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Abstract & Commentary
Synopsis: ICD therapy is an effective management strategy in selected pediatric and congenital heart disease patients.
Source: Alexander ME, et al. J Cardiovasc Electrophysiol. 2004;15:72-76.
In this paper, Alexander and colleagues present a retrospective analysis of implantable cardioverter defibrillator (ICD) therapy from a single center, Children’s Hospital in Boston. All patients younger than 30 at implant were identified at Children’s Hospital for the present analysis. The study group included 76 patients. The primary diagnosis was congenital heart disease in 32 patients, primary electrical disease in 25 patients, dilated cardiomyopathy in 6 patients, and hypertrophic cardiomyopathy in 13 patients. The mean age at the time of the initial ICD procedure was 16 ± 6 years. Only 3 patients were younger than 5, and only 6 patients were younger than 10. Eighteen patients were between the ages of 11 and 15, and 19 patients were between the ages of 16 and 20. Among the patients with congenital heart disease, 19 of 32 had tetralogy of Fallot, 5 had D-transposition of the great arteries, and 4 had aortic valve disease with left ventricular outflow tract obstruction. ICD therapy was used most frequently for secondary prevention. Sixty-one of 76 patients (80%) had a history of either cardiac arrest, syncope, or spontaneous sustained monomorphic ventricular tachycardia. Only 6 patients had no symptoms due to arrhythmia or advanced heart failure. In the 76 patients, there were 90 implants of new leads or generators. The majority (93%) of these procedures used transvenous techniques. Dual-chamber devices were used in 29 (32%) of the implants. Placement of a subcutaneous electrode array was necessary to lower defibrillation thresholds in 7 patients.
In the entire group, there was a median follow-up of 1.4 years. Overall survival was 95%. Six patients underwent cardiac transplantation. During follow-up, 28% of the patients experienced at least a single episode of appropriate therapy—shock or antitachycardia pacing. The median time to first shock was 13 months. Inappropriate therapy was observed in 25% of the patients. The reasons for inappropriate therapy were: lead failure (7 patients), sinus tachycardia (8 patients), supraventricular tachycardia (4 patients), and T-wave oversensing (2 patients). Patients with inappropriate therapy experienced a mean of 7 ± 15 inappropriate discharges. The patients with lead failure received the greatest number of inappropriate shocks.
Other problems were also frequently noted. There were 11 patients (14%) who developed acute complications that extended hospital stay or required a repeat procedure. These included 2 pocket infections, 2 pocket hematomas, and single episodes of hemothorax, superior vena cava syndrome, pneumonia, electromechanical dissociation during fibrillation testing, second degree burns from external rescue shocks, and one acute lead dislodgement. In addition, there were 38 chronic complications noted in 29 patients. The most frequent chronic complication was lead failure, which was seen in 21% of the patients. Patients who were the youngest and the smallest at the time of implant and those who had the greatest growth after implant had the highest rate of lead complications.
Alexander et al conclude that ICD therapy is an effective management strategy in selected pediatric and congenital heart disease patients. Defibrillator shocks and lead failure are important problems in this population.
Comment by John DiMarco, MD, PhD
ICD therapy is now a well-established option for managing life-threatening ventricular arrhythmias in adult patients with coronary artery disease and most other forms of acquired heart disease. However, there are additional factors that must be made before recommending an ICD in a child or teenager. This paper by Alexander et al reports a single-center experience with ICD therapy in children. However, the group is mixed, with 42% having congenital heart disease, 5% having some form of cardiomyopathy, and 33% having primary electrical disease. These 3 groups present somewhat different problems.
In patients with congenital heart disease, life-threatening ventricular arrhythmias often occur in association with scars related to curative surgery or as a result of ventricular dysfunction in patients who are inoperable or who have an incomplete hemodynamic response to surgery.
Patients with scar-related ventricular tachycardia are very similar to those with ischemic heart disease and are well managed with an ICD if curative ablation is not possible.
Patients with failure after surgery from congenital heart disease may present with a complex cardiac anatomy, and standard transvenous approaches for ICD placement may be difficult or even impossible. In addition, the defibrillation pathway in an ICD was designed with the left ventricle as the target. Since many patients with complex congenital heart disease have predominantly right ventricular involvement and enlargement, defibrillation may be more difficult. It is now almost unheard of to not have a satisfactory defibrillation threshold in an adult with coronary disease, but this study reports a relatively frequent need for subcutaneous arrays to lower defibrillation thresholds. Among patients with cardiomyopathy, there is also a difference between those with dilated cardiomyopathy and hypertrophic cardiomyopathy. The prognosis in the former group is usually determined by hemodynamic status. Many young patients with hypertrophic cardiomyopathy, however, may be relatively asymptomatic but still be at risk for arrhythmias and sudden death. In patients with hypertrophic cardiomyopathy and in primary electrical disease, implantation in young active individuals is problematic since they are often very active. This can lead to a relatively high incidence of lead failure as is reported in this series, which covered only a short follow-up period. In patients with primary electrical disease and hypertrophic cardiomyopathy, one would expect patients to require ICD therapy for decades. As a result, these patients are likely to require multiple device procedures, and care must be used to try to preserve venous access and subcutaneous sites for device implants. When the ICD is to be placed for primary prevention, it is hard to know at what age to intervene. I prefer to wait until age 12 or so, if at all possible. When a decision to implant is made, doing the minimum necessary to provide sudden death protection rather than going for more complex initial procedures is often the best approach.
Dr. DiMarco, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville, is on the Editorial Board of Clinical Cardiology Alert.