The
Cardiomyopathy
Association

New data has shown that nearly half of patients who have internal defibrillators (ICDs) fitted because they are thought to be at risk from dangerous heart rhythms have an appropriate treatment from their devices.

The study looked at 84 patients with definite or probable arrhythomogenic right ventricular cardiomyopathy (ARVC). None had a history of life-threatening irregular heartbeats, called sustained ventricular arrhythmias, but all had been given an implanted defibrillator as a precaution and were followed for an average of five years.

During that time, 48 percent needed either a shock or rapid pacing from the device to stop a dangerous abnormal rhythm while the remaining 52 percent did not experience an arrhythmia that required therapy from the defibrillator.

"Whether an ARVC patient should have an implantable defibrillator for primary prevention against sudden death is a critically important decision," said Dr Hugh Calkins, professor and head of cardiac electrophysiology at the Johns Hopkins ARVC programme.

“These are usually young patients with few or no symptoms, and putting in a defibrillator, which they will have for the rest of their lives, requires careful consideration," said Dr Calkins, senior author of the study.

Dr Calkins and his team identified four criteria to help determine which patients were most in need of a defibrillator. Patients whose devices produced shocks or rapid pacing to stop abnormal rhythms generally met two or more of the criteria thought to put them at higher risk.

They found that there was an incremental and additive risk to these patients the more criteria they met. So if a patient was found to match only one of the four criteria, that person was at lower risk. A patient who was positive on all four criteria was at highest risk.

One of those criteria was whether a sustained irregular heart rhythm could be induced by a procedure in the electrophysiology lab.

Two of the other criteria related to findings on a Holter monitor that patients wear for 24 hours to monitor their hearts’ electrical activity. The fourth characteristic that was found to have a higher value in predicting risk was whether the patient was the first in the family to be diagnosed with ARVC.

Researchers said their goal was to provide a good template for physicians to assess a patient's risk.  The study represented an important step in understanding the factors that predict which patients are at highest risk of sudden death and the need for an implanted defibrillator.

Details of the study were published in the Journal of the American College of Cardiology.

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