Electrocardiographic marker of ventricular action potential triangulation (the simulation study).

Background: The aim of this simulation was to examine the utility of a novel ECG-based index of cardiac action potential (AP) triangulation, the Tstart-to-Tpeak (TsTp) interval-to-JTstart (JTs) interval ratio, for assessment of changes in AP profile imposed through variations in the duration of the plateau phase and the phase 3 repolarization.

Methods: ECGs were simulated using a realistic rabbit model based on experimental data. The AP plateau was measured at APD30, and the phase 3 was assessed as APD90-to-APD30 difference (AP durations at 90 % and 30 % repolarization, respectively).

Cardiac repolarisation indices are associated with oxygen consumption during maximal exercise test in highly-trained cross-country skiers.

The objective of this study was to test the vectorelectrocardiographic T-wave characteristics for their associations with oxygen consumption (VO) and physical performance during a maximal cardiopulmonary exercise test (CPET) in highly trained cross-country skiers. Male highly trained cross-country skiers ( = 30) performed the maximal CPET on the bicycle ergospirometric "Oxycon Pro" system with simultaneous oxygen consumption (VO) and electrocardiogram recording. The measurements were done at rest; the stage preceding anaerobic threshold (preAnT); peak load; and recovery.

Formation of a border ischemic zone depends on plasma potassium concentration.

Extracellular potassium concentration might modify electrophysiological properties in the border zone of ischemic myocardium. We evaluated the depolarization and repolarization characteristics across the ischemic-normal border under [K] variation. Sixty-four-lead epicardial mapping was performed in 26 rats ([K] 2.

Action potential morphology affects T-wave symmetry (simulation study).

Background: Assessing T-wave symmetry in addition to QT subintervals measurements can provide novel independent data about ventricular repolarization abnormalities linked with arrhythmogenesis. However, the causes of the changes of T-wave symmetry are not completely understood. In silico studies showed that the more symmetrical T-waves were associated with shorter action potential duration (APD) and larger dispersion of ventricular repolarization (DOR).

Terminal T-wave inversion predicts reperfusion tachyarrhythmias in STEMI.

Introduction: A reliable electrocardiographic predictor of ventricular fibrillation (VF) in patients with ST elevation myocardial infarction (STEMI) is lacking so far. Previous experimental/simulation study suggested a terminal T-wave inversion (TTWI) in ischemia-related ECG leads corresponding to anterior infarct localization as an independent predictor of reperfusion VF (rVF). This T-wave characteristic has never been tested as a rVF predictor in clinical settings.

Dispersion of ventricular repolarization: Temporal and spatial.

Repolarization heterogeneity (RH) is an intrinsic property of ventricular myocardium and the reason for T-wave formation on electrocardiogram (ECG). Exceeding the physiologically based RH level is associated with appearance of life-threatening ventricular arrhythmias and sudden cardiac death. In this regard, an accurate and comprehensive evaluation of the degree of RH parameters is of importance for assessment of heart state and arrhythmic risk.

ECG markers of local but not global increase in dispersion of ventricular repolarization (simulation study).

Background: An increase in local dispersion of repolarization (DOR) may contribute more to arrhythmogenesis as compared to changes of global DOR. The aim of this simulation study was to find ECG markers of local increase in DOR in conditions where global DOR remains normal.

Methods: In the framework of van Oosterom and Oostendorp ECGSIM model, the local DOR was increased in 10 different ventricular locations by (1) action potential duration (APD) shortening/lengthening both on epi- and endocardium, (2) epicardial APD shortening, and (3) endocardial APD shortening.

Multi-lead vs single-lead T -T interval measurements for prediction of reperfusion ventricular tachyarrhythmias.

Introduction: Electrocardiographic T -T interval (Tp-Te) is a promising marker for the prediction of ventricular tachycardia and/or ventricular fibrillation (VT/VF). The study was aimed to compare single-lead vs multilead Tp-Te variables as VT/VF predictors in experimental ischemia/reperfusion model.

Methods And Results: Computer simulations were done using the ECGSIM model with an ischemic region set in anterior left ventricular apex.

Repolarization in perfused myocardium predicts reperfusion ventricular tachyarrhythmias.

Background: Aim of the study was to find out which myocardial repolarization parameters predict reperfusion ventricular tachycardia and fibrillation (VT/VF) and determine how these parameters express in ECG.

Methods: Coronary occlusion and reperfusion (30/30min) was induced in 24 cats. Local activation and end of repolarization times (RT) were measured in 88 intramyocardial leads.

Effect of action potential duration on T-T interval, T-wave area and T-wave amplitude as indices of dispersion of repolarization: Theoretical and simulation study in the rabbit heart.

Background: The aim of the study was to differentiate the effect of dispersion of repolarization (DOR) and action potential duration (APD) on T-wave parameters being considered as indices of DOR, namely, Tpeak-Tend interval, T-wave amplitude and T-wave area.

Methods: T-wave was simulated in a wide physiological range of DOR and APD using a realistic rabbit model based on experimental data. A simplified mathematical formulation of T-wave formation was conducted.

Mechanism of electrocardiographic T-wave flattening in diabetes mellitus: experimental and simulation study.

In the present study we investigated the contribution of ventricular repolarization time (RT) dispersion (the maximal difference in RT) and RT gradients (the differences in RT in apicobasal, anteroposterior and interventricular directions) to T-wave flattening in a setting of experimental diabetes mellitus. In 9 healthy and 11 diabetic (alloxan model) open-chest rabbits, we measured RT in ventricular epicardial electrograms. To specify the contributions of apicobasal, interventricular and anteroposterior RT gradients and RT dispersion to the body surface potentials we determined T-wave voltage differences between modified upper- and lower-chest precordial leads (T-wave amplitude dispersions, TWAD).

The Role of Transmural Repolarization Gradient in the Inversion of Cardiac Electric Field: Model Study of ECG in Hypothermia.

Background: The changes in ventricular repolarization gradients lead to significant alterations of the electrocardiographic body surface T waves up to the T wave inversion. However, the contribution of a specific gradient remains to be elucidated. The objective of the present investigation was to study the role of the transmural repolarization gradient in the inversion of the body surface T wave with a mathematical model of the hypothermia-induced changes of ventricular repolarization.

Action potential duration gradients in the heart ventricles and the cardiac electric field during ventricular repolarization (a model study).

Background: We simulated contributions of transmural, apicobasal, anteroposterior and interventricular action potential duration (APD) gradients to the body surface potential distribution (BSPD) with constant or varied magnitudes of the transmural and apicobasal gradients.

Methods: Simulations were done in the framework of the discrete computer model of the rabbit heart ventricles on the basis of realistic activation sequence and APDs. The APD gradients were set constant at 20 ms or varied in the range of ±80 ms.

Functional role of myocardial electrical remodeling in diabetic rabbits.

The objective of the study was to investigate the role of electrical remodeling of the ventricular myocardium in hemodynamic impairment and the development of arrhythmogenic substrate. Experiments were conducted with 11 healthy and 12 diabetic (alloxan model, 4 weeks) rabbits. Left ventricular pressure was monitored and unipolar electrograms were recorded from 64 epicardial leads.

What does the T(peak)-T(end) interval reflect? An experimental and model study.

Background: It is unclear whether the Tpeak-Tend interval is an index of the transmural or the total dispersion of repolarization.

Methods: We examined the Tpeak-Tend interval using a computer model of the rabbit heart ventricles based on experimentally measured transmural, apicobasal, and interventricular gradients of action potential duration.

Results: Experimentally measured activation-recovery intervals increased from apex to base, from the left ventricle to the right ventricle, and in the apical portion of the left ventricle from epicardium to endocardium and from the right side of septum to the left side.

Ventricular repolarization pattern under heart cooling in the rabbit.

Aim: Prolongation of ventricular repolarization is characteristic of myocardial cooling. In the present study, we investigated whether this prolongation is uniform or not throughout ventricular epicardium and how these hypothermia-induced changes express in the body surface potential distribution.

Methods: Epicardial and body surface potential mapping from 64 unipolar leads was carried out in 18 anaesthetized adult rabbits.