Abstract

Left ventricular systolic pressure, left ventricular diastolic pressure, left ventricular end-diastolic pressure, left ventricular cardiac output, systemic vascular resistance, and central blood volume were specifically measured in seven patients with normal cardiovascular systems before and during the tenth minute of an infusion of l-norepinephrine and the emergence of a `square wave' pattern in the peripheral arterial blood pressure during Valsalva's manœuvre. At that time point the mean left ventricular systolic pressure exceeded the resting level. The mean left ventricular diastolic pressure rose by 6 mm. Hg, and the mean left ventricular end-diastolic pressure rose by 5·5 mm. Hg. The left ventricular output remained unchanged. A reduction in the heart rate of 13 beats/minute was found, and the calculated mean systemic vascular resistance, mean left ventricular stroke volume, and left ventricular stroke work continued to be above resting levels. No change was apparent in the central blood volume. The results indicate that the left ventricular diastolic pressure and left ventricular end-diastolic pressure rise significantly in the course of a prolonged infusion of l-norepinephrine coinciding with left ventricular after-loading. The magnitude of this elevation affects all diastolic pressures passively throughout the lesser circulation, including the central venous pressure. l-Norepinephrine is markedly inotropic when released within the myocardium. In the usual clinical dose and during a period of 10 minutes' infusion its efferent vagal, peripheral, arteriolar constrictor, and left ventricle after-load effects reduce the initial inotropy.