Brief Answer: No immediate threat; aspirin can be substituted Detailed Answer: Hello sir and welcome. Thank you for writing to us. In my opinion the exhaustion and difficulty in climbing stairs could be related to the cardiac changes that have been observed. The LV (left ventricular; which is a chamber in the heart) dysfunction and sclerotic aortic valve, and mild AR can all be age-related but still place you at risk for heart failure in the long run; although not currently. So in response to your query, no sir, there is no immediate risk for a myocardial infarction (MI), but there is a risk in the future which should be moderated and reduced with the help of medication like ecosprin. If you feel that the ecosprin or aspirin is not suiting you, then you could revisit your doctor and request for replacement with drugs like warfarin. I hope you find my response both helpful and informative. Please feel free to write back to me for any further clarifications sir, I would be more than happy to help you. Best wishes.