| Abstract: | Central haemodynamics in the supine and head-up tilted positions were studied in 24 patients with severe postural hypotension with and without supine hypertension. Results were compared with those obtained in eight normotensive and eight untreated hypertensive controls. In the supine position the patients had higher vascular resistances, lower stroke volumes and longer left ventricular ejection time indexes compared to controls, whereas left ventricular ejection fractions did not differ significantly. The patients with supine hypertension had significantly higher vascular resistance compared to those with supine normotension. The highest supine blood pressure levels were found in patients with multiple system atrophy. During tilt, vascular resistance and heart rates were increased and stroke volumes and left ventricular ejection time indexes were decreased in the controls. The patients were unable to increase their vascular resistance, but increased their heart rate and decreased their left ventricular ejection time indexes to a degree similar to the controls. The reductions in stroke volume were smaller in the patients compared to the controls. Changes in haemodynamics in response to head-up tilting did not differ significantly between patients with supine hypertension and supine normotension. It is concluded that patients with postural hypotension have higher supine vascular resistance and are unable to contract peripheral arteries and arterioles during head-up tilting. Contractility of the left ventricle is preserved and the baroreceptors are partially intact. Postural hypotensive patients with supine hypertension differ from those with supine normotension only with respect to supine vascular resistances. |
