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  • 2000-08 Coronary Angioplasty, Stents and Diving
    Fred Bove, M.D. Ph.D.
    We have received a number of queries about diving after having a balloon angioplasty with stents implanted in the coronary arteries. These questions arise because of the large number of people who develop coronary disease and the newer methods of correcting the problem, often without the need for heart surgery. The coronary arteries supply blood to the heart muscle and allow the heart to beat continuously without getting fatigued. Because it must beat continuously to support life, the heart has adapted to avoid muscle fatigue.



    Coronary Disease

    Coronary disease caused by blockage of the coronary arteries, affects about 700,000 people annually, and about 250,000 die of the disease suddenly and often without warning. The disease that causes the coronary artery blockage is called coronary atherosclerosis. For unknown reasons, the process of atherosclerosis attacks the coronary arteries of the heart more frequently than other arteries of the body. Atherosclerosis can start early in life with the progressive buildup of cholesterol and other fats in the blood vessel wall, which causes a plaque to form within the artery wall. As it grows, the plaque narrows the artery and limits blood flow to the heart muscle, causing angina or chest pain during activity. This plaque becomes unstable and eventually ruptures. When a plaque ruptures, the artery narrows further. If the artery totally occludes, a heart attack usually occurs. This process is considered to be one of the major causes of sudden death while diving.



    Risk Factors

    Age, lifestyle and inheritance can affect the risk for coronary artery disease. Cigarette smoking, diabetes, high blood pressure and elevated blood cholesterol all increase the risk for coronary disease. By paying attention to your risk factors, you can reduce your chances of getting coronary disease and blockage of a coronary artery. Prevention is the best way to avoid questions about diving after angioplasty and stent implantation.



    Treatment

    Because the diving population is getting older (we started teaching sport diving in the 1950s), and the incidence of coronary disease increases with age, it is inevitable that divers will be asking about returning to diving after having an angioplasty or a stent. If prevention fails, there are several ways to correct a partially blocked artery. They include medication, coronary bypass surgery, balloon angioplastyówith or without implantation of a stentócutting devices that remove the plaque (atherectomy), and on occasion, the vaporizing of a plaque using laser energy delivered through a catheter.



    Balloon Angioplasty and Stents

    Physicians realized in the 1960s that blockages in the coronary arteries could be opened using a long tube (a catheter) threaded into the artery to push the plaque out of the way and allow more blood to flow through the artery. Then a small balloon mounted on the end of a catheter is positioned in the narrowing and inflated to push the plaque out of the way and open the artery.

    From these early beginnings, an entire field of medicine has evolved with new devices, improved skills and training, and the ability to open a blocked artery without chest surgery. Rapid advances in technology have made the procedure less complicated, improved the outcome of the procedure and improved the one year success rate.

    Improvement in the immediate and long term outcomes came from the addition of a device called a stent. A stent is a fine wire mesh tube (2-3 millimeters in diameter, 1-2 centimeters in length) that is placed in the artery with a catheter and expanded in the narrowed area of the coronary artery after opening the narrowed area with balloon angioplasty. The stent holds the artery open and is eventually overgrown with tissue so that it becomes a permanent implant in the coronary artery.

    People with blockages in the arteries that are amenable to treatment with angioplasty and a stent require short hospital stays and can return to their usual activity in a few days. We usually advise patients who have received an angioplasty and a stent to refrain from extreme exercise for about four weeks to be sure the site of insertion of the catheter (usually an artery in the groin) is well-healed and not likely to bleed from excess activity.



    Diving After Coronary Stent Implantation

    If you are a diver who has developed coronary disease and has undergone angioplasty with or without a stent, important questions are: Can I return to diving, under what circumstances and when?

    Stresses from diving include exercise and cold exposure. We usually provide recommendations for exercise based on a stress test done six to eight weeks after the procedure. Based on the stress test, we can determine if the stent is open and whether other coronary arteries are supplying adequate blood flow. We also determine your level of physical fitness and provide advice about exercise programs to improve conditioning. Because there is a risk of renarrowing in the stent, and most renarrowing occurs within the first six months after the procedure, I usually advise divers to wait for six months, get in good physical condition through a supervised exercise program, then have an exercise stress test to be sure the heart is getting adequate blood flow. For safe diving I recommend an exercise capacity of about 13 mets (a measure of work load) or 12 minutes on a standard stress test. It is also wise to avoid extremes of cold and heavy work on the surface or underwater. Smoking cessation and treatment of high blood pressure, diabetes and elevated blood cholesterol will lower the risk of a subsequent blockage. If you participate in any recreation that requires exercise, including diving after angioplasty and stent implantation, you should have periodic stress tests (annual or biannual) to be sure exercise is safe.

    More on diving medicine can be found at www.scubamed.com.