3 Months Ago I Had 5 Bypasses Surgery Did Not

3 months ago I had 5 bypasses surgery did not suffer an heart attack before surgery they did an echocardiogram i was at 50 % today I had an post echocardiography done dr said results are now at 35% don't understand I haven't felt this good I'm up to jogging an mile an day could the echocardiogram be wrong I'm suppose to take an nuclear stress test in an few days