The dependence on heart rate of the QT interval has been investigated for many years and several mathematical formulae have been proposed to describe the QT interval/heart rate (or QT interval/RR interval) relationship. While the most popular is Bazett's formula, it overcorrects the QT interval at high heart rates and under-corrects it at slow heart rates. This formulae and many others similar ...

OBJECTIVE To study QT dispersion in left ventricular hypertrophy and chronic heart failure and to determine the relation to ventricular arrhythmias. SETTING Investigational laboratory of a tertiary referral centre. STUDY DESIGN Patients with left ventricular hypertrophy and normal systolic function (n = 14) and patients with chronic heart failure (n = 18) were matched with controls (n = 17)...

BACKGROUND Quercetin (QT) is a potential bioflavonol and antioxidant with poor bioavailability and very low distribution in the brain. A new oral delivery system comprising of poly(n-butylcyanoacrylate) nanoparticles (PBCA NPs) was introduced to improve the oral bioavailability of QT and to increase its distribution in the brain. Physicochemical characteristics, in vitro release, stability in s...

Mitral valve prolapse (MVP) is a relatively frequent valvular abnormality. In both children and adults with MVP, an increased incidence of ventricular arrhythmias has been reported. QT dispersion, defined as the difference in duration between the longest QT interval and the shortest one, for a given set of electrocardiographic leads has been proposed as a sign of regional difference in card...

Background: Passive cigarette smoking is a known cause of a variety of diseases.  However, most of the studies done in this field have focused on its chronic effects on human health.  Studies considering the acute effect of smoking on QT dispersion, on the other hand, with its known predictive role in the occurrence ventricular arrhythmia and sudden cardiac death are sparse. Objectives: This st...

background anthracyclines are important components of many chemotherapeutic protocols. the present study aimed to evaluate the repolarization changes in electrocardiography (ecg) which may predict drug induced arrhythmia. materials and methods in this cross-sectional study, the recorded ecgs were assessed for qt dispersion (qtd), qt corrected dispersion (qtcd), t peak to tend dispersion (tped),...

Abnormal left ventricular structure and function as in, for example, left ventricular hypertrophy or chronic heart failure, is associated with sudden cardiac death and, when the ejection fraction is depressed, with prolongation of the QT interval. The dependence on heart rate of QT interval prolongation in these conditions, and the relationship of any abnormalities either to deranged autonomic ...

This study investigated beat-to-beat QT variability in patients with panic disorder and depression, and normal control subjects using an automated algorithm to compute QT intervals. An increase in QT variability appears to be associated with symptomatic patients with dilated cardiomyopathy and also with an increased risk for sudden death. QT(vm) (QT variability normalized for mean QT interval) ...