Abstract

The frequency of early repolarization in the general population is approximately 5%, but this may vary with age, sex, race, and the criteria used to define the term.1,2 Early repolarization commonly is identified on an electrocardiogram (ECG) by the presence of a J wave, J point elevation, and tall symmetrical T waves with concave ST segment elevation in 2 contiguous leads. Historically, early repolarization has been considered a benign normal variant observed most commonly in the left precordial leads and is most prevalent in athletes and adolescents.1–3 Early repolarization is also more common in African Americans than in other races.1–3 Recently, there have been reports of an association between early repolarization and idiopathic ventricular tachycardia, especially in the presence of J waves and horizontal ST-segment depression.1,4,5 In addition, there have been reports of increased risk of sudden cardiac death in patients who have early repolarization in the inferolateral leads.5The J wave (also known as Osborne wave) is a deflection occurring at the end of the QRS complex that has similar morphology to the P wave and may be observed in patients who have hypothermia or other conditions such as Brugada Syndrome. When present, the J wave usually is seen in all 12 leads.6The J point is the point at the junction between the QRS complex and the beginning of the ST segment. J point elevation occurs when the J point is above baseline. The J point may be elevated in healthy people or patients who have pathologic conditions such as myocardial infarction or pericarditis. The normal limits of J point elevation may vary with ECG lead, QRS amplitude, patient age, sex, and race.6Early repolarization is commonly used to describe a normal QRS-T variant with J point elevation.7 Early repolarization is generally defined as J point elevation manifested by QRS slurring (at the transition between the QRS complex and ST segment) or notching (a positive deflection in the terminal S wave) with concave ST-segment elevation and prominent T waves in at least 2 contiguous leads. The criteria for ST-segment or J point elevation typically is 0.1 mV, but various definitions have been used historically to define early repolarization.1Surawicz and Macfarlane6 note that the term early repolarization is confusing and unnecessary, arguing that it should not be used with descriptions of ECGs. Instead, they believe that existing ECG terminology (eg, ST-segment elevation and duration) should be used when describing ECG findings.6 Furthermore, Surawicz and Macfarlane argue that the J wave is part of the ST segment and rarely observed in patients who do not have hypothermia.6 However, Antzelevitch and colleagues8 provide rationale for using the terms early repolarization and J wave syndrome in identifying people who are at high risk for adverse events.In a population study of persons of Central European descent,9 early repolarization occurred in 13% of participants. The participants were aged 35 to 74 years and studied for an average of 18.9 years each. Early repolarization was associated with increased cardiac and all-cause mortality, with the risk of dying greater in men aged 35 to 54 years (hazard ratio, 2.65).9A case-control study showed that the presence of J waves is associated with an increased risk of developing idiopathic ventricular tachycardia (odds ratio, 4.0), especially for J waves with horizontal ST segments (odds ratio, 13.8).4 In cardiac arrest survivors who had normal left ventricular ejection fraction, early repolarization in the inferolateral leads was observed in 19% of all patients and 23% of patients who had no diagnosis to explain the cardiac arrest.10In a study of atomic bomb survivors,11 early repolarization was present in 24% of the population and was associated with an increased risk of dying unexpectedly and a decreased risk of cardiac and all-cause mortality.11 Furthermore, QRS slurring or notching and early repolarization pattern in inferior and lateral leads were associated with a statistically significant higher risk of unexpected death. In this study, early repolarization was defined as 0.1 mV or greater ST elevation or J point elevation in at least 2 inferior or lateral leads.11Watanabe and colleagues12 found that early repolarization is more common in patients who have short QT syndrome than in control subjects with short QT interval and no arrhythmic events or with normal QT interval. The researchers also found early repolarization (not the QT interval) to be associated with arrhythmias, concluding that the presence of early repolarization may be helpful in predicting the risk of cardiac events in patients who have short QT syndrome.12Some studies have not shown an associated risk of developing cardiovascular events in people who have early repolarization. For example, in a study of 704 athletes, early repolarization frequently was associated with other ECG changes but not adverse cardiac events such as tachyarrhythmias and sudden death.13 A prospective cohort study of 5039 patients evaluated at 0, 7, and 20 years showed no increased risk associated with early repolarization in any subgroup (race, sex, age) except for in blacks.14 However, in a meta-analysis of 9 studies, early repolarization was associated with an increased risk ratio of 1.7 for death related to arrhythmia (P = .003). The estimated absolute risk difference for people who had early repolarization was 70 cases of death from arrhythmia per 100 000 persons per year.15In response to reports that challenged early repolarization as a benign normal variant and to the controversies over the criteria for defining early repolarization, a consensus paper was published that provides terminology, measurements, and new definitions for early repolarization and associated terms (Tables 1 and 2).16 Recommendations also were included for measurements related to the components of early repolarization.16 In the new definition, if the ST segment slopes upward and is accompanied by an upright T wave, the pattern is described as early repolarization with an ascending ST segment. If there is a horizontal or downward sloping ST segment, the pattern is described as early repolarization with a horizontal or descending ST segment. An ECG that has ST-segment elevation without a slur or notch should not be reported as early repolarization.16 An ECG showing early repolarization pattern in leads II, III, aVF, and V4–V6 (inferolateral leads) might have evidence of an end QRS notch in lead V4 and end QRS slur in lead III (see Figure). This pattern is described as early repolarization with an ascending ST segment because the ST segment slopes upward and is followed by an upright T wave.Early repolarization traditionally was considered a benign ECG variant; however, early repolarization in the inferior or lateral leads may be associated with an increased risk of adverse events including arrhythmias and sudden cardiac death.1,3,9–12,15 A recent consensus paper addresses the importance of accurately identifying people at risk, corrects inconsistences in criteria previously used to define early repolarization, and provides guidance with terminology, measurements, and consistent criteria to identify early repolarization.16 Consistency in definition of the terminology will support ongoing research about the prevalence and risks associated with early repolarization and strategies for risk reduction.

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