Prognostic significance of programmed ventricular stimulation in patients surviving complicated acute myocardial infarction: a prospective study.

In survivors of complicated myocardial infarction, the inducibility of sustained ventricular tachycardia may help identify a subset that is at increased risk for subsequent sudden cardiac death or spontaneous sustained ventricular tachycardia. We performed prehospital discharge programmed ventricular stimulation in 86 survivors of acute myocardial infarction complicated by heart failure, angina pectoris, or nonsustained ventricular tachycardia. These patients also underwent cardiac catheterization with coronary angiography and 24-hour ambulatory ECG recording. Programmed ventricular stimulation induced sustained ventricular tachycardia in 19 patients (22%) and ventricular fibrillation in six (7%) and did not induce these arrhythmias in 61 patients (71%). During an average follow-up of 18 +/- 13 months, 11 patients had arrhythmic events (seven sudden death and four nonfatal spontaneous sustained ventricular tachycardia) and 10 patients had nonsudden cardiac death. The total cardiac mortality rate was 20%. Arrhythmic events occurred in 32% of the 19 patients with inducible sustained ventricular tachycardia compared with 7% of the remaining 67 patients (p less than 0.003). By multivariate analysis the occurrence of arrhythmic events was independently predicted by both inducible sustained ventricular tachycardia and Killip class III or IV heart failure. The risk of arrhythmic events was 4.4% in the absence of both variables versus 38.4% (p less than 0.001) when both variables were present. The total cardiac mortality rate was best predicted by low left ventricular ejection fraction (less than 30%). Thus programmed ventricular stimulation is useful in risk stratification of survivors of complicated acute myocardial infarction. The prognostic utility appears to be particularly high in patients with infarction complicated by Killip class III or IV heart failure.     

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 ≤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 ≤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.     

Low recurrence of syncope in patients with inducible sustained ventricular tachyarrhythmias treated with an implantable cardioverter-defibrillator.

AIMS: To determine the effectiveness of the implantable cardioverter defibrillator (ICD) in preventing recurrence of syncope in patients with structural heart disease, previously unexplained syncope and inducible ventricular arrhythmias. METHODS: Thirty-eight patients with syncope, structural heart disease and inducible arrhythmias had an ICD implanted. All ICDs delivered antitachycardia pacing and shocks of adjusted energy. Detection and therapy were programmed according to uniform criteria. RESULTS: The mean age of the patients was 63+/-11 years and most of them were male (36/38). After a mean follow-up of 28+/-15 (4-61) months, six patients died and one underwent heart transplantation. Syncope recurred in three patients, but in none of them was it caused by an arrhythmic event. In 18 patients, 113 episodes of ventricular tachycardia/ventricular fibrillation were detected and appropriately treated by the ICD. The mean time from implant until first appropriate therapy was 18+/-14 months. The actuarial probability of receiving appropriate therapy was 20% and 42% at 12 and 24 months, respectively. CONCLUSIONS: In patients with unexplained syncope, structural heart disease and inducible arrhythmias, ICD prevents syncope associated with arrhythmic events. Frequent effective use of antitachycardia pacing and shocks of adjusted energy seem essential to this aim.     

Electrophysiological testing and nonsustained ventricular tachycardia. Use and limitations in patients with coronary artery disease and impaired ventricular function

Electrophysiological testing was performed in 100 consecutive patients with spontaneous asymptomatic nonsustained ventricular tachycardia, chronic coronary artery disease, and ejection fraction of less than 40%. Fifty-seven patients without inducible sustained ventricular arrhythmias were discharged on no antiarrhythmic therapy. Sustained monomorphic ventricular tachycardia was induced in 37 patients, and polymorphic ventricular tachycardia or ventricular fibrillation was induced in six patients. Of the 43 patients with inducible sustained ventricular arrhythmias, three had spontaneous cardiac arrest during serial drug testing and were excluded from further analysis. Twenty patients were discharged on drug therapy, resulting in suppression of inducible sustained ventricular arrhythmias. The remaining 20 patients with persistently inducible sustained arrhythmias were discharged on drug therapy, resulting in maximal rate slowing of the induced tachycardia. During a mean follow-up of 16.7 months, there were 10 recurrent cardiac arrests or sudden deaths. The 1- and 2-year actuarial incidence of these events was 2% and 6%, respectively, in patients without inducible sustained ventricular arrhythmias; 0% and 11%, respectively, in patients in whom inducible arrhythmias were suppressed; and 34% and 50%, respectively, in patients with persistently inducible sustained ventricular arrhythmias. Multivariate Cox analysis identified only the persistence of inducible sustained ventricular arrhythmias as a significant independent predictor of sudden death or recurrent sustained arrhythmias (p less than 0.001; relative risk, 3.5; 95% confidence intervals, 2.1-4.9). In this population, therapeutic intervention to prevent sudden death is unnecessary in patients without inducible sustained ventricular arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of the Automatic Implantable Cardioverter Defibrillator in the Post-myocardial Infarction Patient

Patients with a myocardial infarction are at an increased risk of sudden cardiac death largely due to ventricular arrhythmias associated with myocardial scarring. Implantable cardioverter defibrillators (ICDs) have been established as the best available treatment for the secondary prevention of an arrhythmic death in patients at high risk. This includes patients who have survived sudden cardiac death, have had sustained ventricular tachycardia or fibrillation, or have had syncope assumed to be due to a ventricular arrhythmia. High-risk features of patients with infarction without a previous arrhythmic event who qualify for a primary prevention ICD are an ejection fraction (EF) <30% or symptoms of Class II or III heart failure with an EF ≤ 35%. In addition, patients with nonsustained ventricular tachycardia, a positive electrophysiology study, and EF ≤ 40% are candidates under the current primary prevention guidelines. The current guidelines have specified the timing for ICD implantation as >40 days following the acute myocardial infarction. Despite the establishment of the guidelines, current clinical practice has revealed that ICDs are underutilized in patients who qualify. This article reviews the ICD implantation guidelines to encourage the appropriate use of the device.     

Risk stratification and long-term therapy with amiodarone in patients with idiopathic dilated cardiomyopathy]

Patients with cardiomyopathy are known to suffer from a high prevalence of tachyarrhythmic complications and sudden cardiac death. In a prospective study, 30 patients (25 men, 5 women, mean age: 52 +/- 12 years) with dilated cardiomyopathy underwent 48-h-Holter monitoring and programmed electrical stimulation and, independent from the results of the diagnostic work-up, were then randomized either to amiodarone or to a conventional or no antiarrhythmic therapy. At baseline, frequent ventricular arrhythmias (> 30 ventricular premature beats/h) were observed in 15/30 patients (50%), 13 patients (43%) had repetitive ventricular arrhythmias, additionally. Four patients suffered spontaneous sustained tachyarrhythmias. During programmed electrical stimulation, sustained monomorphic ventricular tachycardia was induced in 3/3 patients with and in 1/25 patients (4%) without a history of sustained tachycardia. Sustained monomorphic ventricular tachycardia was induced with one to two extrastimuli; three extrastimuli only increased the incidence of inducible ventricular fibrillation (8 patients, 28%). During a mean follow-up of 28 +/- 6 months 10/30 patients (33%) died for cardiac reasons (sudden cardiac death: 4/10 patients). Cardiac death was most likely in patients with a left-ventricular ejection fraction < 35% (5/18 patients, 28% versus 1/12 patients with ejection fraction > 35%, 8%) and further increased in the presence of reduced exercise tolerance and frequent and repetitive ventricular arrhythmias (4/7 patients, 57%). In the amiodarone group 4/15 patients died (27%, sudden cardiac death: one patient), while in patients not treated by amiodarone 8/15 patients died (54%; sudden cardiac death: three patients). Amiodarone therapy was well tolerated in all but one patient.     

Devices for the management of ventricular arrhythmias in cardiac failure

Heart failure is a common clinical syndrome with a high morbidity and mortality. Despite advances in medical treatment, death from dangerous ventricular arrhythmias is frequently implicated. Emerging evidence supports the use of the implantable cardioverter defibrillator for selected patients. This includes secondary prevention indications for patients who have survived life-threatening ventricular arrhythmias. In addition, patients who have not suffered spontaneous sustained ventricular arrhythmias, but who are at high risk for sudden arrhythmic death are starting to be recognized as candidates for ICD therapy. At present the only primary prevention indication with a good evidence base is the presence of inducible ventricular arrhythmias at electrophysiologic testing in patients with prior myocardial infarction, impaired left ventricular systolic function and non-sustained ventricular tachycardia on Holter monitoring. Studies planned or in progress are likely to expand further the role of device therapy in the treatment of patients with cardiac failure.     

Long-term arrhythmic outcome in survivors of ventricular fibrillation with absence of inducible ventricular tachycardia

While programmed electrical stimulation of the heart is useful in directing therapy in cardiac arrest survivors who exhibit inducible ventricular tachycardia (VT), controversy exists as to the risk of recurrent ventricular fibrillation (VF) and need for antiarrhythmic therapy in patients without inducible VT during drug-free control programmed stimulation studies. In this study, the clinical features and arrhythmic outcome of 43 survivors of VF without inducible VT at control programmed stimulation were examined. In 38 patients, factors that may have played a potentiating role in the genesis of VF included ischemia in 15, proarrhythmia in 18, rapid rate response to atrial fibrillation in 3 and acute alcoholism in 2. Three patients required antiarrhythmic drugs for supraventricular tachyarrhythmia and 40 patients were discharged without antiarrhythmic therapy. At 32 +/- 21 months (range 1 to 82), 37 (92%) have remained free of arrhythmic recurrence while 3 have had sustained subsequent major arrhythmic events (syncope 1 patient, VF 1, sudden cardiac death 1). Thus, survivors of VF without inducible VT at drug-free control programmed stimulation are characterized by (1) potentiating factors--often identifiable and correctable--that may be important to the genesis of VF; (2) generally low risk of arrhythmic recurrence; and (3) effective long-term management often achieved without the use of additional antiarrhythmic drugs or antitachycardia/defibrillation devices.     

Programmed stimulation in patients with malignant ventricular arrhythmias. I: Diagnostic value

Sudden cardiac death is a leading cause of death in industrially developed countries and accounts for approximately 90 000 deaths yearly in the FRG. While the majority of victims have severe coronary heart disease, sudden cardiac death is infrequently caused by acute myocardial infarction (20%) but is predominantly related to malignant ventricular arrhythmias (i.e., ventricular fibrillation or sustained ventricular tachycardia). Patients with a history of such malignant ventricular arrhythmias are at high risk for sudden death. Spontaneous occurrence of sustained ventricular tachycardia and of ventricular fibrillation is critically related to two factors: 1. trigger-arrhythmias consisting usually of complex ventricular extrasystoles (Lown classification IV to V); 2. increased vulnerability of the myocardium representing the target organ for trigger-arrhythmias. While trigger-arrhythmias can be easily recorded by noninvasive techniques including Holter monitoring or exercise and stress ECG, ventricular vulnerability is more difficult to determine and often requires ventricular stimulation with intracardiac electrocatheters. In patients with documented spontaneous malignant ventricular arrhythmias, two aspects of programmed stimulation must be considered: 1. diagnostic, and more importantly, 2. therapeutic purposes of this method. Diagnostic purposes include determination of the mode of initiation and unequivocal ventricular localization of the tachycardia excluding other arrhythmias with broad QRS complex. In patients with spontaneous sustained ventricular tachycardia, programmed stimulation can reproducibly initiate the clinical arrhythmia in 85% (sensitivity and specificity of the method approximately 90%). In patients with cardiac arrest due to ventricular fibrillation, programmed stimulation is less reliable (50%). However, the main purpose of programmed stimulation in patients with documented clinical malignant arrhythmias is not diagnostic or prognostic evaluation but is serial electrophysiological studies for individual optimization of antiarrhythmic therapy.     

Sudden cardiac death in Chagas' heart disease in the contemporary era

This article reviews epidemiology, clinical-morphological aspects, and primary and secondary prevention of sudden cardiac death in patients with chronic Chagas' heart disease in the current era. Chagas' disease patients with life-threatening ventricular tachyarrhythmias are at risk of sudden cardiac death. No evidence-based support is available for guiding prophylaxis of sudden cardiac death in patients with this condition. Therefore, measurements for sudden cardiac death prevention in Chagas' disease patients have been derived from data obtained in non-Chagas' disease patients as well as on expertise of physicians dealing with this disorder in areas where Chagas' disease is endemic. For primary prevention, therefore, we suggest that patients with non-sustained VT be referred to programmed ventricular stimulation. Patients with inducible VT will be better treated with Implantable Cardioverter-Defibrillator (ICD) than with amiodarone therapy. For secondary prevention, we suggest that patients with malignant ventricular tachyarrhythmias with hemodynamic instability receive ICD therapy. For patients with life-threatening ventricular arrhythmias and no hemodynamic instability, however, secondary prevention can be accomplished with ICD therapy or catheter ablation in those with a left ventricular ejection fraction (LVEF) of 30% or less, and with electrophysiologic testing-guided drug therapy or empiric treatment with amiodarone in those with a LVEF of 30% or high.     

A comparison of T-wave alternans, signal averaged electrocardiography and programmed ventricular stimulation for arrhythmia risk stratification

OBJECTIVES

The goal of this study was to compare T-wave alternans (TWA), signal-averaged electrocardiography (SAECG) and programmed ventricular stimulation (EPS) for arrhythmia risk stratification in patients undergoing electrophysiology study.

BACKGROUND

Accurate identification of patients at increased risk for sustained ventricular arrhythmias is critical to prevent sudden cardiac death. T-wave alternans is a heart rate dependent measure of repolarization that correlates with arrhythmia vulnerability in animal and human studies. Signal-averaged electrocardiography and EPS are more established tests used for risk stratification.

METHODS

This was a prospective, multicenter trial of 313 patients in sinus rhythm who were undergoing electrophysiologic study. T-wave alternans, assessed with bicycle ergometry, and SAECG were measured before EPS. The primary end point was sudden cardiac death, sustained ventricular tachycardia, ventricular fibrillation or appropriate implantable defibrillator (ICD) therapy, and the secondary end point was any of these arrhythmias or all-cause mortality.

RESULTS

Kaplan-Meier survival analysis of the primary end point showed that TWA predicted events with a relative risk of 10.9, EPS had a relative risk of 7.1 and SAECG had a relative risk of 4.5. The relative risks for the secondary end point were 13.9, 4.7 and 3.3, respectively (p < 0.05). Multivariate analysis of 11 clinical parameters identified only TWA and EPS as independent predictors of events. In the prespecified subgroup with known or suspected ventricular arrhythmias, TWA predicted primary end points with a relative risk of 6.1 and secondary end points with a relative risk of 8.0.

CONCLUSIONS

T-wave alternans is a strong independent predictor of spontaneous ventricular arrhythmias or death. It performed as well as programmed stimulation and better than SAECG in risk stratifying patients for life-threatening arrhythmias.     

Adjunctive therapy for recurrent ventricular tachycardia in patients with implantable cardioverter defibrillators

Implantable cardioverter defibrillators (ICDs) are now the mainstay of therapy in patients with sustained ventricular tachycardia (VT), ventricular fibrillation, resuscitated sudden cardiac death, or certain high-risk markers for these arrhythmic events. Although ICDs in such patients can be life-saving, they can impair quality of life when painful or frequent discharges occur or when residual VT symptoms recur prior to delivery of ICD therapies. As such, antiarrhythmic drugs often are employed in an attempt to reduce the triggering tachyarrhythmic events. Recently, studies with beta-blockers, sotalol, amiodarone, and the investigational agent azimilide have been performed to objectify the efficacy, benefits, or risks of such therapies when administered to patients with ICDs. This review describes the considerations important to the use of these therapies in ICD patients and the results and applicability of these investigative studies.     

Programmed ventricular stimulation after myocardial infarction does not help reduce the risk of ventricular events

Summary Programmed ventricular stimulation could be a useful technique to detect patients at high risk for ventricular arrhythmias and sudden death after acute myocardial infarction. However, prevention of arrhythmic events using this technique has never been demonstrated. To determine whether prophylactic antiarrhythmic therapy influences prognosis after acute myocardial infarction, 196 patients without spontaneous ventricular tachycardia (VT) but with inducible sustained monomorphic VT were followed for 3±1 years. Ninety-seven patients were not treated (control group). In 99 patients (study group), the antiarrhythmic therapy was guided by electrophysiologic study: One to four trials using class I, II, and III antiarrhythmic drugs were performed until the VT was not inducible or the induced VT was slower and was associated with hemodynamic stability. An effective antiarrhythmic drug prevented VT induction in 34 patients (34%; group I). Sixty-five patients (group II) still had inducible VT with the antiarrhythmic drug. Group II differed from group I in having a higher incidence of an inferior myocardial infarction location (57% vs. 47%; NS), a lower left ventricular ejection fraction (36.5% vs. 41%; NS), a slower rate of induced VT in the control state (227 vs. 255 beats/min; p<0.05), and a higher number of drug trials (1.9 vs. 1.3; p<0.001). During the follow-up in the control group and in groups I and II, the incidence of total cardiac events was 25%, 15%, and 16% (NS), respectively, and the incidence of total arrhythmic events (VT, sudden death) was 18.5%, 9%, and 12% (NS). Only the risk of VT was reduced (14%, 0%, and 4%; p<0.05). In conclusion, guided-antiarrhythmic therapy, including class III agents after acute myocardial infarction, was successful in only 34% of patients, and the incidence of arrhythmic events was not significantly decreased. Therefore, programmed ventricular stimulation does not help in managing patients at risk of ventricular arrhythmia after myocardial infarction but could help to indicate the need for nonmedical treatment, such as device therapy.     

Prognostic significance of programmed ventricular stimulation in survivors of acute myocardial infarction

The prognostic significance of the response to programmed ventricular stimulation was studied in 75 stable survivors of acute myocardial infarction. Programmed ventricular stimulation induced sustained ventricular arrhythmias in 33 (44%) patients and did not induce these arrhythmias in 42 (56%) patients. During a mean follow up of 18 months, four patients died suddenly and three developed spontaneous sustained ventricular tachycardia. The occurrence of arrhythmic events was not significantly different in patients with inducible sustained arrhythmias and those without, but such events were predicted by the presence of mild congestive heart failure. Although the inducibility of sustained ventricular tachycardia (but not ventricular fibrillation) seemed to identify a high risk subset with an arrhythmic event rate of 21% compared with 5.5% in others, it had a low sensitivity (57%) and a low positive predictive accuracy (21%) for arrhythmic events. Programmed ventricular stimulation is not helpful in identifying a subset of patients at high risk after an uncomplicated acute myocardial infarction.     

Prognostic significance of programmed ventricular stimulation in survivors of acute myocardial infarction.

The prognostic significance of the response to programmed ventricular stimulation was studied in 75 stable survivors of acute myocardial infarction. Programmed ventricular stimulation induced sustained ventricular arrhythmias in 33 (44%) patients and did not induce these arrhythmias in 42 (56%) patients. During a mean follow up of 18 months, four patients died suddenly and three developed spontaneous sustained ventricular tachycardia. The occurrence of arrhythmic events was not significantly different in patients with inducible sustained arrhythmias and those without, but such events were predicted by the presence of mild congestive heart failure. Although the inducibility of sustained ventricular tachycardia (but not ventricular fibrillation) seemed to identify a high risk subset with an arrhythmic event rate of 21% compared with 5.5% in others, it had a low sensitivity (57%) and a low positive predictive accuracy (21%) for arrhythmic events. Programmed ventricular stimulation is not helpful in identifying a subset of patients at high risk after an uncomplicated acute myocardial infarction.     

Prognostic significance of ventricular late potentials in the postmyocardial infarction period

Ventricular late potentials in patients after myocardial infarction can be assumed to herald an increased risk of future sudden cardiac death or symptomatic sustained ventricular tachycardia. This holds particularly true for patients studied early after recent myocardial infarction whereas patients assessed later in the subsequent course have a substantially lesser incidence of arrhythmic events, probably due to intercurrent death of those at high risk. Of prognostic importance appears not only the presence but also the duration of late potentials. A meaningful role is also assumed by the extent of left ventricular functional impairment (EF less than 40%). However, in consideration of the complex mechanisms that can lead to sudden cardiac death, no single method predicts with high sensitivity the occurrence of a ventricular tachyarrhythmic event. Sudden cardiac death can be incurred on the basis of chronic electrophysiological abnormalities as a consequence of regional slow conduction in the border zone of a previous myocardial infarction precipitated by trigger factors such as spontaneous ventricular arrhythmias. Sudden cardiac death or symptomatic sustained ventricular tachycardia can also occur due to sudden and transient changes in the electrophysiological properties of the myocardium due to ischemia. Whether the combination of late potentials with clinical parameters such as ventricular arrhythmias detected in the ambulatory ECG and those induced with programmed electrical stimulation will lead to more accurate identification of patients at risk prerequisites further elucidation. Currently available literature indicates that in patients with late potentials, ventricular tachycardias can be induced more frequently by programmed electrical stimulation and that the combination of both phenomena confers a particularly high risk.     

Implantable defibrillator event rates in patients with unexplained syncope and inducible sustained ventricular tachyarrhythmias: a comparison with patients known to have sustained ventricular tachycardia

OBJECTIVES

To assess the clinical significance of inducible ventricular tachyarrhythmias among patients with unexplained syncope.

BACKGROUND

Induction of sustained ventricular arrhythmias at electrophysiology study in patients with unexplained syncope and structural heart disease is usually assigned diagnostic significance. However, the true frequency of subsequent spontaneous ventricular tachyarrhythmias in the absence of antiarrhythmic medications is unknown.

METHODS

In a retrospective case-control study, the incidence of implantable cardiac defibrillator (ICD) therapies for sustained ventricular arrhythmias among patients with unexplained syncope or near syncope (syncope group, n = 22) was compared with that of a control group of patients (n = 32) with clinically documented sustained ventricular tachycardia (VT). Sustained ventricular arrhythmias were inducible in both groups and neither group received antiarrhythmic medications. All ICDs had stored electrograms or RR intervals. Clinical variables were similar between groups except that congestive cardiac failure was more common in the syncope group.

RESULTS

Kaplan-Meier analysis of the time to first appropriate ICD therapy for syncope and control groups produced overlapping curves (p = 0.9), with 57 ± 11% and 50 ± 9%, respectively, receiving ICD therapy by one year. In both groups, the induced arrhythmia was significantly faster than spontaneous arrhythmias, but the cycle lengths of induced and spontaneous arrhythmias were positively correlated (R = 0.6, p < 0.0001). During follow-up, three cardiac transplantations and seven deaths occurred in the syncope group, and two transplantations and five deaths occurred in the control group (36-month survival without transplant 52 ± 11% and 83 ± 7%, respectively, p = 0.03).

CONCLUSIONS

In patients with unexplained syncope, structural heart disease and inducible sustained ventricular arrhythmias, spontaneous sustained ventricular arrhythmias occur commonly and at a similar rate to patients with documented sustained VT. Thus, electrophysiologic testing in unexplained syncope can identify those at risk of potentially life-threatening tachyarrhythmias, and aggressive treatment of these patients is warranted.     

Ventricular Arrhythmias in the North American Multidisciplinary Study of ARVC : Predictors,Characteristics, and Treatment

Background

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is associated with sudden cardiac death. However, the selection of patients for implanted cardioverter-defibrillators (ICDs), as well as programming of the ICD, is unclear.

Objectives

The objective of this study was to identify predictors, characteristics, and treatment of ventricular arrhythmias in patients with ARVC.

Methods

The Multidisciplinary Study of Right Ventricular Cardiomyopathy established the North American ARVC Registry and enrolled patients with a diagnosis of ARVC. Patients were followed prospectively.

Results

Of 137 patients enrolled, 108 received ICDs. Forty-eight patients had 502 sustained episodes of ventricular arrhythmias, including 489 that were monomorphic and 13 that were polymorphic. In the patients with ICDs, independent predictors of ventricular arrhythmias in follow-up included spontaneous sustained ventricular arrhythmias before ICD implantation and T-wave inversions inferiorly. The only independent predictor for life-threatening arrhythmias, defined as sustained ventricular tachycardia (VT) ≥240 beats/min or ventricular fibrillation, was a younger age at enrollment. Anti-tachycardia pacing (ATP), independent of the cycle length of the VT, was successful in terminating 92% of VT episodes.

Conclusions

In the North American ARVC Registry, the majority of ventricular arrhythmias in follow-up are monomorphic. Risk factors for ventricular arrhythmias were spontaneous ventricular arrhythmias before enrollment and a younger age at ICD implantation. ATP is highly successful in terminating VT, and all ICDs should be programmed for ATP, even for rapid VT.     

Long-term follow-up of sudden cardiac arrest survivors and electrophysiologically guided antiarrhythmic therapy

Sudden cardiac arrest survivors have a high risk of suffering from recurrent arrhythmic events. Recent studies have shown that these patients have a significantly decreased mortality rate, if they are supplied with an implantable cardioverter/defibrillator (ICD). The aim of this study was to evaluate the long-term prognosis of patients with electrophysiologically guided antiarrhythmic drug therapy in comparison to patients with ICD. 204 consecutive survivors of sudden cardiac arrest were enrolled in this study. All patients were examined with an initial electrophysiologic study (EPS) with programmed ventricular stimulation. Patients were treated with antiarrhythmic drugs (if the inducible tachycardia was suppressed) or with the implantation of an ICD. The maximal follow-up period was 120 months, the mean period was 53.3 +/- 31.4 months (ICD) versus 60.3 +/- 35.5 months (EPS, nonsignificant). Patients with ICD showed an overall mortality rate of 14.6%, whereas EPS-guided patients had a mortality rate of 43.2% (p < 0.001). The cardiac and arrhythmogenic mortality rates were significantly lower in the ICD group (12 vs. 43%, p < 0.01, and 1 vs. 16%, p < 0.001, respectively). A reduction of the mortality risk was observed in the ICD group by up to 61% (all-cause mortality), 52% (cardiac mortality) and 97.2% (arrhythmogenic mortality). In arrhythmic event survivors with ICD, arrhythmic and overall mortality rates are significantly lower compared to patients with an EPS-guided drug therapy. In the secondary prevention of sudden cardiac death, ICD should be the first choice of antiarrhythmic therapy.     

Repolarization variability in the risk stratification of MADIT II patients.

AIMS: QT variability has been reported to be associated with ventricular arrhythmias and sudden cardiac death. There is limited data regarding variability in T-wave morphology and its prognostic value. In this study, we present a novel approach for the measurement of T-wave variability (TWV) reflecting changes in T-wave morphology, and we investigate the prognostic significance of Holter-derived TWV in patients with and without ventricular arrhythmias requiring appropriate implantable cardioverter defibrillator (ICD) therapy from the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II). Methods Study population consisted of 275 ICD patients from MADIT II after excluding patients with intraventricular conduction abnormalities or atrial fibrillation. TWV was measured based on amplitude variance of T-wave amplitude. Results During 2-year follow-up, 58 (21%) patients had appropriate ICD therapy for ventricular tachycardia or fibrillation. Patients with appropriate ICD therapy had higher levels of TWV measures than those without arrhythmic events. After adjustment for heart rate, ejection fraction, and significant clinical predictors of arrhythmic events, a Cox proportional-hazards regression model revealed that dichotomized TWV values were predictive for ventricular tachyarrhythmias requiring appropriate ICD therapy (hazard ratio, 2.0; 95% CI; 1.2-3.5; P=0.01). On the basis of the comprehensive testing, TWV value >59 microV was found predictive for arrhythmic events in MADIT II population. CONCLUSION: Our newly designed method for the assessment of repolarization variability in ambulatory Holter recordings detected transient variability of T-wave morphology, which was predictive for ventricular tachyarrhythmias in the MADIT II population.