Valvular Heart Disease USMLE Step 1 Practice Question

A 73-year-old man with a 15-year history of hypertension and stage 3 chronic kidney disease presents to the clinic with progressive dyspnea on exertion and bilateral lower extremity edema over the past 3 months. His wife notes he has become increasingly fatigued. Vital signs are: BP 162/96 mmHg, HR 102 bpm, RR 22, SpO2 97% on room air. On physical examination, jugular venous pressure is elevated at 10 cm H2O, the liver is palpable 4 cm below the costal margin and tender to palpation, and there is bilateral pitting ankle edema. Cardiac auscultation reveals a holosystolic murmur at the left lower sternal border that increases in intensity with inspiration. Chest X-ray shows pulmonary edema and cardiomegaly. Transthoracic echocardiography demonstrates severe right ventricular dilatation (RV diameter 5.2 cm) with an ejection fraction of 35%, global hypokinesis, and severe tricuspid regurgitation with an estimated right atrial pressure of 18 mmHg. BNP is 520 pg/mL. Blood cultures are negative, and there is no history of intravenous drug use or recent instrumentation. Which of the following best explains the pathophysiology of this patient's murmur?