CHICAGO — Adults with congenital heart disease face an increased risk of ventricular arrhythmias and sudden cardiac death, but that doesn't mean they should all get an implantable cardioverter defibrillator.
“We must be very careful using ICDs [implantable cardioverter defibrillators] for primary prevention” of ventricular arrhythmias in adults with congenital heart disease, Dr. Sing-Chien Yap said at the annual scientific sessions of the American Heart Association. That's despite the fact that in these patients the risk of sudden cardiac death is 25–100 times greater than in the general population.
The major limitation on using ICDs in these patients is their rate of inappropriate shocks, which are primarily triggered by supraventricular arrhythmias in adults with congenital heart disease. In a series of 64 Dutch adults with congenital heart disease who had an ICD, the incidence of inappropriate shocks was 41% during 3.7 years of follow-up, an annual rate of about 11%, said Dr. Yap, a cardiologist at the Thoraxcenter of Erasmus University in Rotterdam, the Netherlands. This is a “very high number,” Dr. Yap said. In more typical patients with ICDs, the annual rate of inappropriate shocks is less than 5%.
“Inappropriate shocks are the dark side of ICD therapy,” said Dr. Yap. The problem is the relatively high rate of supraventricular arrhythmias in adults with congenital heart disease. In the 64 patients that he reviewed, about 30% had a history of atrial arrhythmias. “We're becoming more and more conservative when implanting ICDs” in these patients.
A different perspective on the role of ICDs in adults with congenital heart disease was offered by cardiologists at Ohio State University and Columbus Children's Hospital, both in Columbus. Since January 2005, they have managed 41 adults with congenital heart disease who met their criteria for undergoing a surveillance electrophysiology study. An inducible ventricular arrhythmia was found in 17 patients (41%), of whom 15 had an arrhythmia that was immediately inducible without need for treatment with isoproterenol. Ten of these patients received an ICD, said Dr. Shane F. Tsai, a cardiologist at Ohio State. So far during intermediate-term follow-up, none of the ICDs has delivered a shock.
“We're not recommending ICDs for all of these patients, but it's been our choice to be very aggressive,” Dr. Tsai said. It's not yet clear which adults with congenital heart disease need surveillance by electrophysiology studies and what benefit they might gain from an ICD, he cautioned. “The real issue is do we reduce deaths,” but proving that will require longer follow-up, he said.
In the Dutch study, the cumulative rate of appropriate shocks during 3.7 years of follow-up was 23%, about 6% per year, which means the usefulness of ICDs in these patients is roughly comparable to the 7% annual rate that was reported for patients with hypertrophic cardiomyopathy, Dr. Yap said.
An analysis of the 64 patients who got ICDs failed to identify any feature that helped to predict an increased or decreased risk of receiving inappropriate shocks. The only feature able to identify patients with a significantly reduced risk of receiving appropriate shocks was having tetralogy of Fallot as the congenital disease.
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