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Health & Diving
The Heart & Diving

The Heart & Diving

Sudden Cardiac Arrest

Sudden cardiac arrest (SCA) — a cessation of the heart's beating action, with little or no warning — is an acute medical emergency. During the arrest, blood stops circulating to the body's vital organs, including the brain, the kidneys and the heart itself. Cut off from oxygen, these organs die within minutes. If the arrest is not corrected quickly, the affected individual will not survive.

The causes of SCA include myocardial infarction (heart attack), heart failure, drowning, coronary artery disease, electrolyte abnormalities, drugs, abnormalities in the heart's electrical conduction system, cardiomyopathy (a weakening of the heart muscle) and embolism (a clot that has lodged in a major vessel).


SCA accounts for 450,000 deaths in the United States each year and for 63 percent of cardiac deaths in Americans more than 35 years old. The risk of sudden cardiac death in adults increases as much as sixfold with increasing age, paralleling the rising incidence of ischemic heart disease. The risk of SCA is greater in those with structural heart diseases, but in 50 percent of sudden cardiac deaths the victim had no awareness of having heart disease, and in 20 percent of autopsies conducted following such deaths, no structural cardiovascular abnormalities were found.

Though there is typically little warning before a sudden cardiac arrest, occasionally the individual may experience lightheadedness, difficulty breathing, palpitations or chest pain.

Immediate treatment should be focused on restoring circulation quickly using chest compressions or CPR and defibrillation. Following resuscitation, the victim should be transported to a hospital as soon as possible. Subsequent treatment may consist of efforts to eliminate the underlying cause of the arrest through administration of medication, surgery or the use of implanted electrical devices.

Preventive strategies include learning to recognize the warning signs of SCA, in case they occur; identifying, eliminating or controlling any risk factors that may affect you; and scheduling regular physical exams, as well as appropriate testing, when it is indicated.

Effect on Diving

Divers with any symptoms of cardiovascular disease should be evaluated by a cardiologist and a dive-medicine specialist regarding their continued participation in diving. In asymptomatic individuals, the risk of SCA may be evaluated by using known cardiovascular risk factors such as smoking, high blood pressure, high cholesterol, diabetes, lack of exercise and overweight. For example, people who smoke have two and a half times the risk of suffering sudden cardiac death than do nonsmokers.
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