188: Prevalence of early repolarization in congenital long QT syndrome A combination of early and delayed repolarization

Abstract

early repolarization (ER) in Brugada or short QT syndrome is common and has been associated to a less favourable outcome. Even if apparently paradoxical, ER can also be seen in long QT (LQT) but prevalence and correlations to other variables are unknown. 12 lead ECG of 37 LQT pts (19 men, 39±21 yo) and 80 matched controls were reviewed. LQT pts were selected by a positive genetic testing (n=27) or by showing abnormal T wave and long QT interval (n=10) either spontaneously or during epinephrin infusion. ER was defined by >1 mm J point elevation in the inferior or lateral leads with notch or slurring pattern. Presence of ER was correlated to the clinical and ECG characteristics and results genetic analysis. QT was 409±53 msec in pts and 372±24 in controls (p<0.0001) (QTc 476±52 vs 392±26 msec, p<0.0001). Two LQT pts presented with resuscitated sudden death and 4 with syncope at the time of diagnosis. 14/37 LQT pts (38%) had ER compared to 17/80 (21%) controls (p=0.05). ER was more frequent in men (12/19, 63%) compared to women (2/18, 11%) (p=0.001) but was not correlated to age. Pts with ER had slower heart rate (63±10 vs 75±18 bpm, p=0.02). ER was not correlated to symptoms or cardiac events (no ER in the 2 pts with SD and in 2/4 pts with syncope). QT were longer in pts with ER (450±68 vs 397±54 msec in V2, p=0.01) but there was no correlations between ER and corrected QT intervals. ER was more often seen in pts with or without mutations although non significantly (8/27 vs 6/10, p=0.09), but there was a trend toward more frequent ER in case of HeRG mutations (6/12) than KCNQ1 or KCNJ2 mutations (2/11 and 0/4) (p=0.09). ER is very common in LQT pts and is related to the gender and to the heart rate but not to the corrected QT duration. ER does not seem to be correlated to cardiac events in this series but may be linked to some gene mutations. Further studies are needed for demonstrating additional mutations/ variants or the existence of an early transient voltage gradient due to altered kinetics in muted potassium channels with loss of function.