Effects of the reduction of preload on left and right ventricular myocardial velocities analyzed by Doppler tissue echocardiography in healthy subjects.

AIMS: Previous studies using Doppler Tissue Echocardiography (DTE) have suggested that the early-diastolic myocardial velocity behaves as a relatively load-independent index of left ventricular relaxation in patients with cardiac diseases; it is not ascertained if this holds true also in normal human hearts. METHODS AND RESULTS: We assessed the influence of a progressive reduction of preload, obtained by Lower Body Negative Pressure (LBNP), on the diastolic and systolic myocardial waves compared to the inflow patterns estimated in left and right ventricles in nine healthy subjects. LBNP caused a significant decrease in end-diastolic volume, stroke volume and systolic arterial pressure, whilst heart rate increased only at maximum preload reduction; meridional end-systolic stress did not change significantly. The early (E') and late (A') myocardial velocities, at mitral and tricuspid annulus, decreased similarly during lower body suction, so that E'/A' ratio did not change. However, due to reduced early (E) but unchanged late (A) diastolic velocities, the E/A ratio of inflow patterns decreased. Systolic (S') myocardial velocities also decreased during LBNP. LBNP induced greater changes of myocardial diastolic and systolic velocities in the right than in the left ventricle. CONCLUSION: In this study, myocardial E', A' and S' velocities, in both the left and the right ventricle, were significantly affected by preload in healthy subjects. Our results support the usefulness of the E'/A' ratio as a relatively load-independent index of diastolic function.

Sympathetic activation in adipose tissue and skeletal muscle of hypertensive rats.

The activation of the sympathetic nervous system is a common feature of arterial hypertension and other cardiovascular diseases. This activation might be dependent on an altered baroreflex control of vascular resistance of which the inhibitory response on sympathetic activity appears impaired. The aim of the study was to monitor during the natural course of arterial hypertension in spontaneously hypertensive (SHR) and age-matched Wistar Kyoto (WKY) rats (5, 16, 30, and 54 weeks of age) the peripheral sympathetic activity expressed as interstitial norepinephrine (NE) release and as tyrosine hydroxylase (TH) activity, the rate-limiting enzyme of NE synthesis, in the differently baroreflex-controlled subcutaneous adipose tissues and skeletal muscles. Blood pressure and plasma NE in SHR were similar to WKY at 5 weeks of age but increased at all other ages. Body weight was similar in both 5-week-old rats but reduced in SHR at all other ages. The interstitial NE levels were greater in both SHR tissues at all ages as compared with WKY. In adipose tissue of SHR, TH activity was higher at all ages as compared with WKY, whereas TH activity in skeletal muscle was higher only after the development of hypertension. These data show that in both SHR tissues, an increase of interstitial NE release is always present during its lifespan. This suggests that increased sympathetic activation in the SHR model is not specific to baroreflex-controlled tissues such as skeletal muscle but involves also subcutaneous adipose tissue, the sympathetic efferents of which are independent from baroreflexes.