Hydralazine tachycardia and sympathetic cardiovascular reactivity in normal subjects

Publisher Website
Google Scholar
Abstract
The correlation between hydralazine-induced tachycardia and overall cardiovascular reactivity to sympathetic stimulation was explored in 50 normal subjects. Blood pressure and heart rate changes after standing, immersion of a hand in cold water, the Valsalva maneuver and moderate exercise were compared with pressure and rate responses to 20 mg oral hydralazine. The drug did not modify blood pressure, but increased heart rate, mainly in the standing position. As plotting the magnitude of this response suggested a 2 population distribution, subjects were divided into hyporeactor and hyperreactor groups. Reactivity did not appear to be related to acetylator phenotype. The magnitude of the cardiac response correlated with heart rate responses to standing and to the Valsalva maneuver; when analyzed separately from hyporeactors, correlation was greater among hyperreactors. As the orthostatic and Valsalva responses are reflex in nature apparently hydralazine tachycardia is reflexly induced, that its magnitude may depend on individual baroreceptor sensitivity, which is distributed nonnormally, and that it can be predicted by suitable tests of sympathetic responsiveness.