cardiovascular disorders
Early Repolarization Syndrome
Introduction
Early repolarization syndrome is a genetic disorder of cardiomyocyte ion channel function (channelopathy). Patients are predisposed to polymorphic ventricular tachycardia (VT) and ventricular fibrillation (VF). Diagnosis is by ECG. Some patients require an implantable cardioverter defibrillator (ICD). (See also Overview of Arrhythmias and Early repolarization refers to ECG findings typically including J-point elevation ≥ 0.1 mV, often with a slurred or notched appearance, followed by ST-segment elevation in 2 or more contiguous leads. This ECG pattern is not uncommon, as it occurs in about 5% to 10% of the population, especially in men, younger patients, and athletes. Most people with this early repolarization ECG pattern do not manifest arrhythmias. However, early repolarization is substantially more common in survivors of apparently idiopathic ventricular fibrillation (VF), and early repolarizationsyndromerefers to people with early repolarization on ECG who also have had symptomatic ventricular arrhythmias. The risk of arrhythmia is higher when the early repolarization pattern is in the inferior leads, the lateral leads, or both. Early repolarization syndrome appears to result from mutations that produce a Gain of function of outward potassium current channels OR Loss of function of inward sodium or calcium current channels These ion channel changes magnify the normal small transmural voltage gradients during the plateau phase of the action potential. These gradients produce a J-wave and J-point elevation on the ECG and predispose to polymorphic ventricular tachycardia which can degenerate into Ventricular Fibrillation (VF) . Prior to the VT/VF the early repolarization pattern may become more exaggerated and the VT/VF may be precipitated by an episode of myocardial ischemia. The polymorphic VT is often initiated by a short-long-short RR interval sequence (although this sequence is not specific for early repolarization syndrome): The first short RR interval is between a baseline beat (usually a normal beat) and a premature beat (usually a premature ventricular beat). The long RR interval is the post–extra-systolic pause and ends with a baseline beat (usually a normal beat). This pause is followed by a short RR interval when the VT begins. Early repolarization syndrome appears to be inheritable, but disease-specific gene mutations are rarely identified, suggesting that the disorder is often polygenic. The ventricular arrhythmias may cause palpitations, and/or cardiac arrest. Syncope may occur but is uncommon because VT that occurs with early repolarization syndrome rarely self-terminates (unlike with some other disorders that cause VT in which syncope is more common). 