Percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) are widely-used procedures in coronary artery disease (CAD) treatment. Functional disturbances of the autonomic nervous system, illustrated by decreased heart rate variability indices (HRV), are associated with increased risk of cardiac events and total mortality, especially in CAD patients. Parasympathetic activity reduction was observed in patients within 24 hours after PCI. However, this decrease of HRV indices seemed transitory. According to many studies, regular physical activity is one of the factors increasing HRV indices. An improvement of HRV indices after cardiac rehabilitation were observed in PCI patients. CABG, as a more invasive procedure, leads to more profound changes in autonomic regulation of heart function observed for several months or even years in HRV assessment.
The aim of the study was to evaluate the influence of 8-week outpatient comprehensive cardiac rehabilitation program (CR) based on regular aerobic training on HRV indices in CAD patients treated with PCI and CABG.
Methods The study population consisted of 110 male patients with CAD aged 35 to 76 years (mean age 55,13 ± 8,6 years) prospectively and consecutively admitted to an outpatient CR after PCI n = 62, or CABG n = 48. Participants performed cycle ergometer interval training for 45 minutes 3 times a week for 8 weeks. At baseline and after 8 weeks, all patients underwent exercise test and the HRV assessment in the time and frequency domains. Among the time domain parameters, the following were measured:
the mean RR interval (mRR),
the standard deviation of the normal RR interval (SDNN),
square root of the mean square differences of successive RR intervals (rMSSD),
and proportion of the total RR intervals that have differences of successive RR intervals greater than 50 milliseconds (pNN50).
Parameters of the frequency domain were also assessed: low-frequency component (LF: 0.04–0.15 Hz), high-frequency component (HF: 0.15–0.4 Hz) and the LF/HF ratio.
Results HRV indices in CAGB survivals were significantly lower in comparison to patients after PCI at baseline. Significant increases were seen for SDNN, rMSSD, and HF in the CABG group and only in HF component in PCI group after 8 weeks of CR.
Conclusions Eight weeks of cardiac rehabilitation based on regular aerobic training, with respect to the HRV indices, seems to be more effective in patients who underwent CABG than patients after PCI. CR seems to be more beneficial to patients with reduced parasympathetic activity at baseline.