J-wave syndromes: early repolarization pattern, Brugada syndrome, hypercalcemia and hypothermia
The J wave – also referred to as Osborn’s wave – is defined as a wave occurring at the J point (Figure 1). Conditions in which the J wave occurs may be referred to as J wave syndromes. J waves are typically most pronounced in the anterolateral (V3, V4, V5, V6) and inferior (II, aVF and III) leads. There are four principial causes of J waves, namely hypothermia, Brugada syndrome, early repolarization and hypercalcemia.
The ECG in Brugada syndrome
Brugada syndrome is a rare channelopathy (electrical disorder caused by mutations in cardiac ion channels) which predisposes the individual to syncope, ventricular arrhythmias (ventricular tachycardia, ventricular fibrillation) and sudden cardiac death. There are three types of ECG manifestations, referred to as type 1, type 2 and type 3 Brugada syndrome. Refer to Figure 2 for ECG example of type 1 Brugada syndrome (note the large J waves in V2–V3).
Type 1 Brugada syndrome reminds somewhat of right bundle branch block (RBBB) in leads V1–V3, but the QRS duration is not prolonged in leads V5–V6 (which is not consistent with RBBB, in which there must be wide QRS complexes). In type 1 Brugada syndrome, the ST segment elevation has a coved shape in V1, V2 or V3. The ST segment starts at the apex of the second R-wave and is downsloping. The T-wave is negative (inverted).
Early repolarization pattern
Early repolarization occurs in 5% to 10% of all males. It is less common among women (prevalence 2% to 4%). The condition has been recognized for decades, and it has been regarded as a benign form of ST segment elevation with slurring or notching at the J point. A notch at the J point is actually a J wave.
The term “early repolarization” was used to describe what appeared to be a premature repolarization on the ECG. As seen in Figures 3 and 4, the ST segment elevations are indeed associated with what appear to be an interruption in the QRS complex and initiation of repolarization. However, no study to date has been able to demonstrate that the repolarization is actually early and, moreover, this condition is associated with five times as great a risk of sudden cardiac death. The prefix “benign” must therefore not be used. The risk of sudden cardiac death is greatest if the early repolarization pattern occurs in the inferior limb leads (II, aVF and III).
ECG features of early repolarization
- The ST segment elevations are concave and most pronounced in the chest leads. T-waves have high amplitude.
- The hallmark of early repolarization is the end-QRS slurring or end-QRS notching (the notch is the J wave!).
An in-depth discussion regarding J wave syndromes are provided by Charles Antzelevitch. Note that Brugada syndrome and early repolarization are discussed separately here on ECGwaves.com.