What are the sensing abnormalities and safety issues associated with implantable cardioverter defibrillator (ICD) therapy in patients with congenital short QT syndrome?
ICD treatment in patients with congenital short QT syndrome carries a high risk of inappropriate shocks due to T wave oversensing, requiring careful programming of sensitivity and decay delays.
INTRODUCTION: A congenital short QT interval constitutes a new primary electrical abnormality associated with syncope and/or sudden cardiac death. We report on the initial use of implantable cardioverter defibrillator (ICD) therapy in patients with inherited short QT interval and discuss sensing abnormalities and detection issues. METHODS AND RESULTS: In five consecutive patients from two unrelated European families who had structurally normal hearts, excessively shortened QT intervals, and a strong positive family history of sudden cardiac death, ICDs were placed for primary and secondary prevention. Mean QT intervals were 252 +/- 13 ms (QTc 287 +/- 13 ms). Despite normal sensing behavior during intraoperative and postoperative device testing, 3 of 5 patients experienced inappropriate shock therapies for T wave oversensing 30 +/- 26 days after implantation. Programming lower sensitivities and decay delays prevented further inappropriate discharges. CONCLUSION: The congenital short QT syndrome constitutes a new clinical entity with an increased risk for sudden cardiac death. Currently, ICD treatment is the only therapeutic option. In patients with short QT interval and implanted ICD, increased risk for inappropriate therapy is inherent due to the detection of short-coupled and prominent T waves. Careful testing of ICD function and adaptation of sensing levels and decay delays without sacrificing correct arrhythmia detection are essential.
Schimpf et al. (Mon,) studied this question.