PURPOSE: Heart rate variability (HRV) indices are powerful independent prognostic factors of cardiovascular events and all cause mortality in patients with chronic heart failure (CHF). This study evaluates the influence of lifestyle on HRV in CHF patients.
METHODS: Thirty-nine CHF patients (33 men, ischemic/dilated cardiomyopathy (18/21), 52.4 +/- 11.2 yr, NYHA I to III, LVEF 33.4 +/- 5.1%) filled out a physical activity questionnaire providing an individual complete qualitative and quantitative picture of their physical activity and daily energy expenditure (PAEE/DEE) corrected for age, weight, severity of the condition and autonomy. Frequency and time domain indices of HRV were calculated from ECG Holter recordings on a typical weekday. Nighttime indices were calculated in order to avoid the confounding factor of physical activity that might alter 24-h frequency analysis of HRV.
RESULTS: DEE was significantly different between classes I and II and classes I and III (P = 0.01 both) patients. Time spent in activities above 3 METs decreased significantly with the severity of the condition. Global and parasympathetic indices of 24-h HRV analysis were correlated to DEE and PAEE (Ptot24h = 78.80*PAEE (J x min x kg) -1061.80, R = 0.72, P < 0.0001). Multiple regression analysis revealed that PAEE was the sole independent factor on established HRV prognostic indices (P < 0.05) and especially within PAEE dimensions, only activities above 3 METs were correlated with established prognostic HRV indices (P < 0.05).
CONCLUSION: These results indicate that rather than total DEE, moderate to intensive physical activity may counteract the decline in HRV with chronic heart disease. This may be linked to longer time spent in higher intensity activities, and not to total activity time.