No abstract

Experimental studies have shown that among dogs with a healed myocardial infarction, depressed baroreflex sensitivity (BRS) identifies a subgroup at higher risk for sudden death. We have examined the relation among BRS, several clinical cardiovascular variables, and subsequent mortality in 78 patients below the age of 65 years who have had a first myocardial infarction. BRS was assessed by calculating the regression line relating phenylephrine-induced increases in systolic blood pressure to the attendant changes in the RR interval. A reduced BRS primarily reflects an impairment in the vagal efferent component of the baroreceptor reflexes. The BRS of the entire population was 7.8 +/- 4.9 msec/mm Hg. BRS was lower among patients with an inferior myocardial infarction (6.1 +/- 3.3 vs. 8.9 +/- 5.8 msec/mm Hg, p = 0.03), with a three- versus a one-vessel disease (4.8 +/- 2.7 vs. 7.1 +/- 3.1 msec/mm Hg, p = 0.04), and with episodes of ventricular tachycardia (5.1 +/- 3.0 vs. 8.3 +/- 5.1, p = 0.03). There was no correlation between BRS and left ventricular ejection fraction or with mean pulmonary capillary wedge pressure at peak exercise, but a correlation (r = 0.35, p less than 0.001) was present with exercise tolerance. During the 24 months mean follow-up period, there were six cardiovascular deaths (7.6%), and four were sudden.(ABSTRACT TRUNCATED AT 250 WORDS)

5%); p = 0.0004), the plaque substrate for thrombosis was erosion. Healed infarcts were found in 37.5% of men v 22% of women (p = 0.01). Heart rupture was more common in women than in men (22% v 10.5%, p = 0.01). The distribution of infarcts, thrombus location, heart rupture, and healed infarcts was similar in cases of plaque rupture and plaque erosion. Conclusions-Plaque erosion is an important substrate for coronary thrombosis in patients dying of acute myocardial infarction. Its prevalence is significantly higher in women than in men. (Heart 1999;82:269-272)

Background-Despite the rational expectation for a survival benefit produced by exercise training among post-myocardial infarction (MI) patients, direct evidence remains elusive. Clinically, changes in autonomic balance toward lower vagal activity have consistently been associated with increased mortality risk; conversely, among both control and post-MI dogs, exercise training improved vagal reflexes and prevented sudden death. Accordingly, we tested the hypothesis that exercise training, if accompanied by a shift toward increased vagal activity of an autonomic marker such as baroreflex sensitivity (BRS), could reduce mortality in post-MI patients. Methods and Results-Ninety-five consecutive male patients surviving a first uncomplicated MI were randomly assigned to a 4-week endurance training period or to no training. Age (51Ϯ8 versus 52Ϯ8 years), site of MI (anterior 41% versus 43%), left ventricular ejection fraction (52Ϯ13 versus 51Ϯ14%), and BRS (7.9Ϯ5.4 versus 7.9Ϯ3.4 ms/mm Hg) did not differ between the two groups. After 4 weeks, BRS improved by 26% (Pϭ0.04) in trained patients, whereas it did not change in nontrained patients. During a 10-year follow-up, cardiac mortality among the 16 trained patients who had an exercise-induced increase in BRS Ն3 ms/mm Hg (responders) was strikingly lower compared with that of the trained patients without such a BRS increase (nonresponders) and that of the nontrained patients (0 of