Persistent sympathoexcitation long after submaximal exercise in subjects with and without coronary artery disease

Abstract

There is an increased risk of cardiac events after exercise, which may, in part, be mediated by the sympathoexcitation that accompanies exercise. The duration and extent of this sympathoexcitation following moderate exercise is unknown, particularly in those with coronary artery disease (CAD). Twenty control subjects (mean age, 51 years) and 89 subjects with CAD (mean age, 58 years) underwent two 16-min bicycle exercise sessions followed by 30-45 min of recovery. Session 1 was performed under physiological conditions to peak workloads of 50-100 W. In session 2, parasympathetic blockade with atropine (0.04 mg/kg) was achieved at end exercise at the same workload as session 1. RR interval was continually recorded, and plasma catecholamines were measured at rest and selected times during exercise and recovery. Parasympathetic effect, measured as the difference in RR interval with and without atropine, did not differ between controls and CAD subjects in recovery. At 30 and 45 min of recovery, RR intervals were 12% and 9%, respectively, shorter than at rest. At 30 and 45 min of recovery, plasma norepinephrine levels were 15% and 12%, respectively, higher than at rest. A brief period of moderate exercise is associated with a prolonged period of sympathoexcitation extending >45 min into recovery and is quantitatively similar among control subjects and subjects with CAD, with or without left ventricular dysfunction. Parasympathetic reactivation occurs early after exercise and is also surprisingly quantitatively similar in controls and subjects with CAD. The role of these autonomic changes in precipitating cardiac events requires further evaluation.

Recovery of Heart Rate Variability and Ventricular Repolarization Indices Following Exercise

“…The heart rate response to exercise and recovery is shown in Table 2. As previously reported [25], all groups had persistent elevation of the heart rate at 30 and 45 minutes of recovery as compared to the resting heart rate (p<0.01 and p<0.03, respectively).…”

“…While evaluation of heart rate changes and plasma catecholamine changes in the post-exercise recovery period did not identify differences among the study groups [25], there were differences in the recovery HRV findings among the group. The prognostic significance of HRV after exercise has not been studied, but represents an intriguing possibility based on the present findings.…”

“…The study protocol has been previously described in detail [25]. Briefly, a control group of 20 subjects without cardiac disease were studied and a group of 89 subjects with coronary artery disease (CAD) were studied.…”

“…Furthermore, heart rate recovery, an index of changing autonomic tone in early recovery has been shown to predict cardiac mortality [7-12]. We have demonstrated that sympathoexcitation following a moderate period of exertion can be detected up to 45 minutes following the period of exertion [13] while parasympathetic reactivation is complete within a couple minutes. As sympathoexcitation may precipitate ventricular tachyarrhythmias [14, 15] and as abnormal heart rate variability [16-18] and abnormalities in cardiac repolarization [19-24] are associated with cardiac mortality, the present study hypothesized that there would be persistent abnormalities in heart rate variability and cardiac repolarization lasting at least 45 minutes into the post-exercise recovery period.…”

Improvements in Heart Rate Recovery Among Women After Cardiac Rehabilitation Completion

“…Our data concur with the view that the intensity of PNS reactivation steadily increases further until 4 minutes into recovery and remains relatively constant thereafter. 8 In patients with and without CHD, Wang et al 68 found that PNS effects on HR reached a peak about 2 minutes into recovery from exercise, whereas SNS effects dissipated more slowly, with significant increases in plasma catecholamines and HR even 45 minutes after exercise. Johnson and Goldberger 9 suggest that late HRR reflects withdrawal of SNS drive of exercise, with lower HRR indicating more persistent SNS excitation.…”