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 pVo₂, exercise ventilatory response, incidence of β-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.