A patient with acute decompensated HFrEF who is already receiving maximal oral beta-blockade requires inotropic support for low-output states. Which intravenous agent acts independently of the beta receptor and is therefore appropriate here?

• A Dobutamine
• B Isoproterenol
• C Norepinephrine
• D Milrinone ✓

Explanation

Milrinone inhibits phosphodiesterase type 3 in cardiac myocytes, preventing cAMP breakdown and raising intracellular calcium independently of beta-adrenergic receptors. This makes it effective even when beta receptors are occupied by antagonists or desensitized, and it also produces vasodilation (an inodilator profile), lowering filling pressures. Dobutamine and isoproterenol are direct beta-1 agonists whose effects are blunted by concomitant beta-blockade. Norepinephrine works through alpha-1 vasoconstriction and raises afterload unfavorably.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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