A shocking way to treat a heart called cardioversion

Dear Dr. Donohue: Will you write something about cardioversion? If successful, what does it accomplish? What is the percentage of success? If it fails, is it tried a second time? Is it more successful in the young? -- N.R.

Answer: Cardioversion is a jolt of electricity delivered to an erratically beating heart by paddles placed on the chest.

At times cardioversion is an emergency treatment. I'm sure you have seen many medical programs on television where doctors cardiovert patients. Ventricular tachycardia and ventricular fibrillation are two potentially lethal heart rhythms that must be terminated quickly with cardioversion. Hearts with these rhythms are poor pumps. Without immediate action, too little blood flows to the brain and body.

A less life-threatening and more common heart rhythm for which cardioversion is often used is atrial fibrillation. Here the upper heart chambers, the atria, are not beating. They quiver.

Blood stagnates in the quivering atria, and blood clots form. Those clots can break loose from the atria and be swept to the brain where they obstruct blood flow. That is a stroke. Cardioversion's return of the heart to a normal rhythm prevents clots and strokes.

Successfully converting atrial fibrillation to a normal heartbeat rhythm depends on: 1. how long the heart has had that rhythm; 2. the patient's age -- younger people respond better than older people; 3. if there is some other heart abnormality, such as a deformed heart valve.

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