QT interval prolongation is associated with a risk of polymorphic ventricular tachycardia. QT interval shortens with increasing heart rate and correction for this effect is necessary for meaningful QT interval assessment. We aim to improve current methods of correcting the QT interval during atrial fibrillation (AF). Digitized Holter recordings were analyzed from patients with AF. Models of QT ...

Let (Qt) M 0 be a random Q -process, that is let Q0 be the empty spanning subgraph of the cube Q n and, for 1 ≤ t ≤ M = nN/2 = n2n−1, let the graph Qt be obtained from Qt−1 by the random addition of an edge of Q not present in Qt−1. When t is about N/2, a typical Qt undergoes a certain ‘phase transition’: the component structure changes in a sudden and surprising way. Let t = (1 + )N/2 where is...

Suggestions were made that increased myocardial sympathetic activity is reflected by elevated QT variability (dynamic changes in QT interval duration). However, the relationship between QT variability and the amount of norepinephrine released from the cardiac sympathetic terminals is unknown. We thus attempted to assess this relationship. The study was performed in 17 subjects (12 with major de...

OBJECTIVES The intra-pulmonary shunt induced by one-lung ventilation (OLV), is alleviated by increased pulmonary blood flow by gravitational redistribution and hypoxic pulmonary vasoconstriction. We investigated the changes of pulmonary venous blood flow (PVBF) and biventricular function during OLV with echocardiography. And the correlation between PVBF and intra-pulmonary shunt fraction (Qs/Qt...

Electrocardiographic study of 50 healthy Markhoz goats ranging from less than 1 to more than 3 years inage was carried out. The heart rate varied from 99 to 123 beats/min with a mean of 110 beats/min. There wasa significant difference between the heart rate of goats in 3 age groups (PT waves and QT interval in base apex lead, QRS wave in lead I, P-R and PQ interval in aVF lead were higherand du...

The QT interval reflects the time between the depolarization of ventricles until their repolarization and is usually used as a predictive marker for the occurrence of arrhythmias. This parameter varies with the heart rate, expressed as the RR interval (time between two successive ventricular depolarizations). To calculate the QT independently of the RR, correction formulae are currently used. I...

OBJECTIVE A clinical trial was conducted in healthy adult volunteers to assess the effect of levofloxacin, moxifloxacin, and ciprofloxacin on the QT and QTc interval. METHODS Electrocardiograms were recorded 24 hours before and after subjects took placebo, 1000 mg levofloxacin, 800 mg moxifloxacin, and 1500 mg ciprofloxacin in a double-blind, randomized, 4-period, 4-treatment, 4-sequence cros...

Historically, the heart rate corrected QT (QTc) interval has been the standard method to assess for impaired ventricular repolarization, particularly for drug development. However, QTc does not reflect changes in autonomic state or QT-RR hysteresis which can also affect the interpretation of arrhythmogenic risk. With the advent of more accurate algorithms to automatically measure the QT interva...

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...