The rhythm can go wrong in many different ways, but the real killer is ventricular tachycardia. Ventricular tachycardia is an abnormal heart rhythm that starts in the ventricles rather than from the sinoatrial node, and that causes the heart to beat at a rate too fast (tachy is Greek for rapid or fast) to efficiently pump blood to the rest of the body.
Moreover, the rapid heartbeat can degenerate precipitously into ventricular fibrillation, or the loss of all rhythm, says Efimov. During ventricular fibrillation the uncoordinated contraction of heart muscle prevents the heart from pumping blood at all, and without immediate intervention, death quickly follows.
Most people who develop ventricular tachycardia and ventricular fibrillation outside the hospital die, says Janardhan, but studies show that if we implant a defibrillator in patients with a weak heart that does not pump as strongly as it should, we can significantly reduce mortality.
Restarting the rhythm
There are really only three therapies for ventricular tachycardia, Efimov says. One is drugs that reduce the likelihood of tachycardia, but drugs are often ineffective.
The second is ablation, or the deliberate creation of nonconductive scar tissue within the heart that blocks abnormal conductive patterns and redirects electrical activity to more normal pathways.
The major problem with ablation, says Efimov, is recurrence. It's a temporary measure, not a cure. Patients typically need additional treatment within five years.
The third therapy is an implantable cardioverter defibrillator, or ICD. These devices are placed beneath the skin in the chest and monitor the rate and rhythm of the heart. If they detect ventricular tachycardia, they try to break the rhythm by pacing the heart at a rate faster than its intrinsic rate, a strategy anti-tachycardia pacing.
|Contact: Diana Lutz|
Washington University in St. Louis