The relationship between anomalies in the autonomous nervous system and left ventricular dysfunction in patients with hypertrophic cardiomyopathy

This study was undertaken to assess autonomic nervous system (ANS) activity and its relation to left ventricular function in 40 patients (mean age: 41 +/- 17 years) with hypertrophic cardiomyopathy (HC), in sinus rhythm, off-drugs. Patients were grouped according to the results of radionuclide angiography: 26 had an ejection fraction > 50% (Group A), whereas 14 had an ejection fraction < or = 50% (Group B). Evaluation of parasympathetic activity showed abnormalities in: heart rate (HR) response during Valsalva (< or = 1.1) in 2 Group A (8%) and 12 Group B (86%) patients (p < 0.001); HR variability during deep breathing (< or = 10 b/min) in 2 Group A (8%) and 14 Group B (100%) patients (p < 0.001); immediate HR response to standing (30:15 < or = 1.0) in 2 Group A (8%) and 6 Group B (43%) patients (p < 0.025). Assessment of sympathetic activity showed abnormalities in: systolic blood pressure fall to standing (> 20 mmHg) in 2 Group B (14%) patients only (NS); diastolic blood pressure response to handgrip (< 10 mmHg) in 4 Group B (29%) patients only (p < 0.025). Thus, in HC: impaired parasympathetic control is common in those patients showing left ventricular dysfunction; concurrent sympathetic abnormality may also occur in this subgroup of patients; ANS dysfunction seems to be merely an epiphenomenon which marks the severity of left ventricular derangement.