A 35-year-old female patient complained of recurrent precordial chest pain referred to her left shoulder which lasted a few minutes and went away upon rest. She also reported a dyspnea after walking about three blocks on level ground. These symptoms had started two years before. She also mentioned a history of rheumatic fever during childhood and a non-specified cardiac surgery in 2001. Physical examination revealed: BP: 160/100 mmHg, PR = 64/min and RR = 28/min; carotid pulsus parvus et tardus; normal jugular venous pulse, sustained apex beat. Cardiac auscultation: regular cardiac rhythm, paradoxical splitting of the second heart sound and a harsh loud (grade 4) meso-systolic murmur heard best at the heart base which radiated to the clavicles but not to the axilla, vanished over the sternum and reappeared faintly at the apex. She had been taking benzathine penicillin 1.200.000 UI IM every three weeks.

Question:
Based on the clinical scenario and the imaging presented, which is the most likely diagnosis?