Clinical Significance of Early Repolarization in Long QT Syndrome

Abstract

Objectives: 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).

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

Methods: 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.

Results: 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).

Conclusions: 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.

Keywords: breakthrough cardiac events; early repolarization; electrophysiology; long QT syndrome.