HEART-RATE-VARIABILITY IN 2 MODELS OF CARDIAC-HYPERTROPHY IN RATS IN RELATION TO THE NEW MOLECULAR PHENOTYPE

The analysis of heart rate variability (HRV) provides information on n eural control of the heart. We investigated HRV in normal rats and in models of experimental cardiac hypertrophy using the Holter monitoring and peak/trough method. In normal rats, two heart rate oscillations w ith different wavelengths, high frequency (HF) and low frequency (LF) oscillations, were detected. The HF oscillations were insensitive to p ropranolol and suppressed by atropine. The LF oscillations were sensit ive to both antagonists. Thyrotoxicosis resulted in cardiac hypertroph y (+20%) and tachycardia. The HF oscillations were unchanged, whereas LF oscillations were hampered at low heart rate in this group. Aortic stenosis resulted in cardiac hypertrophy (+53%), but heart rate oscill ations were unchanged. The (number x amplitude) product for both types of oscillations correlated with heart rate in controls but not in the thyrotoxicosis or aortic stenosis models. Alterations of HRV in cardi ac hypertrophy occur in rats as in humans. They may reflect the change s in the molecular components of the adrenergic/muscarinic system, whi ch defines the new myocardial phenotype.