P atio of Late to Early T-Wave Peak mplitude in 24h Electrocardiographic ecordings as Indicator of Symptom History in atients With Long-QT Syndrome Types 1 and 2

OBJECTIVES We tested the hypothesis that in long-QT syndrome types 1 (LQT1) and 2 (LQT2), the diurnal maximal ratio between late and early T-wave peak amplitudes correlates with a history of symptoms better than QT interval durations. BACKGROUND Genotype and phenotype studies have delineated clinical profiles of the most prevalent LQT1 and LQT2 subtypes of inherited LQT, but prediction of arrhythmia risk remains uncertain, the baseline QTc interval being the best predictor. In experimental long-QT syndrome models, the ratio between late and early T-wave peak amplitude predicts onset of torsade de pointes. METHODS We reviewed 24-h electrocardiographic recordings from 214 genotyped subjects—97 with LQT1, 62 with LQT2, and 55 unaffected—to record maximal amplitude ratios between late and early T-wave peaks by use of a computer-assisted program. RESULTS Maximal amplitude ratios between late and early T-wave peaks were higher in symptomatic than in asymptomatic patients both in LQT1 (3.2 1.0 vs. 2.3 0.8; p 0.001) and LQT2 patients (2.6 1.0 vs. 1.7 0.5; p 0.001). Although the QTc interval also was longer in symptomatic patients, only the maximal amplitude ratio between late and early T-wave peaks was independently associated with symptoms in both LQT1 and LQT2 patients. CONCLUSIONS Maximal diurnal ratio between late and early T-wave peak amplitude improves noninvasive risk assessment both in LQT1 and LQT2 syndromes. We propose this new indicator in clinical evaluation of arrhythmia risk in LQT1 and LQT2. (J Am Coll Cardiol 2006;47: ublished by Elsevier Inc. doi:10.1016/j.jacc.2005.07.068