudden death regardless of the etiology of syncope.