Determinants of the hemodynamic consequence to sustained ventricular arrhythmias after a single myocardial infarction

Abstract

Patients who have sustained ventricular arrhythmias after myocardial infarction present with either a cardiac arrest or with hemodynamically stable sustained ventricular tachycardia. Recent reports have suggested a different electrophysiologic milieu in these two patient groups and a higher incidence of cardiac arrest in patients with a history of more than one myocardial infarction. No studies have examined patients with only a single previous myocardial infarction. To assess the determinants of the hemodynamic consequence of sustained ventricular arrhythmias more than 3 days after a single myocardial infarction, 82 patients who were resuscitated from arrhythmic cardiac arrest (CA group, 40 patients) or who had hemodynamically stable sustained ventricular tachycardia (No CA group, 42 patients) were examined. Patients in both groups had similar global left ventricular ejection fractions (mean ± SD; 30% ± 12% vs 27% ± 12%; p =NS), proportion of patients with anterior wall infarctions ad compared with the proportion of patients with inferior wall infarctions (55% vs 50%; p =NS), time from infarction to arrhythmia development, severity of coronary artery disease, and the proportion of patients with congestive heart failure or bundle branch block. Patients who presented without cardiac arrest, however, more frequently had left ventricular aneurysms (58% vs 28%; p = 0.005). Sixty-seven patients underwent baseline drug-free electrophysiologic studies. Sustained ventricular tachycardia was induced in 79% of patients in the CA group and 85% of patients in the No CA group ( p =NS). Patients in the CA group had significantly shorter induced ventricular tachycardia cycle lengths (240 ± 40 msec vs 321 ± 86 msec; p < 0.0001) and more frequently had induced polymorphic sustained ventricular arrhythmias (36% vs 11%; p = 0.033). An induced ventricular tachycardia cycle length of less than 260 msec identified patients who had cardiac arrests with a sensitivity of 81%, a specificity of 71%, and a positive predictive value of 73%. No patient with an induced mean ventricular tachycardia cycle length of more than 340 msec had a cardiac arrest. Among patients who have had a single myocardial infarction, the major clinical variable that differentiates those with hemodynamically stable arrhythmias from those with unstable arrhythmias is the presence of a left ventricular aneurysm. Major differences were observed in the electrophysiologic characteristics determined during electrophysiologic study, specifically the ventricular tachycardia cycle length and morphology. Thus patients who have cardiac arrest or hemodynamically stable sustained ventricular tachycardia after a single myocardial infarction appear to fall into two electrophysiologically distinct groups as assessed during electrophysiologic study. The cycle length of induced sustained ventricular tachycardia during electrophysiolgic study may be of prognostic significance.