Early repolarization with horizontal ST segment may be associated with aborted sudden cardiac arrest: a retrospective case control study

Background Risk stratification of the early repolarization pattern (ERP) is needed to identify malignant early repolarization. J-point elevation with a horizontal ST segment was recently suggested as a malignant feature of the ERP. In this study, the prevalence of the ERP with a horizontal ST segment was examined among survivors of sudden cardiac arrest (SCA) without structural heart disease to evaluate the value of ST-segment morphology in risk stratification of the ERP. Methods We reviewed the data of 83 survivors of SCA who were admitted from August 2005 to August 2010. Among them, 25 subjects without structural heart disease were included. The control group comprised 60 healthy subjects who visited our health promotion center; all control subjects were matched for age, sex, and underlying disease (diabetes mellitus, hypertension). Early repolarization was defined as an elevation of the J point of at least 0.1 mV above the baseline in at least two continuous inferior or lateral leads that manifested as QRS slurring or notching. An ST-segment pattern of <0.1 mV within 100 ms after the J point was defined as a horizontal ST segment. Results The SCA group included 17 men (64%) with a mean age of 49.7 ± 14.5 years. The corrected QTc was not significantly different between the SCA and control groups (432.7 ± 37.96 vs. 420.4 ± 26.3, respectively; p = 0.089). The prevalence of ERP was not statistically different between the SCA and control groups (5/25, 20% vs. 4/60, 6.7%, respectively; p = 0.116). The prevalence of early repolarization with a horizontal ST segment was more frequent in the SCA than in the control group (20% vs. 3.3%, respectively; p = 0.021). Four SCA subjects (16%) and one control subject (1.7%) had a J-point elevation of >2 mm (p = 0.025). Four SCA subjects (16%) and one (1.7%) control subject had an ERP in the inferior lead (p = 0.025). Conclusion The prevalence of ERP with a horizontal ST segment was higher in patients with aborted SCA than in matched controls. This result suggests that ST morphology has value in the recognition of malignant early repolarization.