CARDIAC PARASYMPATHETIC ACTIVITY IN SEVERE UNCOMPLICATED CORONARY-ARTERY DISEASE

Background-Previous studies have suggested that coronary artery diseas e is independently associated with reduced cardiac parasympathetic act ivity, and that this is important in its pathophysiology. These studie s included many patients with complications that might be responsible for the reported autonomic abnormalities. Objective-To measure cardiac parasympathetic activity in patients with uncomplicated coronary arte ry disease. Patients and methods-44 patients of mean (SD) age 56 (8) w ith severe uncomplicated coronary artery disease (symptoms uncontrolle d on maximal medical treatment; > 70% coronary stenosis at angiography ; normal ejection fraction; no evidence of previous infarction, diabet es, or hypertension). Heart rate variability was measured from 24 hour ambulatory electrocardiograms by counting the number of times success ive RR intervals exceeded the preceding RR interval by > 50 ms, a prev iously validated sensitive and specific index of cardiac parasympathet ic activity. Results-Mean (range) of counts were: waking 112 (range 6- 501)/h, sleeping 198 (0-812)/h, and total 3912 (151-14 454)/24 h. Thes e mean results were unremarkable, and < 10% of patients fell below the lower 95% confidence interval for waking, sleeping, or total 24 hour counts in normal people. There was no relation between the severity of coronary artery disease or the use of concurrent antianginal drug tre atment and cardiac parasympathetic activity. Conclusion-In contrast wi th previous reports no evidence of a specific independent association between coronary artery disease and reduced cardiac parasympathetic ac tivity was found. The results of previous studies may reflect the incl usion of patients with complications and not the direct effect of coro nary artery disease itself.