Soru

A 42-year-old woman is evaluated in the clinic due to an 8-month history of progressively worsening shortness of breath. She initially noticed dyspnea only when climbing stairs, but now experiences it while walking on level ground. She has no significant past medical history, takes no medications, and has never smoked. Vital signs show blood pressure of 118/76 mm Hg, heart rate of 88/min, respiratory rate of 18/min, and oxygen saturation of 96% on room air. Jugular venous pulsation is visible 8 cm above the sternal angle. Chest auscultation reveals clear breath sounds bilaterally. Cardiac examination shows a parasternal heave, a loud pulmonic component of the second heart sound (P $_2$), and a faint holosystolic murmur at the lower left sternal border that augments with inspiration. There is trace lower extremity edema. Initial diagnostic testing reveals the following:

- ECG: Right axis deviation and right ventricular hypertrophy.
- Chest X-ray: Enlarged central pulmonary arteries with clear lung parenchyma.
- Transthoracic echocardiogram: Right ventricular dilation with an estimated right ventricular systolic pressure of 65 mm Hg. Left ventricular size and systolic function are normal. There is no significant mitral or aortic valvular disease.
- Pulmonary function tests: Normal spirometry and lung volumes.
- High-resolution chest CT: No evidence of interstitial lung disease.

Which of the following is the most appropriate next step in the diagnostic evaluation of this patient?