I agree with Ed. If you have any signs of respiratory stress (trouble breathing, hard breathing while wearing scuba gear) it may be prudent to have an excercising stress test to see if you can push 14 METS with out any abnormality on a EKG.
New England diving is much different than the tropics; we are loaded with weight, have thick tight wetsuits, have coldish water, low vis etc. We also tend to overheat gearing up in the heat putting even more stress on our heart and lungs. It can be tough diving and puts stress on the cardio-vascular system.
Even a healthy diver can have respiratory arrest from gearing up in the heat and a walk to the dive site. All it takes is a high demand on the heart and lungs such that the heart goes into a type of fibulation that can't be reversed without quick medical intervention.
I remember diving Folley Cove with ScubaBills on a 95 F day. I had water pouring out of my face and froze 20 mins into the dive in 50 F water. Thank you to that unknown diver who helped me into the water.
I also remember exiting the left cove at Ft Wetherall in a 3 ft snow bank and having my tank slip out of the tank strap. I had to remove my gear with frozen hands. Talk about the stress I endured.
A stress test is a prudent thing to have for us older divers along with a healthy diet and moderate excercise and avoiding dehydration.
My heart goes out the the diver and those close to him. Time for another memorial bench at Folley Cove.