Correlation of forearm vascular and catecholamine responses of hypertensive patients to baroreceptor stimulation

Fernandez, P.G.; Bolli, P.; Lee, C.

Canadian Journal of Cardiology 6(6): 229-235

1990


ISSN/ISBN: 0828-282X
PMID: 2393834
Document Number: 366610
The relationship between changes in forearm vascular hemodynamics and plasma catecholamine levels during the performance of the Valsalva maneuvre by pretrained hypertensive patients was examined. Eleven mild to moderate hypertensives (supine diastolic pressures from 95 to 105 mmHg), experienced in the consistent performance of the Valsalva maneuvre, had their previous medications withdrawn over a period of one week and were then administered placebo twice daily for the next four weeks. At the end of this period, and 3 h after the last dose of placebo, each patient had a retrograde catheter inserted into an antecubital vein followed by a 30 mimn rest period in the supine position. Blood was sampled for resting catcholamine determination, followed by measurement of resting systolic and diastolic blood pressures together with forearm bloodflow. Each patient then performed the Valsalva maneuvre (40 mmHg, 40 s) with continuous recording of heart rate. Forearm bloodflow was again recorded after 25 s of straining while blood was sampled at the point of bradycardiac after straining. During a duplicate Valsalva maneuvre, systolic and diastolic blood pressures were recorded after 30 s of straining. All patients exhibited the appropriate heart rate responses to the Valsalva maneuvre (resting 76.+-.15 beats/min; tachycardia 101.+-.13, P<0.001; bradycardia (65.+-.18, P<0.01). Forearm bloodflow as reduced (P<0.001) during the maneuvre while mean arterial pressure (P<0.001), forearm vascular resistance (P < 0.001), plasma noradrenaline (P < 0.001) and adrenaline (P<0.05) levels were all increased. Percentage changes in forearm bloodflow and forearm vascular resistance resulting from the maneuvre were correlated (P < 0.05) with the corresponding changes in plasma noradrenaline levels, but there were no correlations between changes in catecholamine levels and either mean arterial pressure or heart rate. The results suggest that activation of baroreceptor reflexes by the Valsalva maneurvre induces increased sympathetic nervous system activity in the peripheral vascular beds, which is reflected in the changes of forearm vascular hemodynamics.

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