[Limits of mental stress as an instrument for evaluative screening in recent myocardial infarction]

In order to investigate whether stressors could induce ventricular arrhythmias or myocardial ischemia in the postinfarction period, 130 patients with recent myocardial infarction (1-2 months after the acute episode), after drug washout, were exposed to two stressors in a random sequence. Mental arithmetic and Sacks test (30 incomplete sentences with high emotional content) were used for 3 min, followed by 5 min recovery. Ninety % of the patients underwent an exercise test and 73% a 24 hour ambulatory monitoring in the same conditions. Ventricular arrhythmias occurred respectively in 21%, 26% and 86% of the patients during mental stress, exercise test and ambulatory ECG monitoring. The arrhythmias score (Italian Lown modified classification) was greater than or equal to 40 in 2% of the patients during mental stress and in 39% in the ambulatory ECG. Only 3 patients (2.3%) showed ST-segment depression greater than or equal to 1mm during mental stress vs. 30.7% during exercise. The double product threshold for ST-segment shift was reached or exceeded during mental stress by 22% of the patients. The increments in heart rate and blood pressure were independent from each other, and similar in the two stress tests. Only the heart rate was slightly higher during mental arithmetic (p less than 0.01). In conclusion, the utilized short-lasting stressors were poorly effective in inducing myocardial ischemia and ventricular arrhythmias in patients with recent myocardial infarction. It is suggested to avoid the generalization of these results to patients with different pathophysiological conditions, taking on account the methodological limits of the study.