CONTEXT Of the several factors implicated in causing QT interval prolongation and torsades de pointes, errors in the use of medications that may prolong this interval deserve special attention. OBJECTIVE To systematically summarize the available clinical data on the QT interval and to offer improved recommendations for the use of QT-prolonging medications. DATA SOURCES We searched MEDLINE f...

We quantified the repolarization time (so-called QT interval) in a rat, an animal species that does not show a well-characterized T wave on surface ECG. We used spontaneously hypertensive rats (SHR) and converting enzyme inhibition to demonstrate a reversible increase in QT interval in pressure-overloaded hearts in the absence of ischemia. An implanted telemetry system recording ECG data in fre...

BACKGROUND It is thought that the autonomic nervous system modulates QT interval, but traditional autonomic blockade combining propranolol and atropine has produced conflicting results. We used the alternative approach of interrupting neurotransmission at the level of autonomic ganglia to determine its effect on the QT interval. METHODS AND RESULTS We infused trimethaphan at increasing doses ...

OBJECTIVE To evaluate the changes in Tp-e interval (an interval from the peak to the end of the T wave), QT interval and Tp-e/QT ratio of the body surface ECG in patients with left ventricular hypertrophy (LVH). METHODS The Tp-e interval and QT interval were measured on body surface ECGs in 42 patients without either hypertension or LVH (control group), 41 patients having hypertension but not...

We examined the relationship between changes in heart rate and the measured QT interval of the electrocardiogram in healthy subjects after exercise and during breath holding, hyperventilation, the dive reflex, the Valsalva maneuver, and the cold-pressor test. The tachycardia of exercise was accompanied by the familiar shortening of the QT interval, but substantial heart rate changes encountered...

Abnormal prolongation and shortening of the electrocardiographic QT interval duration, which occur in the hereditary forms of long and short QT syndromes, are associated with an increased risk of ventricular arrhythmias and sudden cardiac death. Even within the normal range, these altered durations are associated with an increased mortality risk in the general population. While extreme prolonga...

BACKGROUND We set out to identify common genetic determinants of the length of the RR and QT intervals in 2325 individuals from isolated European populations. METHODS AND RESULTS We analyzed the heart rate at rest, measured as the RR interval, and the length of the corrected QT interval for association with 318 237 single-nucleotide polymorphisms. The RR interval was associated with common va...

OBJECTIVES The purpose of this study was to evaluate the efficacy of various antiarrhythmic drugs at prolonging the QT interval into the normal range and preventing ventricular arrhythmias in patients with short QT syndrome. BACKGROUND Short QT syndrome is a recently described genetic disease characterized by short QT interval, high risk of sudden death, atrial fibrillation, and short refract...

Evaluating whether a new medication prolongs QT intervals is a critical safety activity that is conducted in a sensitive animal model during non-clinical drug development. The importance of QT liability detection has been reinforced by non-clinical [International Conference on Harmonization (ICH) S7B] and clinical (ICH E14) regulatory guidance from the International Conference on Harmonization....