IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR USE IN PEDIATRIC PATIENTS

IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR USE IN PEDIATRIC PATIENTS "clearly represents an effective form of therapy for recurrent ventricular tachyarrhythmias in young survivors of sudden cardiac death," Michael Silka, MD, Oregon Health Sciences University, Portland, et al. conclude in a study published in the March issue of the American Heart Association journal Circulation. The authors determined that pediatric use of ICDs "appears valid" after a retrospective study of patients ranging in age from two to 20. Under the auspices of the Pediatric Electrophysiology Society, the research team gathered data on 125 international patients (65 female and 112 male) who received ICDs between October 1980 and October 1991. Mean age of the patients at the time of implant was 15, and mean weight was 45 kilograms. Patients received ICDs manufactured by Medtronic, Ventritex, Telectronics or Cardiac Pacemakers, Inc. currently available on a commercial or investigational basis. In 95 of the 125 patients (76%), the indication for initial ICD implantation was aborted sudden cardiac death (SCD). The study defined SCD as "death occurring within one hour of onset of symptoms in a previously stable patient, an unwitnessed death or death during sleep." Other indications included drug refractory ventricular tachycardia and "unexplained syncope" with structural heart disease. Using actuarial data, the estimated overall post-ICD implant survival rates at one, two and five years were 95%, 93% and 85%, respectively. Over a mean followup period of approximately 31 months, at least one ICD discharge occurred in 85 (68%) of the patients. Seventy-three patients (59%) received at least one "appropriate" ICD discharge, while 25 patients (20%) had one or more "spurious or indeterminate" discharges. An appropriate discharge was defined as an ICD shock "delivered in response to a ventricular arrhythmia." There were a total of nine deaths during the course of the study period: five due to SCD, two due to recurrent ventricular arrhythmias, and two related to congestive heart failures. According to the survey, "abnormal ventricular function was the only significant correlate of death." There were no deaths among the 55 patients reported to have normal ventricular function; all deaths occurred in patients with impaired functioning. The study also notes that similar data "implicating the role of ventricular function as the primary determinant of long-term survival are established for adult ICD recipients." Silka et al. point out that "patterns of ICD discharge observed in young patients, and thus, inferred risk of recurrent life threatening arrhythmias, are similar to those of adult survivors of SCD." The study concludes, therefore, that the same implant selection criteria used for adults could be used in pediatric patients. However, the researchers note the "uncertainties" and "multiple methodological" limitations of the study. In a press release, Silka states that prospective studies with extensive followup are needed to assess the long-term prognosis for young survivors of SCD before ICD treatment becomes "definitive."