RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM, RR-INTERVAL AND BLOOD-PRESSURE VARIABILITY DURING POSTURAL CHANGES AFTER MYOCARDIAL-INFARCTION

Low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.40 Hz) components of heart rate variability have been used to evaluate the a utonomic nervous system. The sympathico-vagal balance as well as the r enin-angiotensin-aldosterone one (RAA) axis are disturbed in the post- acute phase of acute myocardial infarction (AMI). This study examined the relationship between the RAA-axis and spectral indices of the RR-i nterval and blood pressure (BP) variabilities during postural manoeuvr es in the post-AMI period. Power spectral analysis of the RR-interval and BP variabilities was completed from non-invasive beat-to-beat BP m easurements 10-12 days post-AMI, using Fast-Fourier transforms. Concom itantly hormonal changes of the RAA-axis were determined and data were further correlated with the left ventricular ejection fraction. When the patient moved from the lying to the supine position all RAA-axis p arameters significantly increased. Both LF and HF components of total RR-interval variability decreased upon standing, while the LF componen t of systolic and diastolic BP variability increased and HF components remained constant. In the upright position, plasma renin activity (P < 0.01) and angiotensin II (borderline) were inversely related with th e LF component of systolic BP. The aldosterone level was dissociated f rom plasma I renin activity and angiotensin II. The left ventricular e jection fraction was inversely, correlated (P < 0.05) with systolic an d dialstolic BP variabilities and their LF and HF powers. These result s suggest that the renin-angiotensin II system in the post-acute phase of AMI patients treated with aspirin and beta-blocking agents is corr elated with cardiovascular autoregulation during postural manoeuvres.