Early repolarization syndrome: A cause of sudden cardiac death

Abstract

Early repolarization syndrome (ERS), demonstrated as J-point elevation on an electrocardiograph, was formerly thought to be a benign entity, but the recent studies have demonstrated that it can be linked to a considerable risk of life - threatening arrhythmias and sudden cardiac death (SCD). Early repolarization characteristics associated with SCD include high - amplitude J-point elevation, horizontal and/or downslopping ST segments, and inferior and/or lateral leads location. The prevalence of ERS varies between 3% and 24%, depending on age, sex and J-point elevation (0.05 mV vs 0.1 mV) being the main determinants. ERS patients are sporadic and they are at a higher risk of having recurrent cardiac events. Implantable cardioverter-defibrillator implantation and isoproterenol are the suggested therapies in this set of patients. On the other hand, asymptomatic patients with ERS are common and have a better prognosis. The risk stratification in asymptomatic patients with ERS still remains a grey area. This review provides an outline of the up-to-date evidence associated with ERS and the risk of life - threatening arrhythmias. Further prospective studies are required to elucidate the mechanisms of ventricular arrhythmogenesis in patients with ERS.

Keywords: Early repolarization; Early repolarization syndrome; J-wave; Sudden cardiac death.

Figure 1

Examples of the classic and new definitions of early repolarization. Examples of the original (classic) and emerging (new) definitions of early repolarization (ER). A and B show the classic form of STE-type ER, which is the form identified by ECG software algorithms. Notice the presence of a J wave in (B), followed by an ascending/upsloping ST segment. Both forms are considered benign; C and D show the malignant form of ER demonstrated as slurring at the end of QRS complex (C) or a discrete notch/J wave (D) followed by a horizontal/downslopping ST segment (no ST elevation). Reproduced from ref.[49], with permission from the publisher. STE: ST elevation type ER; ECG: Electrocardiographic.

Figure 2

Schematic representation of the possible mechanisms underlying J-wave occurrence. Action potentials from epicardium and endocardium from normal individuals (left) and early repolarization (ER) patients (right) as well as the respective electrocardiograms are shown. A prominent phase I-notch and the loss of epicardial dome in phase - 2 (thick arrow) results in transmural dispersion of repolarization (dashed arrows) and appearance of the J-wave and ST-segment elevation on the surface ECG. AP: Action potential; ECG: Electrocardiogram; ER: Early repolarization; RP: Resting potention. Reproduced with permission, from ref.[67].

Figure 3

Benign early repolarization: Electrocardiogram showing ST segment elevation by at least 0.1 mV from the baseline. Reproduced with permission, from ref.[68].

Figure 4

Malignant early repolarization: J-wave elevation (arrows) as slurring (lead II) and notching in the inferior and lateral leads and ascending ST segment in most leads. Reproduced with permission, from ref.[69].

Figure 5

Brugada electrocardiogram-types. Type-1 is characterized by a complete or incomplete right bundle-branch block pattern with a coved morphology ST-segment elevation of ≥ 2 mm in the right precordial leads (V1-V3) followed by a negative T-wave. In type-2, ST-segment elevation has a saddleback appearance with a high takeoff ST-segment elevation of > 2 mm, a trough displaying > 1-mm ST-elevation followed by a positive or biphasic T-wave. Type-3 has an ST-segment morphology that is either saddleback or coved with an ST-segment elevation of < 1 mm. Reproduced with permission, from ref.[69].

Figure 6

Malignant early repolarization: Horizontal ST-segment after early repolarization.