**Core Concept**
Inotrope agents are used to increase the contractility of the heart muscle, improving cardiac output in conditions like right heart failure secondary to pulmonary hypertension. The optimal inotrope agent should effectively increase right ventricular contractility while minimizing pulmonary vasodilation.

**Why the Correct Answer is Right**
Milrinone is a phosphodiesterase-3 inhibitor that increases cardiac contractility by enhancing calcium release and sensitization. In the context of right heart failure secondary to pulmonary hypertension, milrinone is beneficial because it increases right ventricular contractility without causing significant pulmonary vasodilation, which can worsen pulmonary hypertension. This is in contrast to other inotrope agents like dobutamine, which can cause significant pulmonary vasodilation.

**Why Each Wrong Option is Incorrect**
**Option A:** Dobutamine is a beta-adrenergic agonist that can cause significant pulmonary vasodilation, making it less suitable for right heart failure secondary to pulmonary hypertension.
**Option B:** Digoxin is a cardiac glycoside that increases cardiac contractility by inhibiting the sodium-potassium ATPase pump, but it is not the most effective inotrope agent for right heart failure secondary to pulmonary hypertension.
**Option C:** Levosimendan is a calcium sensitizer that increases cardiac contractility without causing significant pulmonary vasodilation, but it is not typically used as a first-line inotrope agent for right heart failure secondary to pulmonary hypertension.

**Clinical Pearl / High-Yield Fact**
Milrinone is particularly useful in patients with right heart failure secondary to pulmonary hypertension because it can increase cardiac output without causing significant pulmonary vasodilation, thereby reducing the risk of worsening pulmonary hypertension.

**Correct Answer:** C. Milrinone