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I am frequently asked about diving by those with blockage of an artery. The most recent inquiry was from a 48 year old man who had complete blockage of one of his carotid arteries (the arteries that supply the brain) and a 50 percent narrowing of the other. These two arteries are on opposite sides of the neck and blockage of either can cause a stroke. The man had not experienced a stroke but wondered if he should continue sport diving. There was no other evidence of blood vessel disease but he was overweight, smoked two packs of cigarettes daily and had high blood pressure. My advice was to give up diving until he could reduce his risk of a catastrophic event related to occlusion of an artery.
The problem with the diver mentioned above is that disease of blood vessels usually involves all of the body’s arteries. Atherosclerosis causes injury to their inner lining. Blood clots, fatty material and calcium form deposits in and on the inner lining, causing a progressive narrowing of the artery until it finally occludes completely. A totally occluded artery deprives the organ or tissue it supplies of oxygen and nutrients carried by the blood. Tissue injury, damage and abnormal function are usually the consequences. The organs that suffer the most severe complications when atherosclerosis blocks an artery are the brain, heart and the kidneys. Blocked arteries to the intestines can cause severe problems with digestion and sometimes death of parts of the bowel, which is often fatal. Another common problem is blockage of an artery to the leg, which causes severe pain when walking or swimming.
When atherosclerosis is present in one artery, we make a strong effort to find disease in other arteries. For example, when there is disease in the arteries to the legs, we search for disease in the arteries to the heart and brain. Although pain and cramps in the legs are a serious problem, heart attack and stroke are worse. These are best managed by prevention, not therapy after an event has occurred. My concern with diseased carotid arteries is the risk for stroke as well as heart attack because of the known association of disease in the arteries to these two important organs.
Prevention: Atherosclerosis is often preventable by simple measures. The factors associated with high risk are cigarette smoking, high cholesterol, high blood pressure, diabetes, age and a history of premature atherosclerosis in relatives. Only two risk factors cannot be changed: family history and age. All the others are easily modified by changes in lifestyle, diet and medication.
Lifestyle: Stress, smoking, lack of exercise and cocaine all contribute to atherosclerosis. Tobacco and cocaine cause direct injury to arteries. Avoiding these risk factors is a commitment to a healthy lifestyle.
Diet: A balanced diet of the proper number of calories contributes to lowering the risk of blood vessel disease in three ways. First, a proper diet should maintain the blood lipids (cholesterol, triglycerides) at a normal level. There is ample evidence that abnormal blood cholesterol and its components (elevated low density lipoprotein-LDL, reduced high density lipoproteins-HDL) contribute to atherosclerosis. Avoiding foods high in saturated fats and cholesterol will accomplish these goals.
Your diet should contain enough calories to maintain weight but not to gain or lose. If you are overweight, your diet should be reduced to allow reduction to ideal body weight. Increased weight is associated with abnormal blood lipids, high blood pressure and diabetes. Third, as noted, diabetes will occur in many people when they become overweight. When the weight is lost, they return to normal. Diabetes also increases the risk for atherosclerosis-in fact, many experts feel atherosclerosis is actually part of diabetes.
Medications: Substantial gains in the prevention of atherosclerosis have been made in the past 20 years. Studies show that lowering blood cholesterol with medication reduces the risk of atherosclerosis and may even reverse some of the damage that has already occurred. Lowering blood pressure with medication is readily accomplished and has been shown to reduce the risk for stroke, heart attack and kidney failure. In many adults who develop diabetes later in life, oral medication is highly successful in reversing its effects. If you are a diver and need any of these medications to maintain good health, you can still dive, as most of the medications used for control of blood pressure, blood cholesterol and diabetes do not cause problems with diving if taken in moderate amounts.
With the knowledge now available on how to prevent disease of blood vessels, and the many medications available to bring blood pressure, cholesterol and blood sugar under control, catastrophic strokes or heart attacks while diving should be almost zero. You can find more on diving medicine at our Web site, www.scubamed.com.