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[Comparative hemodynamic effects of 2 vasodilators: dihydralazine and diltiazem in permanent essential arterial
Insights
Diltiazem effectively lowers blood pressure by reducing total peripheral resistance, causing a temporary heart rate increase in hypertensive patients. This study also found diltiazem dilates large arteries.
Area of Science:
- Cardiovascular Pharmacology
- Clinical Hypertension Research
Background:
- Hypertension management requires understanding drug effects on hemodynamics.
- Differentiating the vascular actions of calcium channel blockers is crucial.
Purpose of the Study:
- To compare the hemodynamic and brachial artery effects of diltiazem and dihydralazine in hypertensive patients.
- To elucidate the mechanisms behind diltiazem's antihypertensive action.
Main Methods:
- Pulsed Doppler was used to measure brachial artery hemodynamics (diameter, blood flow velocity, volumic flow).
- Measurements were taken before and after administration of diltiazem and dihydralazine.
- Hemodynamic parameters including blood pressure, total peripheral resistance, cardiac index, and heart rate were analyzed.
Main Results:
- Diltiazem significantly decreased blood pressure and total peripheral resistance, with a transient increase in heart rate and cardiac index.
- Dihydralazine increased cardiac index and heart rate, contrasting with diltiazem's effects.
- Diltiazem administration led to a significant increase in brachial artery diameter, while dihydralazine caused a significant decrease.
Conclusions:
- Diltiazem's antihypertensive effect stems from reduced total peripheral resistance, accompanied by transient baroreflex-mediated tachycardia.
- Diltiazem demonstrates vasodilatory effects on large arteries, in addition to its systemic hemodynamic impacts.
Abstract:
Cardiac hemodynamic and diameter, blood flow velocity, volumic flow of the brachial artery measured by pulsed Doppler, were studied before and after diltiazem administration in comparison with dihydralazine in hypertensive patients. After diltiazem administration, blood pressure and total peripheral resistance significantly decreased (P less than 0.001) while cardiac index and heart rate increased (P less than 0.01). After 25 minutes perfusion cardiac output and heart rate returned toward control values, while blood pressure and total peripheral resistance remained decreased. The result contrasted with those observed after dihydralazine, which induced an increase in cardiac index and heart rate. The caliber of the brachial artery decreased significantly (P less than 0.001) after dihydralazine and increased after diltiazem (P less than 0.01). This study shows that 1). The antihypertensive effect of diltiazem was due to a fall in total peripheral resistance associated with a transient baroreflex mediated tachycardia, and 2) diltiazem dilated also large arteries.