Acute Response to Aerobic Exercise on Autonomic Cardiac Control of Patients in Phase III of a Cardiovascular Rehabilitation Program Following Coronary Artery Bypass Grafting

Abstract

Objective

The aim of the present study was to investigate the acute response to aerobic exercise on autonomic cardiac control of patients undergoing coronary artery bypass grafting (CABG).

Methods

The study sample consisted of eight patients (age: 58.6±7.7 years; body mass index: 26.7±3.5 kg.m2) who underwent a successful CABG (no complications during surgery and/or in the following weeks). To assess heart rate variability (HRV), participants remained in a supine position with a 30-degree head elevation for 20 minutes. Electrocardiographic signal (protocol with three derivations) was collected from 600 Hz sample rate to obtain beat-to-beat intervals (R-R interval). This assessment was performed before, after one hour and after 24 hours of the exercise session. All patients underwent a 35 minutes aerobic exercise session (AES) (low-moderate intensity) on the cycle ergometer.

Results

Significant differences were found in the time domain, with positive changes in root mean square of successive RR interval differences (rMSSD) (ms) (parasympathetic component) (one [ P=0.017] and 24 hours [ P=0.007] post-session). In the frequency domain, we found a significant difference in high frequency (HF) (ms2) (parasympathetic component) (one hour [ P=0.048] post-session). The low frequency (LF)/HF ratio (sympathetic and parasympathetic components with a predominance of the sympathetic component) reached statistical significance only 24 hours ( P=0.018) post-session. Additionally, the largest effect size was observed only for the LF/HF ratio at one ( d=-0.8) and 24 hours ( d=-1.3) after one AES.

Conclusion

The practice of (acute) aerobic exercise improved autonomic cardiac control in patients undergoing CABG.