Hi thanks for asking question. Your stress test normal that is suggesting good functioning of cariorespiratory work. If you still want to do further work up then echo cardiography or ECG can be done. Do you have hypertension? If it present chances of heart failure more. If heart failure present then you might have fluid collection means edema somewhere if it is progressive. Meanwhile continue with healthy lifestyle -low salt -avoid stress -low cholesterol -green leafy veg more Let me know you that any organic damage can t reverse back.If you had previous damage by any reason like heart attack or other then damage that already occurred replaced by scar .But it can t reverse. With healthy life style normal life can be lived. Don t worry Continue with good dietary habit and regular exercise. Wish you good health