We have heard from a number of divers who developed coronary artery disease and required bypass surgery to obtain relief from their symptoms. The question that always comes up is whether diving can be resumed after the patient has recovered from the surgery.

To answer this question properly requires a thorough knowledge of the individual diver’s case history and information obtained from the tests done before surgery and the nature of the bypass operation that was performed. A little more understanding of coronary disease and the results of surgery may help to provide some understanding.

Coronary artery disease affects the vessels that supply blood to the heart muscle. For reasons we don’t entirely understand, the inner lining of the vessels can be damaged by accumulation of fatty deposits and scar tissue can build up to the point where the artery is partially blocked. Consequently, blood cannot flow through the blockage at rates adequate to supply the needs of the beating heart muscle. The problem is much akin to rust collecting in a metal pipe until slowing of the water flow occurs. Normally the plumber would remove the section of blocked pipe and replace it with a new piece. In some cases, he might bypass the blocked pipe and disconnect the blocked segment altogether. In the case of the coronary arteries, the surgeon bypasses the blocked vessel with a piece of vein taken from the leg or occasionally with a segment of artery obtained from inside the chest. This procedure allows blood to flow from the main feeder artery of the body (called the aorta) to the heart muscle and bypass the blocked area so that the heart muscle can obtain enough blood to function normally and have adequate oxygen supply.

When a coronary artery is partially blocked by an atherosclerotic plaque, no symptoms may be noted until the block has become severe enough that inadequate oxygen is delivered to the heart muscle under increased workloads, usually caused by the stress of physical activity. Often, the first symptom of a problem of this kind is a sensation of chest tightness or pain beneath the breast bone, during exercise, which disappears when the exercise is stopped. Other kinds of stress such as excitement, anxiety or anger can bring on the same kind of discomfort when a partial blockage of the artery is present.

Coronary Artery Disease and Scuba Diving

There are several arteries that supply the heart muscle. We usually divide them into the right and left coronary arteries: The left artery has two major branches. Each of these has secondary branches and blockage of either of the secondary branches or the main arteries can occur. Thus, more than one blood vessel may be blocked. The more blood vessels that are blocked, the more likely it is that the person will experience chest discomfort when he or she does some kind of physical exercise or is under stress. If one small branch vessel is blocked, often no evidence of its presence can be sensed at all. On the other hand, if the two main branches of the left and the right are all partially blocked then the person will usually have obvious limitations with exercise. The threshold for chest pain from coronary disease varies; some people may have none at all, while others may have very severe chest tightness or pain when minimal exercise is performed.

We can test for the presence of such blood vessel abnormalities by doing an exercise stress test and recording abnormalities on the electrocardiogram. Sometimes we use other, more sophisticated tests requiring special radio isotope techniques that allow images of the heart to be obtained that demonstrate inadequate blood flow to the heart muscle.

In many cases the person with suspected coronary disease will be subjected to a cardiac catheterization procedure which involves inserting small tubes into the blood vessels. These tubes are advanced to the heart and provide the ability to take pictures of the arteries when injected with special x-ray dye. We examine these pictures of the arteries to determine which are blocked and to make decisions about treatment.

We are finding coronary disease in individuals from age 30 and beyond. Therefore, the disease can strike individuals who are currently active in sport scuba diving. It is interesting that there are a variety of factors which we think produce increased risk for development of coronary artery disease. These include cigarette smoking, obesity, hypertension, diabetes, excess emotional stress, elevated cholesterol in the blood, physical inactivity, and a history of similar disease in members of the immediate family. The disease is epidemic in proportion right now and is presently the most serious major disease in the United States and the leading cause of death among men over the age of 30.

Diving does not provide any protection from coronary artery disease and so we find a number of divers who have developed this disease, have had bypass surgery and would like to get back into diving again.

This involves careful evaluation of all the medical information available, including the results of the cardiac catheterization. It should be clear that a person who has four or five blood vessels that are partially blocked and in whom the surgeon could bypass three and had to leave several unbypassed would still be likely to have problems with delivery of oxygen to part of the heart muscle even though the surgical procedure was successful and the person returned to normal work activities and possibly even mild exercise. On the other hand, the person with one vessel blocked whose bypass operation was done to relieve chest pain, has what we would consider complete restoration of blood flow to the heart muscle and should be able to withstand the exercise needs for sport diving. It is apparent that each case needs to be reviewed carefully by a cardiologist and each person needs to be tested after surgery to be sure that he can withstand the exercise necessary for safe diving.

The first question that one must ask after bypass surgery is whether the subject is now able to perform adequate amounts of exercise with adequate blood flow to the heart muscle. This means that a stress test should be done sometime after complete recovery has occurred (8 to 12 weeks) after surgery. This test should be observed for evidence of inadequate blood flow to the heart muscle. If a diver who has had coronary bypass surgery can demonstrate that exercise can be performed to moderate levels without any evidence of inadequate blood flow to the heart muscle, then he should be able to undertake diving again in the future. Normally, I advise patients who have had this operation to return to full activity first. Return to work usually requires 10 to 12 weeks. He should then begin an exercise program to get back in good physical condition. Sometimes the incentive to regain normal physical capacity causes people who have had this operation to get in better shape than they have been at any time of their lives, to stop smoking and avoid some of the other risk factors we know can aggravate the disease. After five or six months of a good conditioning program, it is then time to retest the subject to determine whether his capacity is improved enough to be able to return to diving. If at that time the exercise stress test shows the person can withstand a level of exercise that is about 12 to 13 times higher than rest in terms of oxygen use, then he should be able to return to sport diving with some care in avoiding adverse conditions such as extremely cold water or very deep diving.

At the present time there appears to be no problem with the surgery itself aggravating decompression sickness of difficulty with pneumothorax.

I would not recommend that a commercial diver who had coronary bypass surgery return to his occupation. Regulations in commercial and military diving would prevent the diver from returning to diving with coronary disease, with or without bypass surgery. However, with the sport diver having more control of his environment and with careful assessment of the type of diving being planned, it is possible to return to a sport diving program as long as moderation is used.

If you have had coronary bypass surgery and would like to return to diving, I would suggest that you talk to your cardiologist or cardiac surgeon and obtain a program for getting back in physical condition. Then determine how your performance is on an exercise stress test after five or six months of a physical training program. If everything is normal at that point and your stress test is negative, then it is possible to return to diving with careful consideration for the diving activities you undertake.

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