PHENOTYPIC DETERMINANTS OF HEART-RATE-VARIABILITY IN CARDIAC-HYPERTROPHY AND FAILURE

Reduced heart rate variability (HRV) has a strong predictive value in terms of sudden death, as compared to other prognostic criteria, but i t has never been previously studied in experimental models of cardiac hypertrophy and failure. However, it has been quantified in rats using Holter monitoring and the peak and trough method of analysis. In norm al rats, as in humans, short and long oscillations, sensitive, respect ively, to atropine and propranolol were detected Both correlate with h eart rate. Cardiothyrotoxicosis was characterized by tachycardia and i ndependently, by a pronounced alteration in long oscillations. HRV was normal in compensatory cardiac hypertrophy due to aortic stenosis, bu t in this model the normal correlation existing between HRV and heart rate had disappeared. It is suggested that the main determinants of th e above modifications of HRV are the changes in the new myocardial phe notype observed in terms of beta-adrenoceptor and muscarinic densities .