Normal Ventricular Repolarization and QT Interval : Ionic Background, Modifiers, and Measurements - 23/08/17

Doi : 10.1016/j.ccep.2017.05.007

Emanuela T. Locati, MD, PhD ^a,^⁎ , Giuseppe Bagliani, MD ^b,^c, Luigi Padeletti, MD ^d,^e
^a Electrophysiology Unit, Cardiology Division, Cardiovascular Department, ASST GOM Niguarda Hospital, Piazza Ospedale Maggiore, 3, 20162 Milano, Italy
^b Arrhythmology Unit, Cardiology Department, Foligno General Hospital, Via Massimo Arcamone, 06034 Foligno (PG), Italy
^c Cardiovascular Diseases Department, University of Perugia, Piazza Menghini 1, 06129 Perugia Italy
^d Heart and Vessels Department, University of Florence, Largo Brambilla, 3, 50134 Florence, Italy
^e IRCCS Multimedica, Cardiology Department, Via Milanese, 300, 20099 Sesto San Giovanni, Italy

^∗Corresponding author.

Résumé

The QT interval on surface electrocardiogram represents the sum of depolarization and repolarization process of the ventricles. The ventricular recovery process, reflected by ST segment and T wave, mainly depends on the transmembrane outward transport of potassium ions to reestablish the endocellular electronegativity. Outward potassium channels represent a heterogeneous family of ionic carriers, whose global kinetics is modulated by heart rate and autonomic nervous activity. Several cardiac and noncardiac drugs and disease conditions, and several mutations of genes encoding ionic channels, generating distinct genetic channellopathies, may affect the ventricular repolarization, provoke QT interval prolongation and shortening, and increase the susceptibility to ventricular arrhythmias.

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Keywords : Ventricular repolarization, QT interval, J point, ST segment, T wave, U wave, Electric memory, T wave alternans