No abstract

Peripheral haemodynamics was studied in healthy volunteers by strain gauge plethysmography after administration of ibopamine (IB), diisobutyric ester of N-methyl-dopamine, an orally active dopaminergic agonist. Seven subjects received a single oral dose of ibopamine of 150 mg and 6 received a daily dose of 150 mg (50 mg t.i.d.) for 5 consecutive days. Arterial resting blood flow and venous capacity increased and peripheral resistance decreased significantly. Six further subjects were then studied; 3 h after an oral dose of ibopamine 150 mg, the parenteral administration of Sulpiride 50 mg, a specific vascular dopaminergic antagonist, was found significantly to counteract its peripheral activity. Heart rate and arterial blood pressure were never affected and tolerability was good.

The purpose was to assess age-related circadian changes of blood pressure profile (BPP) employing a truncated Fourier series with four harmonics (tFs) in patients with essential hypertension. The study was performed on 32 patients with essential hypertension divided in two groups: (A) 15 patients younger than 55 years and (B) 17 patients older than 60 years. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were monitored every 20 minutes for 24 h with a noninvasive portable device (SpaceLabs 90202). To evaluate the existence of SBP and DBP circadian rhythms a one-sample runs-test was performed and the mesor, amplitude, and acrophase from the overall curve of each patient were obtained by tFs. In both groups, SBP and DBP profiles showed a first peak in the late morning and a second peak in the early evening around the same hours. The two peaks in the SBP profile were higher and the two peaks in the DBP profile were lower in older patients than in younger ones (p < .01, p < .05, p < .3, p < .05). The truncated Fourier series with four harmonics evidences different age-related BP profiles characterized by two peaks with higher SBP and lower DBP in elderly patients. These changes of BPP are in accordance with the reported higher risk of cardiovascular events observed around the same hours.

Hypertension and diabetes show arteriolar structural changes of similar gravity. Age does play a role in hypertension but a smaller one than that played by blood pressure. In hypertension and diabetes the lack of significance of the contribution of age to the correlation between minimal vascular resistance and pressure could be ascribed to other neurohumoral factors. These factors play a much more important role in diabetes; where neither blood pressure nor age show any correlation with high vascular resistance.

SUMMARYThe third heart sound (S3) is often present in children and adolescents but is not present in most adults. Applying at the left ventricle a mathematical model, the mechanism of the disappearance of S3 was studied employing the frequency analysis of the sound and echocardiographic data. The existence of a significant correlation between the spectrum energy of S3 and the diameter and thickness of the left ventricle at the moment of S3 in 25 healthy subjects (aged 217 years) allowed us to interpret the origin of S3 based on a viscoelastic oscillating system. Once the left ventricle starts vibrating it behaves as a simple physical model composed of a mass (m), a spring (k) and a viscous element. The abrupt deceleration of the blood mass (m) against the left ventricular walls (k) triggers the vibration of the system according to the equation Fd=1/24k/m , where Fd is the natural damped frequency and is the damping factor. The equation shows that the vibrating system can oscillate only if is <1. During the growth of the individual the increased myocardial mass may lead to augmented viscous forces causing a gradual increase in until the system becomes overdamped and consequently unable to vibrate causing the disappearance of S3. (Jpn Heart J 1996; 37: 215-226) Key words:Third heart sound Spectral analysis Echocardiography Phonocardiography HE third heart sound (S3) consists of a group of low frequency vibrations, audible or recordable at the point of the maximal apical impulse during early diastole in a high percentage of normal children and healthy young adults; its prevalence characteristically tends to decrease with increasing age.1)Various theories have been proposed to explain both the genesis of S3 and its disappearance with aging.2-6) We already approached the problem of the gen-