In-hospital mobilization after cardiac surgery: investigation of a dose-effect of once- and twice-daily exercise on cardiac autonomic modulation

1  ; Audrey Borghi-Silva 1  Abstract Background: Coronary artery bypass surgery (CABG) implies in impairment of cardiac autonomic modulation (CAM). In-hospital mobilization positively affects CAM; however, it is not known whether higher exercise dosage would provide the same benefits in CAM as lower dosage in patients post-CABG. Aims: To investigate the dose-effect of an exercise inpatient program performed once or twice-daily on cardiac autonomic modulation post-CABG. Design: Prospective trial with a quasi-experimental design. Methods: Thirty patients of both sexes with a diagnosis of coronary heart disease and first-time post-CABG were allocated in a non-random manner into GEX1 (n = 10) and GEX2 (n = 10), composed of patients engaged in one and two daily exercise sessions plus usual care (breathing exercises, education with no systematized mobilization exercise program), respectively; and control group (CG, n = 10), composed of those who only received usual care. Patients underwent a mobilization protocol until discharge, which included a progressive five steps of active-assistive exercises of lower/upper limbs. Heart rate (HR) and R-wave intervals (RRi) were recorded by heart rate monitor at basal condition and discharge time. CAM was assessed by heart rate variability (HRV). Results: At discharge, the higher-dose group (GEX2) showed significant higher values of: parasympathetic (RMSSD: 7.9±1.3 ms vs 4.6±0.4 ms) and overall CAM indexes (STD RR: 7.5±1.1 ms vs 4.8±0.5 ms and TINN (38±6.4 ms vs 23±2.8 ms) compared with CG, respectively. In addition, mean HR (GEX2: 88.1 ±12.3 bpm; GEX1: 79.4±5.7 bpm, CG: 100.4±10.1 bpm) and mean RR (GEX2: 694.0±101.8 bpm; GEX1: 759.1±57.0 bpm, CG: 602.8±59.1 bpm) were different to exercise groups compared to controls regardless dosage. However, there was no significant difference between the exercise groups (GEX1 and GEX2). Conclusions: Regardless dosage, post-CABG patients who engaged in a mobilization-exercise program demonstrated better cardiac autonomic modulation at discharge compared with the control group. The results are encouraging further investigation in the field of in-hospital exercise rehabilitation dosage on cardiac autonomic modulation in a