INTRODUCTION: Since altered heart rate (HR) fluctuations provide prognostic information in heart failure, we examined the associations between HR dynamics, myocardial efficiency and perfusion, among patients with dilated cardiomyopathy. METHODS: Sixteen patients with dilated cardiomyopathy were enrolled. Patients received supervised strength and aerobic training for 5 months (n = 9) or standard care (n = 7). The short-term scaling exponent (alpha(1)) and frequency domain measures of HR behavior were assessed at baseline and after 5 months of intervention. The left ventricular (LV) function measured using echocardiography and oxidative metabolism measured using positron emission tomography (PET) and [(11)C]-acetate were used to estimate the myocardial efficiency. RESULTS: Short-term fractal exponent alpha(1) correlated significantly with LV myocardial efficiency (r = 0.77, p = 0.002) at baseline. After the intervention period, the majority of patients showed improved myocardial efficiency and small or marked change in HR dynamics toward the natural fractal-like organization (alpha(1) value close 1). Parallel change in fractal properties of HR and myocardial efficiency after intervention was observed in 78% of the patients. Intervention had no significant effect on any other HR fluctuation indices. CONCLUSIONS: The present study suggests that short-term fractal scaling exponent alpha(1), an important prognostic marker in heart failure, is related to LV myocardial efficiency.
INTRODUCTION: Since altered heart rate (HR) fluctuations provide prognostic information in heart failure, we examined the associations between HR dynamics, myocardial efficiency and perfusion, among patients with dilated cardiomyopathy. METHODS: Sixteen patients with dilated cardiomyopathy were enrolled. Patients received supervised strength and aerobic training for 5 months (n = 9) or standard care (n = 7). The short-term scaling exponent (alpha(1)) and frequency domain measures of HR behavior were assessed at baseline and after 5 months of intervention. The left ventricular (LV) function measured using echocardiography and oxidative metabolism measured using positron emission tomography (PET) and [(11)C]-acetate were used to estimate the myocardial efficiency. RESULTS: Short-term fractal exponent alpha(1) correlated significantly with LV myocardial efficiency (r = 0.77, p = 0.002) at baseline. After the intervention period, the majority of patients showed improved myocardial efficiency and small or marked change in HR dynamics toward the natural fractal-like organization (alpha(1) value close 1). Parallel change in fractal properties of HR and myocardial efficiency after intervention was observed in 78% of the patients. Intervention had no significant effect on any other HR fluctuation indices. CONCLUSIONS: The present study suggests that short-term fractal scaling exponent alpha(1), an important prognostic marker in heart failure, is related to LV myocardial efficiency.
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