A 40-year-old male presents with progressive palpitations, shortness of breath, abdominal distension, and lower extremity edema over the past year. Physical exam: Generally well, cardiac dullness on percussion extends bilaterally, weakened apical impulse and S1, 3/6 systolic murmur at the apex, heart rate 100 bpm with regular rhythm, bilateral basal rales/crackles, jugular venous distension, liver palpable 4 cm below the costal margin, spleen not palpable, bilateral lower extremity edema (+), BP 130/90 mmHg. ECG shows complete right bundle branch block. The most likely diagnosis is: