Early Repolarization

Early repolarization is a syndrome typically seen in healthy patients <50 years old. Because it causes repolarization abnormality, it often adds additional complexity in patients presenting with chest pain. Although it is not completely understood, it is thought to be a normal variant more commonly seen in those of African heritage. It used to be known as benign early repolarization, but many are suggesting the change to early repolarization as some studies have shown that patients have a slightly higher risk of sudden cardiac death with this syndrome.

The EKG changes with early repolarization include concave ST elevation, J point notching, and asymmetric though somewhat prominent T waves. These changes are seen most prominently in the V2-V6, though commonly seen to some degree diffusely. The ST elevations are usually <2mm in the precordial leads (ST elevation may be present in limb leads and should be <0.5mm) and should not have reciprocal ST depressions. However, sometimes the elevations may reach up to (but less than) 5mm; these larger ST elevations are typically seen with very large R wave amplitudes. Additionally, the amplitude of ST elevation is modest in comparison to the amplitude of the T waves (<25%). If serial EKG's are obtained in the ED, there should not be dynamic changes. However, slower heart rates tend to produce somewhat higher degree of ST elevations (and tachycardia tends to resolve or nearly resolve the ST elevations). The T waves are asymmetric, with the ascending limb being concave and the descending limb being more straight (usually compared to a smile). Sometimes, the J point notching is referred to as a fish hook pattern; it is usually best seen in lead V4.

In contrast to OMI, the T wave morphology is asymmetric with early repolarization. Furthermore, there are not dynamic changes. Additionally, early repolarization typically has a short QT (myocardial ischemia commonly prolongs the QT). ST elevation >5mm is highly indicative of OMI vs ER. Terminal QRS distortion is also indicative of OMI. Furthermore, Q waves in V2-4 are more indicative of MI. 

Steve Smith has also made a 4 formula to help differentiate LAD occlusion from early repolarization that has been validated. The inclusion criteria is at least 1mm ST elevation at the J point of V2-V4. The exclusion criteria are wide QRS, ST elevation>5mm, convex ST elevation, Q waves in V2-V4, reciprocal ST depression, and terminal QRS distortion in V2 or V3. The 4 factor formula relies on the QTc, QRS amplitude in V2 (QRSV2), R wave amplitude in V4 (RAV4), and ST segment elevation 60ms after the J point in V3 (STE60V3). It can be found here on MDCalc: https://www.mdcalc.com/subtle-anterior-stemi-calculator-4-variable. A value greater than 18.2 is indicative of LAD occlusion. The further away from this number, the more accurate the result. 

Examples:

Further Reading:

https://litfl.com/benign-early-repolarisation-ecg-library/

http://hqmeded-ecg.blogspot.com/search/label/early%20repolarization

http://hqmeded-ecg.blogspot.com/search/label/LAD%20occlusion%20vs.%20benign%20early%20repolarization