Patients who have had successful coronary bypass surgery or angioplasty who wish to undertake sport diving should be allowed to participate in this activity.
Those applicants wanting to do commercial or military diving should not be approved.
In arriving at the proper conclusion a careful review of coronary anatomy, degree of vascularization, and exercise tolerance (exercise test) should be undertaken. If the person can exercise with no ischemia (decreased blood supply, or angina (chest pain), normal blood pressure response, and no serious heart irregularity (arrhythmia), limited sport diving may be considered. Limited sport diving involves warm water, shallow depths, minimal currents with ease of entry and exits.
Limitation of Response to Exercise
Artificial (prosthetic) cardiac valves create two important problems in divers and potential divers. In high output states related to exercise, there may be a significant gradient (pressure and turbulence) across the valve, and with high heart rates, the valve poppet may not open and close completely, thus aggravating the gradient or producing significant valve regurgitation (leakage).
Because of these limitations, patients who have prosthetic cardiac valves should not dive. However, individual exceptions for carefully constrained sport diving can be made. The use of center opening valves, including heterograft valves with tissue leaflets that open with larger orifices and have less mass, provides the possibility for greater cardiac output and, therefore, greater exercise capacity.
Dangers of Anticoagulants
The second consideration in divers with prosthetic cardiac valves is anticoagulation. Because diving often results in barotrauma and minor trauma, anticoagulation is likely to produce excess bleeding in situations that produce blunt trauma, injury, or bruising. Heterograft valves provide a significant advantage in this regard since patients with heterograft aortic valves can be followed without anticoagulation after an initial period for recovery from surgery. Patients with heterograft mitral valves often are maintained on anticoagulation.
Divers and diving candidates with prosthetic heart valves must also be evaluated for cardiac function. Often chronic valvular disease results in decreased ventricular function and a state of chronic heart failure, which will compromise exercise performance when diving. To resolve questions about exercise capacity with prosthetic valve patients, an exercise test is a good screening tool.