A 48-year-old female presents with progressive exertional dyspnea and syncope. Right-heart catheterization confirms a mean pulmonary arterial pressure (mPAP) of 38 mmHg at rest with a normal pulmonary capillary wedge pressure (PCWP) of 11 mmHg. Which targeted vasodilatory medication class acts by inhibiting the enzyme responsible for degrading cyclic guanosine monophosphate (cGMP)?

Answer and explanation

Correct answer: A. Phosphodiesterase-5 Inhibitors

  1. Step 1: Pulmonary arterial hypertension (mPAP > 20 mmHg with PCWP <= 15 mmHg) is managed with pathway-targeted therapies.
  2. Step 2: Phosphodiesterase-5 (PDE-5) inhibitors (such as sildenafil and tadalafil) prevent the degradation of cGMP, enhancing nitric oxide-mediated pulmonary vascular smooth muscle relaxation and vasodilation.
Answer
Phosphodiesterase-5 (PDE-5) Inhibitors (e.g., Sildenafil).
Why not the others: 'Endothelin Receptor Antagonists' competitively block ETA and ETB receptors, blunting endothelin-1 vasoconstriction; 'Prostacyclin Analogues' stimulate prostacyclin receptors and adenylate cyclase to raise cAMP; 'Calcium Channel Blockers' block L-type calcium channels, used only in rare vasoreactive responders.

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