Copyright © 1998 by the European Society of Cardiology.
Altered autonomic cardiac control in hypertrophic cardiomyopathy
Role of outflow tract obstruction and myocardial hypertrophy
Cardiovascular and Pulmonary Department, University of Pisa, Pisa, Italy
accepted August 5, 1997
Aim The goal of this study was to investigate the role of left ventricular outflow tract obstruction and myocardial hypertrophy on autonomic cardiac function in patients with hypertrophic cardiomyopathy.
Methods and results The sympatho-vagal function was evaluated by spectral analysis of heart rate variability in 28 patients with hypertrophic obstructive cardiomyopathy, 22 patients with hypertrophic non-obstructive cardiomyopathy, 12 with systemic hypertension and left ventricular hypertrophy and 28 healthy subjects. Left ventricular outflow tract pressure gradient in patients with hypertrophic cardiomyopathy was evaluated by echo-Doppler methods and the quantitative assessment of left ventricular hyper-trophy was based on an echocardiographic index. At rest, patients with hypertrophic non-obstructive cardiomyop-athy showed normal spectral patterns, while in patients with hypertrophic obstructive cardiomyopathy and in patients with systemic hypertension we observed, respectively, a significant reduction and increase in the low frequency component relative to the control (P<0·05). During tilt, the physiological increases in the low frequency component, and in the low to high frequency ratio were markedly blunted, or even reverted, only in patients with hypertrophic obstructive cardiomyopathy. In these patients, the heart rate increase during tilt was delayed in comparison to the other groups. Finally, in the hypertrophic obstructive cardiomyopathy group, the impairment of sympathetic activation (lack of increase in the low frequency component during tilt) was significantly correlated to the echocardiographic index of left ventricular hypertrophy (r=–0·800,P<0·001) rather than to the left ventricular outflow tract pressure gradient (r=0·295,P: ns).
Conclusion Among patients with hypertrophic cardiomyopathy, only those with outflow tract obstruction show spectral signs of altered autonomic cardiac control. Within this group, the autonomic dysfunction appears to be correlated to myocardial hypertrophy rather than to left ventricular outflow tract obstruction.
Key Words: Spectral analysis • Hypertrophic cardiomyo-pathy • systemic hypertension • autonomic nervous system.
f1 Correspondence: Ugo Limbruno, MD, Cardiovascular and Pulmonary Department, University of Pisa, Cisanello Hospital, Via Paradisa 2, 56124 Pisa, Italy.
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