Role of programmed electrical stimulation of the heart in risk stratification post-myocardial infarction

Programmed electrical stimulation (PES) of the heart was evaluated as a method of identifying patients at risk of sudden death post-myocardial infarction (post-MI). Eighty-four patients (mean age, 56 +/- 10 years) underwent PES 6 to 8 weeks post-MI. PES was performed at the right ventricular apex at twice diastolic threshold. Prior to stimulation patients were studied with exercise stress testing, 24-hour Holter monitoring and radionuclide ejection fraction. The patients were placed into two groups, according to their responses to electrical stimulation. Group 1:65 patients in whom no arrhythmias were induced or who had repetitive responses that lasted less than six cycles; Group 2:19 patients in whom ventricular tachycardia was induced. At the end of follow-up (20 +/- 9 months) six patients from Group 1 had died. Complex ventricular ectopy and ventricular tachycardia were more frequently detected on Holter in Group 2 (9/19) than in Group 1 (14/65) (p less than 0.03). The results of exercise testing and radionuclide ejection fraction did not correlate with the response to PES. However all but one of the patients who died had a left ventricular ejection fraction (LVEF) under 40% and four out of six patients had ventricular tachycardia on Holter monitor. We draw the conclusion that PES did not contribute to the identification of high-risk patients post-MI, as none of the 19 patients in whom ventricular tachycardia was induced died during follow-up. In addition, high-risk patients were characterized by poor ventricular function and complex ventricular arrhythmias on Holter recording.