The phenomenon of "qT stunning": The abnormal QT prolongation provoked by standing persists even as the heart rate returns to normal in patients with long QT syndrome

Abstract

Background: Patients with long QT syndrome (LQTS) have inadequate shortening of the QT interval in response to the sudden heart rate accelerations provoked by standing - a phenomenon of diagnostic value. We now validate our original observations in a cohort twice as large. We also describe that this abnormal QT-interval response persists as the heart rate acceleration returns to baseline. Objectives: To describe a novel observation, termed "QT stunning" and to validate previous observations regarding the "QT-stretching" phenomenon in patients with LQTS by using our recently described "standing test." Methods: The electrocardiograms of 108 patients with LQTS and 112 healthy subjects were reco..