Which of the following classes of medications maximizes cardiac performance in clients with heart failure by increasing ventricular contractility?
A. Beta-adrenergic blockers
B. Calcium channel blockers
C. Diuretics
D. Inotropic agents
Correct Answer: D. Inotropic agents
Inotropic agents are administered to increase the force of the heart’s contractions, thereby increasing ventricular contractility and ultimately increasing cardiac output. Inotropic agents such as milrinone, digoxin, dopamine, and dobutamine are used to increase the force of cardiac contractions. Intravenous positive inotropic agents should only be used in inpatient settings — and then only in patients who manifest signs and symptoms of low cardiac output syndrome (volume overload with evidence of organ hypoperfusion).
Option A: The catecholamines, epinephrine, and norepinephrine bind to B1 receptors and increase cardiac automaticity as well as conduction velocity. B1 receptors also induce renin release, and this leads to an increase in blood pressure. In contrast, binding to B2 receptors causes relaxation of the smooth muscles along with increased metabolic effects such as glycogenolysis.
Option B: Calcium channel antagonists block the inward movement of calcium by binding to the L-type “long-acting” voltage-gated calcium channels in the heart, vascular smooth muscle, and pancreas. The non-dihydropyridines have inhibitory effects on the sinoatrial (SA), and atrioventricular (AV) nodes are resulting in a slowing of cardiac conduction and contractility.
Option C: They act by diminishing sodium reabsorption at different sites in the nephron, thereby increasing urinary sodium and water losses. The second class of diuretics, sometimes termed aquaretics, instead inhibit water reabsorption by blocking vasopressin receptors along the connecting tubule and collecting duct.
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