DAN Medical Frequently Asked Questions
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Overview of Arrhythmias
>The term "arrhythmia" (or, sometimes, "dysrhythmia") means an abnormal heartbeat. It is used to describe manifestations ranging from benign, harmless conditions to severe, life-threatening disturbances of the heart's rhythm.
ad:media]A normal heart beats between 60 and 100 times a minute. In well-trained athletes, or even select nonathletic individuals, the heart may beat at rest as slowly as 40 to 50 times a minute. Even entirely healthy, normal individuals experience occasional extra beats or minor changes in their heart's rhythm. These can be caused by drugs (such as caffeine) or stress or can occur for no apparent reason. Arrhythmias become serious only when they are prolonged or when they do not result in proper contraction of the heart.
>Physiologically significant extra heartbeats may originate in the upper chambers of the heart (this is called "supraventricular tachycardia") or in the lower chambers of the heart (this is called "ventricular tachycardia"). The cause of these extra beats may be a short circuit or an extra conduction pathway in the heart's wiring, or it may be the result of some other cardiac disorder. People who have episodes or periods of rapid heartbeat are at risk of losing consciousness during such events. Other people have a fairly stable arrhythmia (such as "fixed atrial fibrillation") but in conjunction with additional cardiovascular disorders or other health problems that exacerbate the effect of their rhythm disturbance. A too-slow heartbeat (or a heart blockage) may cause symptoms, too.Serious arrhythmias, such as ventricular tachycardia and many types of atrial arrhythmia, are incompatible with diving. The risk for any person who develops an arrhythmia during a dive is, of course, losing consciousness while underwater. Supraventricular tachycardia, for example, is unpredictable in its onset and may even be triggered simply by immersing one's face in cold water. Anyone who has had more than one episode of this type of arrhythmia should not dive.
>Most arrhythmias that require medication also disqualify the affected individual from safe diving. Exceptions may be made on a case-by-case basis in consultation with a cardiologist and a diving medical officer.
>An individual who has any cardiac arrhythmia needs a complete medical evaluation by a cardiologist prior to engaging in diving. In some cases, electrophysiologic studies can identify an abnormal conduction pathway, and the problem can be corrected. Recently, clinicians and researchers have determined that people with some arrhythmias (such as certain types of Wolff-Parkinson-White syndrome, which is characterized by an extra electrical pathyway) may safely participate in diving after a thorough evaluation by a cardiologist. Also, in select cases, people with stable atrial arrhythmias (such as uncomplicated atrial fibrillation) may dive safely if a cardiologist determines that they have no other significant health problems.