Programmed ventricular stimulation in survivors of acute myocardial infarction: long-term follow-up

What is The Utility of Electrophysiological Study in Elderly Patients with Syncope and Heart Disease?

BACKGROUND

Syncope in elderly patients with heart disease is a growing problem. Its aetiological diagnosis is often difficult. We intended to investigate the value of the electrophysiological study (EPS) in old patients with syncope and heart disease.

METHODS

EPS was performed in 182 consecutive patients with syncope and heart disease, among whom 62 patients were ≥75 years old and 120 patients <75.

RESULTS

Left ventricular ejection fraction was 43.9±11.7% in patients ≥75 and 41.1±12.6% in patients <75. During EPS, induced sustained ventricular arrhythmias were as frequent in both groups (27.4% in patients ≥75 versus 27.5% in patients <75, p=0.99) whereas AV conduction abnormalities were more frequent in older patients (37.1% in patients ≥75 versus 18.3% in patients <75, p<0.005). Syncope remained unexplained in 35.5% of patients ≥75 and in 51.7% of patients <75 (p>0.04). ICD was more likely to be implanted in younger patients than in patients ≥75 years (37.5% vs 21% respectively, p<0.009). During a mean follow-up period of 3.3±3 years, the 4-year-survival rate was 66.9±6.8 % in patients ≥75 and 75.9±6.2 % in patients <75 years. The main cause of death was heart failure in both groups. The factors related to a worse outcome in a multivariate analysis were low LVEF and higher age.

CONCLUSION

Complete EPS allows the identification of treatable causes in a high proportion of elderly patients with syncope and heart disease. Yet, the prognosis of these patients is mainly related to LVEF and age.

Sudden cardiac death risk stratification in patients with heart failure

The multiplicity of mechanisms contributing to arrhythmogenesis in patients with heart failure carries obvious implications for risk stratification. If patients having the propensity to develop arrhythmias by these different mechanisms are to be identified, tests must be devised that reveal the substrates or other factors that relate to each mechanism. In the absence of this, efforts to risk stratify patients are likely to be neither cost-effective nor accurate. This article reviews the current knowledge base of risk stratification for sudden death in patients with heart failure, while acknowledging several limitations in the studies examined.

Significance of Inducible Ventricular Flutter-Fibrillation After Myocardial Infarction

AIM

The purpose of this study was to determine the factors associated with the induction of ventricular flutter/fibrillation (VFl/VF)and its prognostic significance in post-myocardial infarction.

METHODS

Programmed ventricular stimulation was performed after myocardial infarction (MI) for syncope (n = 232) or systematically (n = 755); 230 patients had an induced VFl/VF and were followed during 4 +/- 2 years.

RESULTS

VFl/VF was induced in 49/232 patients (21%) with syncope versus 181/755 asymptomatic patients (24%) (NS) and 94/410 patients (23%) with left ventricular ejection fraction (LVEF) <40% versus 136/577 patients (22.5%) with LVEF >40% (NS). Cardiac mortality was 9%; LVEF was 33 +/- 15% in patients who died, 43 +/- 13% in alive patients (P < 0.004). In patients with LVEF <40%, induced VFl/VF, mortality rate was 31% in those with syncope, 10% in asymptomatic patients (P < 0.001), because of an increase of deaths by heart failure; patients with LVEF >40% with or without syncope had a low mortality (5% and 3%). After linear logistic regression, VFl/VF and LVEF were predictors of total cardiac mortality, but only LVEF <40% predicted sudden death.

CONCLUSION

Syncope and the level of LVEF did not increase the incidence of VFl/VF induction after MI, but modified the cardiac mortality: induced VF increased total cardiac mortality in patients with syncope and LVEF <40%, but did not increase sudden death. In patients with LVEF >40%, induced VFl/VF has no significance neither in asymptomatic patients nor in those with syncope.

Differences in mechanisms and outcomes of syncope in patients with coronary disease or idiopathic left ventricular dysfunction as assessed by electrophysiologic testing

OBJECTIVES

This study evaluated the causes of syncope and the significance and differences in left ventricular (LV) dysfunction, coronary disease, and idiopathic dilated cardiomyopathy (DCM).

BACKGROUND

Risk stratification of and indications for an automated defibrillator could differ according to the cause of LV dysfunction.

METHODS

Electrophysiologic study, including atrial and ventricular programmed stimulation, was performed in 119 patients with coronary disease (group I) and 61 patients with DCM (group II) with an left ventricular ejection fraction (LVEF) <40% and syncope. Patients were followed from one to six years (mean 4 +/- 2 years).

RESULTS

Sustained monomorphic ventricular tachycardia (VT) was induced in 44 group I patients (37%) and 13 group II patients (21%); ventricular flutter (>270 beats/min) or ventricular fibrillation (VF) was induced in 24 group I patients (19%) and 9 group II patients (15%); and various other arrhythmias were identified. Syncope remained unexplained in 34 group I patients (30%) and 16 group II patients (27%). Prognosis depended on the heart disease: VT or VF induction was a predictive factor of mortality in coronary disease and identified a group with high cardiac mortality (46%), compared with patients with a negative study, who had a lower mortality (6%; p < 0.001) than in other studies. Cardiac mortality was only correlated with LVEF in DCM.

CONCLUSIONS

Various causes could explain syncope in 70% of patients with coronary disease and DCM, but differences were noted: VT was frequent in coronary disease with a bad prognosis, and ischemia could explain syncope; in DCM, different causes such as atrial tachycardia could be responsible for syncope, but the prognosis only depended on LVEF.

Long-term prognosis of inducible ventricular flutter: not an innocent finding

BACKGROUND

The prognostic significance of ventricular flutter (VFL) induced during programmed electrical stimulation (PES) is currently unknown.

METHODS

This study examined patients who had PES-induced VFL and assessed their long-term prognosis compared with patients who had inducible sustained monomorphic ventricular tachycardia (SMVT).

RESULTS

Of 3414 patients undergoing PES, 74 (2%) had sustained VFL. They were compared with a group of 71 patients undergoing PES in the same time frame who had inducible SMVT. Patients with inducible VFL had a higher ejection fraction than patients with SMVT (0.39 vs 0.33; P =.05). More aggressive pacing was required for arrhythmia induction in patients with VFL, with more stimuli (2.7 +/- 0.5 vs 2.2 +/- 0.6; P <.01) and tighter S(2), S(3), and S(4) intervals. After a mean follow-up of 30 +/- 31 months, the mortality rate was 34% in patients with VFL and 30% in patients with SMVT (P =.41). No difference in the 2 groups in overall survival or a combined end point of sudden death or appropriate implantable cardioverter defibrillator shock was revealed with Kaplan-Meier analysis.

CONCLUSION

The long-term prognosis of patients with inducible VFL is similar to that of patients with inducible SMVT, even when VFL is induced with a relatively aggressive protocol.

Significance of External Cardioversion Induced Atrial Tachyarrhythmias

External cardioversion is used to stop VT or VF in emergency. Supraventricular tachyarrhythmias are sometimes noted after cardioversion in patients known to be previously in sinus rhythm. The purpose of the study was to evaluate the significance of supraventricular tachyarrhythmias induced by external cardioversion. The study population consisted of 22 patients who developed supraventricular tachyarrhythmias after transthoracic cardioversion (300 J) delivered to stop a VT or VF induced by electrophysiological study. Defibrillation used monophasic waveform. Supraventricular tachyarrhythmias complicated 6% of cardioversions for VT; before cardioversion, all patients were in sinus rhythm. After cardioversion, three patients developed a paroxysmal reentrant supraventricular tachycardia (PSVT), which was stopped by atrial pacing. The remaining patients developed AF that lasted from 3 minutes to 24 hours (n = 4). One patient remained in AF. AF developed after a sinus pause or bradycardia, which was due to the interruption of VT or VF in nine patients or was noted just when VT or VF stopped (n = 10). The analysis of clinical data indicated that all three patients who presented a PSVT had a history of PSVT. Among patients who developed a sinus pause dependent AF, two had a history of AF. Among ten patients who developed AF at the time of cardioversion, three had a history of AF. During follow-up (1-9 years), no patient without a history of AF developed spontaneous AF, but patients with history of tachycardias had arrhythmia recurrences. The mechanism of cardioversion related tachycardias can be a pause related dispersion of atrial refractoriness or an adrenergic reaction induced by VT or VF, factors that precipitate arrhythmias in patients with history of atrial arrhythmias (one third of patients). In conclusion, supraventricular tachyarrhythmia is relatively frequent after external cardioversion for ventricular tachyarrhythmia, has no prognostic significance in patients without previous history of atrial arrhythmias, but in those with history of tachycardias is associated with a high risk of recurrence.

Ventricular flutter induced during electrophysiologic studies in patients with old myocardial infarction: clinical and electrophysiologic predictors, and prognostic significance

INTRODUCTION

Induction of ventricular flutter during electrophysiologic (EP) studies (similar to that of ventricular fibrillation [VF]) often is viewed as a nonspecific response with limited prognostic significance. However, data supporting this dogma originate from patients without previously documented ventricular tachyarrhythmias. We examined the significance of ventricular flutter in patients with and without spontaneous ventricular arrhythmias.

METHODS AND RESULTS

We conducted a cohort study of all patients with myocardial infarction (MI) undergoing EP studies at our institution. Of 344 consecutive patients, 181 had previously documented spontaneous sustained ventricular arrhythmias, 61 had suspected ventricular arrhythmias, and 102 had neither. Ventricular flutter was induced in 65 (19%) of the patients. Left ventricular ejection fraction was highest among patients with inducible VF (35 +/- 13), lowest for patients with inducible sustained monomorphic ventricular tachycardia (SMVT; 27 +/- 9), and intermediate for patients with inducible ventricular flutter (30 +/- 10). Similarly, the coupling intervals needed to induce the arrhythmia were shortest for VF (200 +/- 28 msec), intermediate for ventricular flutter (209 +/- 27 msec), and longest for SMVT (230 +/- 35 msec). During 5 +/- 8 years of follow-up, the risk for ventricular tachycardia/VF was high for patients with SMVT and ventricular flutter and low for patients with inducible VF and noninducible patients (46%, 34%, 17%, and 14%, P < 0.005).

CONCLUSION

Patients with inducible ventricular flutter appear to be "intermediate" between patients with inducible VF and patients with SMVT in terms of clinical and electrophysiologic correlates. However, the prognostic value of inducible ventricular flutter is comparable to that of SMVT.

Utility of current risk stratification tests for predicting major arrhythmic events after myocardial infarction

OBJECTIVES

We surveyed the literature to estimate prediction values for five common tests for risk of major arrhythmic events (MAEs) after myocardial infarction. We then determined feasibility of a staged risk stratification using combinations of noninvasive tests, reserving an electrophysiologic study (EPS) as the final test.

BACKGROUND

Improved approaches are needed for identifying those patients at highest risk for subsequent MAE and candidates for implantable cardioverter-defibrillators.

METHODS

We located 44 reports for which values of MAE incidence and predictive accuracy could be inferred: signal-averaged electrocardiography; heart rate variability; severe ventricular arrhythmia on ambulatory electrocardiography; left ventricular ejection fraction; and EPS. A meta-analysis of reports used receiver-operating characteristic curves to estimate mean values for sensitivity and specificity for each test and 95% confidence limits. We then simulated a clinical situation in which risk was estimated by combining tests in three stages.

RESULTS

Test sensitivities ranged from 42.8% to 62.4%; specificities from 77.4% to 85.8%. A three-stage stratification yielded a low-risk group (80.0% with a two-year MAE risk of 2.9%), a high-risk group (11.8% with a 41.4% risk) and an unstratified group (8.2% with an 8.9% risk equivalent to a two-year incidence of 7.9%).

CONCLUSIONS

Sensitivities and specificities for the five tests were relatively similar. No one test was satisfactory alone for predicting risk. Combinations of tests in stages allowed us to stratify 91.8% of patients as either high-risk or low-risk. These data suggest that a large prospective study to develop a robust prediction model is feasible and desirable.

Long-term reproducibility of ventricular tachycardia induction with electrophysiological testing in patients with coronary heart disease and depressed left ventricular ejection fraction

The Multicenter Automatic Defibrillator Implantation Trial (MADIT) has recently confirmed the role of programmed ventricular stimulation (PVS) to identify the high risk patients of sudden death after myocardial infarction and to prevent this risk. The purpose of this study was to evaluate the long-term reproducibility of PVS in these patients. Thirty patients with coronary heart disease without spontaneous documented sustained ventricular tachycardia (VT) underwent two programmed stimulations in the absence of antiarrhythmic drug treatment between 2 and 6 years (mean 4 years). No patient had a myocardial infarction or intervening cardiac surgery during this period. The protocol of study was similar using up to three extrastimuli in two sites of the right ventricle, delivered in sinus rhythm and driven rhythm (600 ms, 400 ms, respectively). On the first PVS, 17 patients had inducible sustained VT (group I). Thirteen patients did not have inducible VT (group II). On the second PVS all group I patients but one had inducible VT, but the cycle length was significantly modified in 11. In group II, five patients had inducible VT and in the other patients the PVS remained negative. In conclusion, in patients with coronary heart disease, but without documented VT, the long-term reproducibility of PVS was excellent in those with inducible VT (94%); the patients remain at risk of VT and a prophylactic implantable cardioverter defibrillator could be considered. In patients with initially negative study, reproducibility of PVS was lower (61.5%), probably because of the progressive remodeling after myocardial infarction. Therefore, the occurrence of new symptoms in patients with previously negative study requires a second programmed ventricular stimulation.

Predicting the effect of D,L-sotalol on ventricular tachycardia inducibility from the RR variability response

AIM

To find a rapid way of identifying non-responders to D, L-sotalol in patients with ventricular tachycardia.

METHODS

Programmed ventricular stimulation and RR variability were studied in the control state and 10 days after treatment with 160 to 320 mg of D,L-sotalol in 36 consecutive patients with ventricular tachycardia.

RESULTS

In 14 patients (group I) D,L-sotalol suppressed ventricular tachycardia inducibility. In 22 patients (group II) sustained ventricular tachycardia remained inducible during D,L-sotalol treatment. The ventricular tachycardia rate was slowed in eight patients and unchanged or accelerated in 14. At baseline, heart rate variability was similar in both groups. During treatment with D,L-sotalol, variables reflecting parasympathetic activity (pNN50, rMSSD, and high frequency amplitude (HF)) increased in both groups: HF increased from (mean (SD)) 75 (68) to 146 (134) in group I (p < 0.05) and from 60 (49) to 125 (79) in group II (p < 0.05). Other variables were unchanged in group I. In group II, the variables associated with sympathetic activity (coefficient of variance (CV), ratio of low frequency amplitude (LF) to HF) decreased significantly: CV decreased from 13 (4) to 9 (2) (p < 0. 001) and LF/HF from 4.74 (3.02) to 3.00 (2.02) (p < 0.05).

CONCLUSIONS

The beta blocking effect of D,L-sotalol produced a significant improvement over control values in indices of parasympathetic tone in all treated patients. However, the heart rate variability indices related to sympathetic activity were decreased only in non-responders. This effect of D,L-sotalol on heart rate variability could help detect non-responders to the drug and avoid an electrophysiological study.

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

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 indicate the need for nonmedical treatment, such as device therapy.