Background:
Implantable cardioverter defibrillator (ICD) is currently indicated for the treatment of long QT syndrome (LQTS) patients who survived aborted cardiac arrest. However, data regarding the role of ICD in primary prevention in patients with LQTS is scarce.
Methods:
The study population comprised 212 LQTS patients (65% genotype positive) from the Rochester LQTS Registry who had ICD implantation for primary prevention. Cox regression model was used to identify clinical variables that were associated with appropriate shock and inappropriate shock. The efficacy of β-blockers was determined using a time-dependent analysis.
Results:
During a median follow up time of 9.2±4.9 years the cumulative event rates of appropriate shocks and inappropriate shocks were 23% and 34% respectively. In the entire cohort appropriate shock was associated with QTc ≥ 550 msec (HR=3.94; CI 2.08-7.46; p<0.001) and prior syncope on β-blockers (HR=1.92;(CI 1.01-3.65, p=0.047), β-blockers trended to be protective (HR=0.52; CI 0.26-1.07; p=0.075). Importantly, prior syncope was only important if it happened while on β-blockers. Inappropriate shock was significantly associated with age below 15 at implantation (HR=1.94; CI 1.11-3.38; p=0.019). In patients with positive genotype, appropriate shock was associated with QTc ≥ 550 msec (HR=5.37; CI 2.38-12.10; p<0.001), implantation age ≤ 15 years (HR=2.77; CI 1.08-7.11; p=0.034), LQT2 vs. LQT1 (HR=2.47; CI 0.93-6.52; p=0.069), and multiple mutations vs. LQT1 (HR=2.87; CI 0.88-9.42; p=0.081); β-blockers were significantly protective (HR=0.23, CI 0.09-0.59, p=0.002).
Conclusions:
Among LQTS patients in whom ICD is implanted for primary prevention, QTc duration and history of syncope while on β-blockers therapy are associated increased risk for appropriate shock. β-blocker treatment remains important in this high-risk group. Those with an ICD implanted before age 15 were at a higher risk of receiving an inappropriate shock.
Short QT syndrome and arrhythmogenic cardiac diseases in the young: the challenge of implantable cardioverter-defibrillator therapy for children
