Alterations in Heart Rate Responses and the Effect of Supine and Sitting Recovery Positions on Heart Rate Recovery and Rate Pressure Product Following Submaximal Exercise Test in Patients Undergoing Coronary Artery Bypass Graft Surgery

Abstract

Objectives: The aim of the study was to determine a) Whether there is any change in heart rate responses following submaximal exercise test in patients undergoing CABG b) Is there any effect of recovery position on heart rate recovery and myocardial oxygen consumption following submaximal exercise test in patients undergoing CABG surgery??? Background: The imbalance in the autonomic cardiovascular control has been shown to increase the risk for adverse cardiac events and sudden cardiac death, which has been observed following CABG. Thus, it is important to clinically assess the status of the autonomic nervous system which is a major determinant of cardiovascular health and prognosis. Interventions: The patients were randomly assigned to the two groups: group A and group B. Two six minute walk tests were performed each on the day at 9 a.m. and 1 p.m.; before surgery and following CABG on fourth and seventh postoperative day and the dependent variables were measured. Results: The Peak Heart Rate improved highly significantly from 93.65 + 8.78 per minute on day 0 to 128.24 + 11.94 per minute on day 7 (p<0.0001). The Chronotropic Response Index improved significantly (p<0.0001) from 0.24 + 0.07 to 0.53 + 0.15 from day 0 to day 7. The Six Minute Walk Distance also improved significantly from day 0 to day 7 (p=0.000) from 299.93 + 66.63 m to 380.65 + 109.68 m. The results showed that the HRR increased from 23.06 + 10.43 per minute at first minute to 29.00 + 12.19 per minute at fifth minute, while RPP reduced significantly (p=0.000) from 12005.31 + 2681.83 mmHg/min at first minute to 10232.19 + 1783.22 mmHg/min at fifth minute of recovery. The results show the moderately significant (p=0.00) correlation between the HRR and the peak heart rate, and the HRR, chronotropic response index. Conclusion: The study concluded that there is improvement in the heart rate measures and functional capacity following CABG. The heart rate recovery was also found to vary with different recovery positions and was better in the supine lying position, when compared to sitting position.