A 35-year-old man from Delhi presents with hemoptysis and dyspnea. He has a history of acute rheumatic fever at age 12, treated with penicillin. On examination, he has an irregular pulse, a loud S1, a diastolic murmur at the apex, and a palpable left parasternal heave. Chest X-ray shows a 'double contour' sign and pulmonary edema. Echocardiography reveals severe mitral stenosis (valve area 0.8 cm²), a dilated left atrium (6.5 cm), and a dilated right ventricle with moderate tricuspid regurgitation. What is the pathological basis for the development of tricuspid regurgitation in this patient?