**Core Concept**
In the context of right heart failure, an inotrope is a medication that increases the contractility of the heart muscle, thereby improving cardiac output. Right heart failure is characterized by decreased cardiac output, hypotension, and increased pressures in the right atrium and ventricle. The ideal inotrope for right heart failure should have a positive inotropic effect with minimal or no increase in myocardial oxygen demand.

**Why the Correct Answer is Right**
Milrinone is a phosphodiesterase-3 inhibitor that increases cyclic adenosine monophosphate (cAMP) levels in the cardiac muscle. This leads to increased contractility and relaxation of the heart muscle, thereby improving cardiac output. Milrinone also has vasodilatory properties, which help to reduce pulmonary vascular resistance and improve right ventricular function. Its mechanism of action is unique in that it increases cardiac contractility without significantly increasing heart rate or myocardial oxygen demand.

**Why Each Wrong Option is Incorrect**
**Option A:** Dobutamine is a beta-1 agonist that increases heart rate and contractility, but it also increases myocardial oxygen demand, which can be detrimental in right heart failure.

**Option B:** Digoxin is a cardiac glycoside that increases contractility by inhibiting the sodium-potassium ATPase pump, but it also has negative inotropic effects on the right ventricle and can increase pulmonary vascular resistance.

**Option C:** Dopamine has a dose-dependent effect on the heart, with low doses increasing heart rate and contractility, but high doses can increase myocardial oxygen demand and have negative inotropic effects on the right ventricle.

**Clinical Pearl / High-Yield Fact**
Milrinone is a high-yield fact in the treatment of right heart failure because it is the only inotrope that has been shown to improve survival in patients with acute right heart failure.

**Correct Answer:**
✓ Correct Answer: D. Milrinone