To evaluate whether heart-rate-induced changes of the QT interval are dependent on autonomic tone, we studied 13 healthy subjects, mean age 67.5 years. The maximal uncorrected QT from leads I, II, V1 and V6 was determined during atrial pacing at 90 beats/min and 130 beats/min before and after i.v. administration of propranolol, 0.1 mg/kg, and atropine, 0.02 mg/kg. Significant reductions (p less...

Local repolarization changes in the myocardium can be noninvasively identified by an inverse solution using multichannel measurements of ECG potentials and QT integral maps in situation with and without changed repolarization. In this study, possible error of the inverse solution due to heart rate changes between the two measurements was analyzed on a model. Minimization of the error by compens...

Several QT correction (QTc) formulas have been used for assessing the QT liability of drugs. However, they are known to under- and over-correct the QT interval and tend to be specific to species and experimental conditions. The purpose of this study was to determine a suitable formula for halothane-anesthetized dogs highly sensitive to drug-induced QT interval prolongation. Twenty dogs were ane...

BACKGROUND Universal QT correction formulae have been shown to under or overcorrect the QT interval duration. Individual QT-R-R modeling has been proposed as a preferable solution for heart rate correction of QT intervals. However, the QT-R-R relationship stability over time needs to be evaluated. METHODS The present report is part of randomized, double-dummy, and placebo-controlled 4-way cro...

We report on an asymptomatic 10-year-old boy who had a short QT interval (corrected QT interval, 260 ms). Short QT syndrome (SQTS) was detected in a school screening program for heart disease and the patient was subsequently diagnosed as having N588K mutation in the KCNH2 gene. Quinidine prolonged the QT interval, but not the QU interval. During treadmill exercise stress test, QT and QU interva...

Alterations in ECG QT intervals correlate with the risk of potentially fatal arrhythmias, for which transgenic murine hearts are becoming increasingly useful experimental models. However, QT intervals are poorly defined in murine ECGs. As a consequence, several different techniques have been used to measure murine QT intervals. The present work develops a consistent measure of the murine QT int...

Introduction In inherited long QT syndrome (LQTS), female sex is associated with a longer QT interval duration and a higher risk for potentially lethal polymorphic ventricular tachycardia (pVT) and sudden cardiac death than in males. The arrhythmogenic risk is particularly pronounced during the postpartum period—especially in patients with LQTS type 2—but relatively low during pregnancy, indica...

We analyzed the QT and RR interval time series continuously recorded during 90 degrees passive Tilt test in 10 young healthy subjects (age 2625 years, 5 females). Changes in QT interval were assessed on 1 minute time related templates and on rate-independent waveforms obtained by averaging beats preceded by the same RR interval. Following Tilt, the mean RR interval shortened from 927273 ms to 7...

INTRODUCTION It is believed that an exaggerated blood pressure response (EBPR) to exercise stress test is associated with a higher risk of cardiovascular events. It is also assumed that QT dispersion (QT-d), which was originally proposed to measure the spatial dispersion of ventricular recovery times, may have a relationship to cardiovascular events. The objective of this study was to examine t...

Prolongation of the QT interval of the ECG represents an imbalance in cardiac autonomic function and may predict cardiac arrhythmia. Vagal activity protects against prolongation of the QT interval which may be associated with flattening of the T-wave of the ECG. The changes in QT interval, T-wave amplitude and respiratory sinus arrhythmia (RSA) were studied after i.v. administration of atropine...