Comprehensive screening is required to minimize the risk of heart problems while scuba diving. A table is presented to educate divers and future divers about heart problems and the sport. The table is subdivided into diagnosis, diving problem and solution.
Surveys of sudden death in sports indicate that most of these incidents are owing to narrowing of the coronary arteries. The nature of this disease is such that narrowing may occur over many years without any indication. The arteries narrow until a severe obstruction is present or the severely narrowed artery is completely blocked by formation of a blood clot and a heart attack occurs. The associated abnormality of heart rhythm can cause sudden death.
Artery narrowing is caused by the process called atherosclerosis. Narrowing in arteries (or any other blood vessels) can progress for a significant time without limiting blood flow. An artery that is only mildly narrowed (30 percent reduction of the internal diameter, for example) will not limit flow except at very high demands. When the reduction in diameter exceeds 50 percent, oxygen supplied to the heart muscle may be inadequate during exercise. If a person does not exercise to a high enough level, no symptoms will occur even though a narrowing is present. As the narrowing progresses to 70 to 80 percent loss of diameter, flow is limited even at low levels of exercise. If the severe narrowing is undetected and diving is the next strenuous exercise, the first evidence of a heart problem may appear while diving.
Atherosclerosis is accelerated by cigarette smoking, high cholesterol, hypertension, diabetes and lack of exercise – and progresses with age. The diver most prone to a heart problem, therefore, is a male over 40 years old who is a long term smoker, has hypertension, is overweight, has a high cholesterol level and does not exercise. Unfortunately, this describes a significant portion of the population and raises concern for heart risk while doing any form of exercise, including diving. Sport diving is an increasingly popular recreation and individuals in their 50s, 60s and even 70s are becoming divers. Participation of divers in these age groups means some individuals with undetected coronary disease will be diving.
To reduce the risk of heart problems while diving, careful screening is necessary. Divers in good physical condition from a continuing exercise program, who avoid risk factors by not smoking, controlling diet to reduce cholesterol and maintaining a normal blood pressure, are at low risk. If coronary artery narrowing occurs, those who exercise frequently should notice symptoms before the narrowing becomes severe. Usual manifestations include pains in the chest, neck or arms or difficulty with breathing associated with exercise. Some people only have abnormal heart rhythms associated with a narrowed artery and their first symptom may be dizziness associated with exercise. Symptoms of this type demand immediate evaluation, as the narrowing may worsen rapidly and completely close the artery. Those who develop pain associated with a narrowed artery have a signal when blood flow to the heart is inadequate, those who develop abnormal rhythms have no warning and may die suddenly.
Diving has, unfortunately, become one of the sports that brings out the initial evidence of a narrowed coronary artery. On dry land, a person who suffers a cardiac arrest has some chance of survival if trained and astute people are nearby. When diving, cardiac resuscitation is rarely successful even when the loss of consciousness is detected early. In most cases, the event is not detected and the diver drowns before any help can be provided.
Coronary disease is the most common form of heart disease, however, other forms may also cause problems with diving. Abnormalities of the heart valves, inherited abnormalities, disease of the heart and rhythm problems all raise questions about diving. Many of these disorders are already known and the patient has adjusted to the problem. Whatever the disorder of the heart, a thorough understanding of the impact of exercise and diving on the disorder must be established, both by the patient and the physician, in order to make an informed decision about diving.
The increasing incidence of sudden death among divers has prompted a more vigorous effort to detect and treat heart problems before a serious event occurs. This approach also prevents heart damage, which eventually causes the heart to fail and the person to become permanently disabled.
Atherosclerosis accounts for about 75 percent of heart problems. The best protection from the consequences of atherosclerosis is to avoid the disease. Prevention begins with reducing risk factors. These include cigarette smoking, high blood pressure, high cholesterol, lack of exercise and high stress levels. High blood pressure and high cholesterol can be modified by proper diet but, in some cases, medication may also be needed. Blood cholesterol should be below a level of about 200 and blood pressure should be 120/80. Increases in normal levels occur with age.
If cholesterol or blood pressure are above acceptable levels, they are abnormal and risk for blood vessel disease is increased. You should know what your numbers are for both of these measurements and work to keep them normal. Help from your physician is important if diet does not succeed.
The other risk factors require personal commitments to a healthy lifestyle. The best your physician can do is provide advice and moral support. The nicotine patches are helpful in some people but they won’t work without a strong commitment to give up smoking. It is sad to see people in their 60s who should be enjoying a healthy retirement but are disabled by disease of the blood vessels. Once the damage has occurred, there is no returning to the past – good health habits now are your insurance for good health in the future.
A heart evaluation begins with a thorough physical examination and a careful medical history taken by your physician. Since risk is related to the factors mentioned above, individuals below the age of 40 with no risk factors are unlikely to have coronary artery disease. A careful history is most important in being sure a younger individual has no evidence of other heart problems.
There remains a small population of young individuals who have undetected heart problems other than coronary disease. They may have an abnormality of the heart itself (cardiomyopathy). This disease can cause sudden death because of abnormal heart rhythms induced by exercise. The sudden death of several college and professional athletes has heightened awareness of this disease. Detection and prevention are difficult. Individuals suspected of the disorder should not dive. Screening is usually completed with an exercise stress test. This puts the subject under an exercise stress that equals or exceeds the stress of diving and allows careful monitoring of the electrocardiogram and blood pressure to search for abnormalities. These require evaluation and treatment to be certain diving is safe.
Diagnosis of a heart disorder does not mean diving is prohibited. Each case must be evaluated individually, based on the specific disorder, the general health of the diver and the potential for complications while diving. Many heart disorders are benign and will not complicate diving in any way. Others will cause excess risk and must be treated or the diver advised to give up diving. Many can be treated to restore the ability to dive. I generally do not advise heart treatment just for diving. Treatment for most heart disorders aims to remove disability for employment or to improve life expectancy. The same treatment may also allow a return to exercise and recreational sports, including diving.