Dissecting the Genetic Basis of the ECG as a Means of Understanding Mechanisms of Arrhythmia.

Abstract

The surface ECG records the electrical potential of the heart at the surface of the body as the electrical impulse travels throughout the heart with each heartbeat. The P wave represents depolarization of the atria, which spreads from the sinoatrial node toward the atrioventricular node and from the right to the left atrium. The PR interval reflects the time the electrical impulse takes to travel from the sinus node through the atrioventricular node. The QRS complex represents the rapid depolarization of the ventricles, and the T wave represents the repolarization of the ventricles. See Article by Christophersen et al The ECG is one of the most accessible and valuable diagnostic tests. It informs about the presence of cardiac chamber enlargement/hypertrophy, conduction disturbance, arrhythmia, myocardial infarction/ischemia, and even provides indications for electrolyte imbalance or drug intoxication. Since about a decade, researchers have turned to the ECG as a tool to dissect the genetic basis of cardiac electrical function with the idea that the biological processes that underlie or impinge on the different parameters of the ECG are mediators (intermediate phenotypes, endophenotypes) of arrhythmia risk.1 This concept, which in itself is clearly intuitive, is supported by population-based studies that demonstrated that ECG parameters are associated with risk of arrhythmia or sudden cardiac death.2 The approach is furthermore rationalized by the fact that ECG parameters have been shown to have a heritable component (reviewed in reference3). The first ECG parameter that was studied in this way by the genome-wide association study (GWAS) approach was the QT interval1; in fact the QT interval was one of the first traits to be studied at the outset of the GWAS era 10 years ago.4 Facilitated by the availability of large cohorts with ECG recordings and the ability to measure ECG …