Clinical significance of ventricular tachycardia (3 beats or longer) detected during ambulatory monitoring after myocardial infarction

Abstract

Six-hour ECG recordings were performed every four months during follow-up periods (4-48 months) in 915 patients less than 66 years of age who survived the hospital phase of myocardial infarction. One hundred ninety-nine episodes of ventricular tachycardia (VT) were identified in 66 patients. Most patients (74%) had only one episode of VT. In 47% of the patients, the longest run of VT consisted of three ventricular premature beats in a row. A double set of control patients (N = 132) was assembled by matching each VT patient according to sex, admission date and VT recording date. The VT and control patients were similar in most clinical characteristics. However, VT patients had more severe cardiac disease (P < 0.05) and more evidence of ventricular irritability (P < 0.01) than their matched controls. The mortality rates in the VT and control groups were 16% (11/66) and 8% (11/132), respectively (P < 0.11). The risk of VT patients dying was 2.35 (95% confidence interval 0.82 to 6.77) times that of patients without VT. Life-table analysis of the survival of VT and control patients revealed a 48-month VT survival of 75% compared to 87% in the control group. Among those who died, the age, sex, cause of death, suddenness of death and mechanism of death were similar in the VT and control patients. Within the VT group, those who died had more severe underlying heart disease than the survivors. The occurrence of VT in the posthospital phase of myocardial infarction, while associated with a lower survival rate, does not indicate as much danger as generally assumed.