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Treatment and post-treatment effects of alpha- versus beta-receptor blockers on left ventricular structure and
H P Schobel1, M Langenfeld, C Gatzka
1Medizinische Klinik IV, University of Erlangen-Nurnberg, Germany.
Insights
Alpha-blockers and beta-blockers equally reduce left ventricular mass in hypertension. Beta-blockers uniquely improve diastolic left ventricular filling, potentially benefiting hypertensive heart disease management.
Area of Science:
- Cardiology
- Pharmacology
- Hypertension Research
Background:
- Essential hypertension is linked to sympathetic nervous system-induced left ventricular mass increase.
- Left ventricular hypertrophy is a key factor in hypertensive heart disease progression.
- Understanding receptor blockade effects on cardiac structure and function is crucial for treatment.
Purpose of the Study:
- To compare the effects of alpha-receptor blockade versus beta-receptor blockade on left ventricular structure and function in essential hypertension.
- To evaluate the impact of bunazosin (alpha-blocker) and metoprolol (beta-blocker) on cardiac remodeling and diastolic function.
- To determine if these receptor blockers differentially affect blood pressure and left ventricular mass.
Main Methods:
- Double-blind, randomized, controlled clinical trial involving 43 patients with mild to moderate essential hypertension.
- Patients received either bunazosin (alpha-blocker) or metoprolol (beta-blocker) for 6 months.
- 24-hour blood pressure and echocardiographic measurements were taken before, during, and after therapy.
Main Results:
- Both bunazosin and metoprolol similarly reduced blood pressure and left ventricular mass.
- Neither drug significantly altered left ventricular systolic function.
- Metoprolol significantly increased diastolic left ventricular filling, unlike bunazosin, attributed to its bradycardiac effect.
Conclusions:
- Alpha-blockers and beta-blockers are equally effective in reducing left ventricular mass in hypertensive patients.
- Beta-blockers enhance diastolic left ventricular filling, offering potential therapeutic benefits for diastolic dysfunction in hypertensive heart disease.
- The observed effects on left ventricular mass and diastolic filling were reversible upon drug discontinuation.
Abstract:
This study was undertaken to compare the effects of alpha-receptor blockade and beta-receptor blockade on left ventricular structure and function in essential hypertension. The increase in left ventricular mass in patients with essential hypertension is at least partly induced by the sympathetic nervous system. We conducted a double-blind, randomized, controlled clinical trial to compare the effects of alpha-blockers and beta-blockers on left ventricular structure and function. Forty-three patients with mild to moderate essential hypertension were randomly allocated to receive antihypertensive therapy with either the alpha-blocker bunazosin (n = 23) or the beta-blocker metoprolol (n = 20). Twenty-four-hour blood pressure measurements and echocardiographic measurements of left ventricular structure and function were performed before therapy, after 6 months of therapy, and 4 weeks after discontinuation of therapy. Bunazosin and metoprolol led to similar reductions in systolic/diastolic blood pressure (-11 +/- 11/-9 +/- 8 mm Hg vs -11 +/- 12/-8 +/- 9 mm Hg, respectively) and left ventricular mass (-25 +/- 42 gm vs -28 +/- 44 gm, respectively) (p = no significant difference, bunazosin vs metoprolol). Neither metoprolol nor bunazosin significantly affected left ventricular systolic function. Diastolic left ventricular filling, however, was increased with beta-blocker medication, as indicated by a decrease in atrial filling fraction (39% +/- 5% to 34% +/- 5%; p < 0.05), but not with the alpha-blocker. The effect of metoprolol resulted from its bradycardiac effect. Four weeks after discontinuation of therapy, blood pressure and left ventricular mass increased to pretreatment levels in both groups similarly. Furthermore, the increase in diastolic filling was lost shortly after withdrawal of metoprolol concomitant with the increase in heart rate. We conclude that alpha-blockers and beta-blockers are equally capable of reducing left ventricular mass in hypertensive patients. beta-Blockers lead to an increase in diastolic left ventricular filling. This effect may be of therapeutic value because diastolic dysfunction may precede systolic dysfunction in hypertensive heart disease.