For the last 3 months, a 68-year-old woman has been suffering from pain attacks in the heart that last for 10 minutes. The pain attacks occur in response to the slightest physical exertion. She does not take nitroglycerin because of severe headache. She was repeatedly treated for ischemic heart disease and had a myocardial infarction. Her blood pressure periodically rises to 160/80 mm Hg. ECG shows cicatricial changes in the posterior wall of the left ventricle. Auscultation reveals a systolic murmur over the aorta. What is the most likely diagnosis in this case?