Which beta1 agonist is used for short-term treatment of heart failure?

• A. Isoproterenol
• B. Norepinephrine
• C. Dobutamine
• D. Pralidoxime

Answer: (C)

The key idea is boosting heart muscle contractility without markedly increasing afterload or causing excessive heart rate. Dobutamine fits this well because it acts mainly on beta-1 receptors in the heart, enhancing intracellular cAMP and calcium in cardiac myocytes to increase contractility (inotropy). This raises stroke volume and cardiac output, which is exactly what’s needed in short-term heart failure management. At the same time, it has only mild beta-2 effects and minimal alpha effects, so it provides a net benefit with less vasoconstriction and less rise in afterload compared with other agents.

Isoproterenol, a nonselective beta agonist, increases heart rate and contractility but can cause significant vasodilation and tachyarrhythmias, which can worsen perfusion in heart failure. Norepinephrine mainly drives alpha-adrenergic vasoconstriction with some beta-1 activity; the increased afterload can be hard on a failing heart. Pralidoxime is an antidote for organophosphate poisoning and has no role as a heart-failure inotrope.