Abstract
Coronary artery events requiring intervention are associated with depressed cardiac autonomic function. Whether a 6-week cardiac rehabilitation (CR) differs in effectiveness in improving exercise capacity (6MWT), cardiorespiratory function (peakVO2), and autonomic function (HRV) following either cardiac bypass surgery (CABG) or percutaneous coronary revascularization (PCI) is unknown. The current study therefore compared the change in 6MWT and peak VO2 to HRV variables following a 6-week CR program and with patients having either PCI or CABG. Thirty-eight patients, (PCI, n = 22 and CABG, n = 16) participated in the CR program and results for pre and post 6 min walk test (6MWT), peakVO2, and heart rate variability (HRV) were obtained. Our study has shown that a 6 weeks program following either PCI or CABG improves function. However, the effect on post-CABG differs to that of post-PCI patients. The change in distance walked (6MWT, metres) was higher in the CABG (Δ6MWT: 61, p < 0.001) compared to the PCI group (Δ6MWT: 41, p < 0.001). Maximum exercise capacity (peak VO2, ml/kg.min) also changed significantly with a greater change in the CABG group (ΔPCI: 0.7, p < 0.001; ΔCABG: 1.0, p < 0.001) but did not reach normal population values. Although an improvement in HRV parameters was noted for the PCI group, a statistically significant improvement in HRV was observed only in the CABG group for the following; SDNN (ms) (baseline vs. post-rehabilitation (median ± IQR): 31.2 ± 25.6 vs. 51.8 ± 23.1, p < 0.01), RMSSD (19.32 ± 19.9 vs. 42.1 ± 34.2, p < 0.01); LF (ms2) (191 ± 216 vs. 631 ± 693, p < 0.01) and HF (107 ± 201 vs. 449 ± 795.0, p < 0.05). A significant interaction in the PCI group but not in the CABG group was observed using correlation analysis between the 6MWT and peak VO2 with HRV parameters indicating that being healthier that is, a better 6MWT and peak VO2 led to better HRV results but no significant effect of CR in the PCI group. When the results were investigated for baseline 6MWT and peak VO2 effect using a covariate analysis, a significant influence of CR on HRV parameters was retained in the CABG group (p = 0.0072). Our study indicates that a 6-weeks CR program benefits both patient groups in terms of exercise capacity, cardiorespiratory function and autonomic nervous system modulation of heart rate, with CABG patients showing the most improvement. HRV can be a useful additional variable to gauge cardiac function following CR.
Highlights
Percutaneous coronary angioplasty intervention (PCI) and coronary artery bypass grafting (CABG) are effective and established treatments for clinically significant coronary artery disease (CAD) (Eagle et al, 2004; Bravata et al, 2007)
The PCI group consisted of 25 patients and the CABG group of 17 patients
Data from 22 patients in the PCI group and 16 patients in the CABG group were used for the final analysis
Summary
Percutaneous coronary angioplasty intervention (PCI) and coronary artery bypass grafting (CABG) are effective and established treatments for clinically significant coronary artery disease (CAD) (Eagle et al, 2004; Bravata et al, 2007). The long-term survival benefits of cardiac rehabilitation (CR) among patients with CAD have been documented following several large-scale trials and meta-analyses with no direct comparisons between cardiac intervention (CABG vs PCI) or current measures, including the 6-min walk test and peak oxygen volume (6MWT, peak VO2) (Giannuzzi et al, 2003; Taylor et al, 2004; Leon et al, 2005; Suaya et al, 2009). Soumagne reported improvement in functional capacity following CR but did not report direct comparisons between PCI and CABG (Soumagne, 2012). Heart rate variability (HRV) is a valid marker of cardiac autonomic activity and complexity that reflects sympathetic and parasympathetic balance and overall tone (Mäkikallio et al, 2006; Jelinek et al, 2010; McLachlan et al, 2010). Reduced HRV may be associated with abnormal adaptability of the cardiac autonomic nervous system to changes in cardiac pathology and may increase risk of adverse or fatal cardiac events (Kleiger et al, 1987; Quintana et al, 1997; Weber et al, 1999; Jelinek et al, 2010)
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