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Autonomic mechanisms may have an important role in the clinical presentation of acute coronary occlusion. This research was designed to evaluate the effect of preocclusion stenosis severity on the immediate autonomic heart rate (HR) responses to a subsequent acute occlusion of the coronary artery. HR and its variability in the time and frequency domains were analyzed in patients with mild to moderate (< or = 85%) (group 1, n = 19) and severe (> 85%) (group 2, n = 18) left anterior descending coronary artery stenosis immediately before and during balloon occlusion (mean 108 seconds). The ranges of nonspecific responses were determined by analyzing HR reactions in a control group (n = 13) with no ischemia during balloon inflation of a totally occluded coronary artery. An abnormal increase in HR variability and/or bradycardia as a sign of vagal activation occurred in 6 patients (32%) in group 1 and in 3 patients (17%) in group 2. A significant decrease in HR variability or tachycardia, or both, was observed in 5 patients (26%) in group 1, but in none of the patients in group 2. Compared with the control group, the balloon occlusion of mild to moderate stenosis caused abnormal HR reactions more often than did occlusion of tight stenosis (58% vs 17%, p < 0.05). Balloon occlusions in group 1 caused chest pain (p < 0.01), ST-segment changes (p < 0.001), and narrowing of pulse pressure (p < 0.05) more often than did occlusions of severe stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Signs of sympathetic activation are frequent during the early hours of anterior wall acute myocardial infarction, whereas parasympathetic reflexes predominate in inferior wall acute myocardial infarction. To assess the immediate autonomic responses to acute coronary occlusion, the high-frequency power and root-mean-square successive difference, frequency and time domain measures of heart rate (HR) variability were analyzed in 73 cases of significant (50 to 95%) coronary artery stenosis immediately before and during balloon occlusion (mean 99 seconds). The range of nonspecific changes was formed on the basis of a control group with no ischemia during dilatations of 16 totally occluded coronary arteries. Balloon occlusion of the left anterior descending artery (n = 35) caused an abnormal increase in the measures of HR variability as a sign of vagal activation in 8 patients (23%), and a significant decrease in HR variability in 4 (11%). Occlusion of the left circumflex artery (n = 19) caused an increase in HR variability in 5 patients (26%), and a decrease in 2 (11%). Right coronary artery occlusion (n = 19) caused an increase in HR variability in 5 patients (26%) and a decrease in 4 (21%). Thus, coronary occlusion causes immediate changes in HR variability in greater than one third of patients with coronary artery disease. The direction of these initial HR variability changes cannot be predicted by the site of coronary occlusion.

Reduced heart rate (HR) variability is associated with increased risk of cardiac arrest in patients with coronary artery disease. In this study, the power spectral components of HR variability and their circadian pattern in 22 survivors of out-of-hospital cardiac arrest not associated with acute myocardial infarction were compared with those of 22 control patients matched with respect to age, sex, previous myocardial infarction, ejection fraction and number of diseased coronary arteries. Survivors of cardiac arrest had significantly lower 24-hour average standard deviation of RR intervals than control patients (29 +/- 10 vs 51 +/- 15 ms, p less than 0.001), and the 24-hour mean high frequency spectral area was also lower in survivors of cardiac arrest than in control patients (13 +/- 7 ms2 x 10 vs 28 +/- 14 ms2 x 10, p less than 0.01). In a single cosinor analysis, a significant circadian rhythm of HR variability was observed in both groups with the acrophase of standard deviation of RR intervals and high-frequency spectral area occurring between 3 and 6 A.M. which was followed by an abrupt decrease in HR variability after arousal. The amplitude of the circadian rhythm of HR variability did not differ between the groups. Thus, HR variability is reduced in survivors of cardiac arrest but its circadian rhythm is maintained so that a very low HR variability is observed in the morning after awakening, corresponding to the time period at which the incidence of sudden cardiac death is highest.

The predictive value of a postoperative exercise test in terms of cardiac events after coronary artery bypass grafting (CABG) was prospectively studied in 231 consecutive patients. During a 5-year follow-up there were 28 cardiac events (12%), of which 15 were cardiac deaths (13 sudden), and 13 were nonfatal myocardial infarctions. There was no difference in the rate of graft patency between groups with and without cardiac events, but ejection fraction was lower in patients with than without events (51 +/- 16% vs 58 +/- 10%; p less than 0.05). Duration of the exercise test was shorter, and maximal work load was lower in patients with cardiac events (p less than 0.05 for both). The prevalence of greater than or equal to 1 mm ST-segment depression was 22% (symptomatic in 25%, and silent in 75%) and did not differ between groups with and without cardiac events. After adjustment for prognostic variables using the proportional hazards method, diuretic treatment (p = 0.007) and a low postoperative ejection fraction (p = 0.04) remained significant for predicting the risk of cardiac events within 5 years of CABG, but exercise duration and work load did not have any significant predictive value. Thus, the predictive value of a postoperative exercise test is limited, and signs of impaired left ventricular function are of greater significance for the 5-year prognosis after CABG than are those of myocardial ischemia.

Exercise-induced ventricular arrhythmias occur often after coronary artery bypass grafting (CABG), but their prognostic significance is unknown. Two hundred patients examined by exercise electrocardiography and cardiac catheterization (including left ventriculography, bypass graft and native coronary artery angiography) before and 3 months after CABG were prospectively followed up. Exercise-induced ventricular arrhythmias occurred more often after (49 of 200 patients, 24.5%) than before (32 of 200 patients, 16.0%) CABG (p less than 0.05). There were no differences between the patients with and without ventricular arrhythmias in the prevalence of graft patency (79 vs 80%) or the postoperative ejection fraction (57 +/- 9 vs 57 +/- 12%). Ten cardiac deaths occurred during the mean follow-up time of 61 +/- 19 months, 8 of which were witnessed sudden cardiac deaths. All cardiac deaths occurred in patients who did not have exercise-induced ventricular arrhythmias after CABG. The postoperative ejection fraction was lower in the cardiac death patients (42 +/- 16%) than in the survivors (58 +/- 10%) (p less than 0.01). No other clinical or angiographic variable predicted the occurrence of cardiac death. Thus, the prevalence of exercise-induced ventricular arrhythmias increases after CABG, but the occurrence of ventricular arrhythmias does not indicate an increased risk of cardiac death.

The left ventricular (LV) response to isometric exercise was evaluated in 20 patients who performed handgrip exercise tests before and 3 months after coronary artery bypass grafting. Preoperative LV ejection fraction (EF) decreased during the handgrip test from 0.57 +/- 0.08 to 0.49 +/- 0.09 (p less than 0.001); the ratio between the LV peak systolic pressure (PSP) and end-systolic volume index (ESVI) did not change. In 12 patients with patent grafts, the LVEF after operation did not change (0.54 +/- 0.06 at rest and 0.56 +/- 0.06 during handgrip exercise) and PSP/ESVI ratio increased from 4.5 +/- 1.5 to 5.6 +/- 2.1 mm Hg/ml X m-2 (p less than 0.001) during exercise. In 8 patients with occluded grafts, the LVEF after operation decreased from 0.56 +/- 0.10 to 0.48 +/- 0.06 (p less than 0.02), whereas PSP/ESVI did not change during handgrip exercise. Thus, the LV response to isometric handgrip exercise appears to improve after coronary artery bypass grafting in patients with patent grafts, but not in patients with 1 or more occluded grafts.