Clinical Significance of Early Repolarization in Long QT Syndrome

This study sought to determine the prevalence of early repolarization pattern (ERP) within a large cohort of patients with long QT syndrome (LQTS) and examine the correlation and clinical significance of ERP with symptomatic status and subsequent risk of breakthrough cardiac events (BCEs).

The electrocardiographic ERP is associated with an increased risk of arrhythmic events and sudden cardiac death.

ERP was defined as an end-QRS notch or slur on the downslope of a prominent R-wave with a J point ≥0.1 mV in 2 or more contiguous leads of the 12-lead electrocardiogram, excluding V1 to V3. A patient was considered previously symptomatic if they had a suspected LQTS-triggered cardiac event prior to diagnosis. BCEs were defined as LQTS-attributable syncope/seizures, aborted cardiac arrest, appropriate ventricular fibrillation-terminating implantable cardioverter-defibrillator shocks, and sudden cardiac death following diagnosis and institution of a LQTS-directed treatment program.

In this study, 528 patients (57% female) with genotype-confirmed LQTS (283 with LQT1, 193 with LQT2, and 52 with LQT3) were reviewed from which 2,618 electrocardiograms were analyzed over a median follow-up of 6.7 (interquartile range, 3.6 to 10 years) years. Eighty-two (15.5%; female 51%) patients were identified as having ERP; 40 (50%) of these ERP-positive patients showed persistent ERP. One hundred twenty-four patients (23.5%) were classified as previously symptomatic LQTS and 39 (7.2%) experienced a subsequent BCE. ERP was not associated with either symptomatic status (p = 0.62) or BCE (p = 0.61).

Although ERP is common in LQTS, this extensive study suggests that the presence of concomitant ERP does not correlate with either those with a history of LQTS-triggered events prior to diagnosis or those with subsequent BCEs from their treated LQTS substrate.