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An international survey identified 40 patients less than 20 years old who underwent surgical implantation of an automatic implantable cardioverter-defibrillator (AICD). There was a history of aborted sudden cardiac death or sustained ventricular tachycardia in 92.5% of these patients. Twenty-two patients (55%) had structural heart disease; dilated and hypertrophic cardiomyopathy were the most common diagnoses. Eighteen patients (45%) had primary electrical abnormalities including seven with the congenital long QT syndrome. There were no perioperative deaths associated with device implantation. Concomitant drug therapy was administered to 75% of the patients. Defibrillator discharge occurred in 70% of the patients, with 17 patients (42.5%) receiving at least one appropriate shock. There were two sudden and two nonsudden deaths at 28.2 months' median follow-up. Sudden death-free survival rates by life table analysis at 12 and 33 months were 0.94 and 0.88, respectively. Total survival rates at 12 and 33 months were 0.94 and 0.82, respectively. The AICD represents an effective treatment approach for young patients with life-threatening ventricular tachyarrhythmias.

No single electrogram characteristic had a positive predictive value and a sensitivity greater than 90% for AP localization adequate for radiofrequency current ablation. For antegrade APs, the best correlate of adequate localization was a local AV interval less than or equal to 40 msec; as a corollary, radiofrequency current applications at sites where the local AV was greater than 60 msec, were unlikely to be effective. Objective criteria for the localization of concealed APs were less certain. Electrogram analysis, as a guide to AP localization and ablation, requires careful analysis of multiple variables, with analysis of the local AV interval a salient objective factor.

During implantation of a two-lead transvenous defibrillation system, positioning the proximal defibrillation electrode in the subclavian-innominate vein will lower defibrillation energy requirements in the majority of patients.

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