The response of the QT interval to the brief tachycardia provoked by standing: a bedside test for diagnosing long QT syndrome.

Objectives: This study was undertaken to determine whether the short-lived sinus tachycardia that occurs during standing will expose changes in the QT interval that are of diagnostic value.

Background: The QT interval shortens during heart rate acceleration, but this response is not instantaneous. We tested whether the transient, sudden sinus tachycardia that occurs during standing would expose abnormal QT interval prolongation in patients with long QT syndrome (LQTS).

J-point elevation in survivors of primary ventricular fibrillation and matched control subjects: incidence and clinical significance.

Objectives: The purpose of this study was to determine whether J-point elevation is a marker of arrhythmic risk.

Background: J-point elevation has been considered an innocent finding among healthy young individuals (the "early repolarization" pattern). However, this electrocardiogram (ECG) finding is increasingly being associated with idiopathic ventricular fibrillation (VF).