Mats Danielson

Carotid baroreceptor function in hypertensive patients

Carotid baroreceptor function has been studied in twenty-five patients with essential hypertension and in ten normotensive control subjects of corresponding age. The carotid baroreceptors were stimulated by increasing the transmural pressure over the carotid arteries by the application of negative pressure in a box enclosing the neck. Stimulation elicited significant decreases in intra-arterial blood pressure, heart rate and cardiac index in both hypertensive and normotensive subjects. Both groups also showed a significant decrease in stroke index and a significant increase in total peripheral vascular resistance index. The response to carotid sinus stimulation did not differ significantly between the two groups. In fourteen of the hypertensive subjects, carotid baroreceptor function was studied after 4 months of saluretic therapy, mefruside, and in nine of these patients after additional treatment with a beta-receptor blocking drug, alprenolol, for another 4 months. Both mefruside and alprenolol induced a significant decrease in mean arterial blood pressure but the response to the carotid baroreceptor stimulation was not significantly altered. The findings indicate that the carotid baroreceptor is re-set to the actual blood pressure level, with little or no change in gain in hypertensive subjects both without and during hypotensive therapy.

Effect of body position on circulatory adaptation to exercise in patients with essential hypertension.

The effect of body position on the central circulatory adaptation to exercise has been studied in ten patients, seven men and three women, with essential hypertension. The subjects were studied at rest and during exercise in sitting and recumbent body positions. With exercise of increasing intensity, the rise of systolic pressure in relation to that of cardiac output was steeper than in a group of normal subjects both in supine and in sitting body position. However, the rise of systemic arterial pressure in relation to cardiac output showed no correlation with resting blood pressure, duration of hypertension, or age. Compared with normal subjects, cardiac output and stroke volume were somewhat lower both in supine and in sitting, though the two groups had the same slope for the increase in cardiac output in relation to oxygen uptake during work. As in healthy subjects, heart rate in relation to oxygen uptake did not differ between supine and sitting positions during work. Thus, in spite of haemodynamic di...