Different baseline sympathovagal balance and cardiac autonomic responsiveness in ischemic and non-ischemic congestive heart failure.
BACKGROUND: A profound autonomic unbalance is present in heart failure: its correlation with the etiology of the disease has never been investigated. AIMS: We characterized the sympatho-vagal balance and autonomic responsiveness of 42 patients (21 with ischemic heart failure, 21 with idiopathic dilated cardiomyopathy). Patients had comparable NYHA class, ejection fraction, exercise pVO(2), exercise ventilatory response, incidence of beta-blocking treatment. None showed periodic breathing or nocturnal arterial desaturation. METHODS: Heart rate variability was assessed in the time and frequency domain during: (1) 10 min of quiet supine resting and free breathing; (2) 10 min of regular breathing at a frequency of 20 acts/min (=parasympathetic stimulus); and (3) 10 min of active standing (=sympathetic stimulus). The ratio of the low- to high-frequency components of each autospectrum obtained in the frequency domain (LF/HF) was used as an index of sympathovagal balance. RESULTS: Patients with ischemic heart failure had a greater baseline sympathetic activation (higher LF/HF) than those with idiopathic dilated cardiomyopathy, maintaining some parasympathetic responsiveness as well (reduced LF/HF with regular breathing). CONCLUSIONS: There is a distinct autonomic control according to the etiology of heart failure, a finding that may help understanding its pathophysiology, and could be useful in the clinical management of patients.