Pharmacological and Parenteral Therapies Q 107

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Which of the following classes of drugs is most widely used in the treatment of cardiomyopathy?

  

     A. Antihypertensive

     B. Beta-adrenergic blockers

     C. Calcium channel blockers

     D. Nitrates

    

    

Correct Answer: B. Beta-adrenergic blockers

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By decreasing the heart rate and contractility, beta-adrenergic blockers improve myocardial filling and cardiac output, which are primary goals in the treatment of cardiomyopathy.

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Option A: Antihypertensives aren’t usually indicated because they would decrease cardiac output in clients who are often already hypotensive. Many antihypertensive drugs have their primary action on systemic vascular resistance. Some of these drugs produce vasodilation by interfering with sympathetic adrenergic vascular tone (sympatholytics) or by blocking the formation of angiotensin II or its vascular receptors.

Option C: Calcium channel blockers are sometimes used for the same reasons as beta-adrenergic blockers; however, they aren’t as effective as beta-adrenergic blockers and cause increased hypotension. These channels are responsible for regulating the influx of calcium into muscle cells, which in turn stimulates smooth muscle contraction and cardiac myocyte contraction. In cardiac nodal tissue, L-type calcium channels play an important role in pacemaker currents, and in phase 0 of the action potentials.

Option D: Nitrates aren’t’ used because of their dilating effects, which would further compromise the myocardium. Nitrates exert their effects by dilating venous vessels, coronary arteries, and small arterioles; its maximal vasodilation is in the venous vessels.

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