I have received queries from 50+ years old divers asking if they can dive post heart surgery. Added queries are on how safe is to dive for divers who have heart related diseases.  There is no thumb rule to answer this question. DAN recommends waiting six months to a year after a heart attack or heart surgery before considering diving again. Then one should test their dive fitness with a stress test, where heart function is monitored while one exercises at increasing intensity on a treadmill. DAN doctors advise that they be able to exercise up to a level of 13 METs - the equivalent of running an eight-minute-mile pace for a few seconds - without adverse symptoms. That's the sign of a healthy, dive-ready heart. Individual also need to be symptom-free. If individual's have chest pain, light-headedness or breathlessness during exertion, they should not be diving. Blood-thinning heart medicines may require more conservative dives because they increase the risk of excessive bleeding in the case of ear, sinus or lung injuries.

In any case, you should be comfortable going in water. Do keep your Dive Lead and Buddy aware that you have a risk factor. If you are scared of underwater scenario, stop immediately, signal your buddy and start ascent as per procedure. Finally, always talk to your Doctor before heading into water.