Effect of atrial artificial electrical stimulation on depolarization and repolarization and hemodynamics of the heart ventricle in rainbow trout Oncorhynchus mykiss.

The spatial-temporal organization of the activation, repolarization and hemodynamics of the heart ventricle in rainbow trout, Oncorhynchus mykiss, adapted to a temperature of 5-7 °C, were studied from the normal sinus rhythm (21.6 ± 4.9 bpm) to the highest possible heart rhythm (HR) (60 bpm), during which deterioration of the contractile activity of the myocardium occurred.

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.

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.

Effects of echinochrome on ventricular repolarization in acute ischemia.

Background: Myocardial ischemic electrophysiological alterations are associated with the generation of reactive oxygen species. However, electrophysiological effects of antioxidants are unclear. Our objective was to determine the effects of the antioxidant echinochrome on ventricular repolarization in a feline model of 30-min ischemia.

Ventricular repolarization in a rat model of global heart failure.

Isoproterenol in high doses induces infarction-like myocardial damage and structural and functional remodelling of the ventricular myocardium. The purpose of the present study was to investigate ventricular repolarization in a rat model of isoproterenol-induced heart failure. Isoproterenol was administered twice to female Wistar rats (170 mg/kg, s.

Doxorubicin-induced changes of ventricular repolarization heterogeneity: results of a chronic rat study.

Anthracycline chemotherapy produces cardiac repolarization abnormalities and arrhythmias because of cardiac toxicity of drugs. Ventricular arrhythmogenesis is attributable to increase in repolarization heterogeneity that is characterized by spatial dispersion of repolarization. The purpose of this work was to study the delayed effects of doxorubicin, the most frequently used anthracycline, on repolarization heterogeneity of the ventricular epicardium.

Remodeling of ventricular repolarization in a chronic doxorubicin cardiotoxicity rat model.

Doxorubicin, one of the most effective anticancer drugs, is characterized by severe cardiotoxic effects, which induce cardiac remodeling and congestive heart failure. The aim of the study was to evaluate remodeling of ventricular repolarization heterogeneity in chronic doxorubicin cardiotoxicity in rats. Doxorubicin cardiotoxicity was produced by six equal intraperitoneal injections of the drug in a cumulative dose of 15 mg/kg in a 2-week period.

Acute effects of pacing site on repolarization and haemodynamics of the canine ventricles.

Aims: To determine the repolarization duration gradients in different ventricular regions at atrial and ventricular pacing and to test the hypothesis that acute haemodynamic response to ventricular pacing is related to the lead position with respect to repolarization gradients.

Methods And Results: Repolarization durations estimated as activation-recovery intervals (ARIs) were measured from unipolar electrograms recorded in the subepicardial (Epi), mid-myocardial (Mid), and subendocardial (Endo) layers of the apical and basal parts of the right ventricle (RV) and left ventricle (LV) of 15 healthy dogs under atrial and ventricular pacing. Cardiac haemodynamic variables were measured as well.

The contribution of ventricular apicobasal and transmural repolarization patterns to the development of the T wave body surface potentials in frogs (Rana temporaria) and pike (Esox lucius).

The study aimed at the simultaneous determination of the transmural and apicobasal differences in the repolarization timing and the comparison of the contributions of these two repolarization gradients to the development of the body surface T wave potentials in animals with the single heart ventricle (fishes and amphibians). Unipolar potentials were measured on the body surface, epicardium and in the intramural (subepicardial, Epi; midmyocardial; and subendocardial, Endo) ventricular layers of 9 pike and 8 frogs. Activation times, repolarization times and activation-recovery intervals were determined.

The effects of renovascular hypertension on repolarization of ventricular epicardium.

Background And Objective: Alterations in the recovery sequence of hypertrophied myocardium favour the development of cardiac arrhythmias. The aim of the present study was to investigate apex-to-base and interventricular heterogeneities in the duration of epicardial ventricular repolarization in rats with renovascular hypertension.

Method: Renovascular hypertension was induced in six Wistar rats by constricting the left renal artery for one month.

Characterization of systolic intervals in healthy, conscious sheep.

Objective: To characterize systolic intervals of the left ventricle and their relationship with heart rate in conscious sheep. Animals-11 healthy Romanov sheep (age range, 3 months to 10 years).

Procedures: Systolic intervals and indices of myocardial contractility of the left ventricle were measured in conscious sheep by use of polycardiography.

Activation pattern of the avian left ventricle during ventricular pacing.

Objective: This study was planned to investigate ventricular myocardial excitation in birds in which Purkinje fibres penetrate into the ventricular wall and reach the epicardium to advance our knowledge about the evolution of the ventricular activation process in vertebrates.

Methods: A depolarization pattern of the left ventricular free wall in seven open-chest laying hens was mapped by 14 seven-electrode plunge needles under ventricular pacing from different sites.

Results: Duration of activation of the left ventricular free wall is significantly increased during ventricular ectopic excitation as compared with sinus rhythm.

Effect of the left ventricular overload on epicardial repolarization in the rabbit.

Objective: We have investigated the local durations and sequence of repolarization in the ventricular epicardium in the rabbit under the increase of the left ventricular (LV) afterload.

Methods: The LV overload was produced by the 1-minute aortic stenosis up to systolic blood pressure of 140 mm Hg. The experiments were carried out on eight anaesthetized rabbits (urethane, 1.

Activation and repolarization patterns in the ventricular epicardium under sinus rhythm in frog and rabbit hearts.

Our study compared the contributions of activation sequence and local repolarization durations distribution in the organization of epicardial repolarization in animals with fast (rabbit) and slow (frog) myocardial activation under sinus rhythm. Activation times, repolarization times and activation-recovery intervals (ARI) were obtained from ventricular epicardial unipolar electrograms recorded in 13 Chinchilla rabbits (Oryctolagus cuniculus) and 10 frogs (Rana temporaria). In frogs, depolarization travels from the atrioventricular ring radially.

Left ventricular myocardal activation under ventricular paced beats in chickens Gallus gallus domesticus.

The aim of the study was to advance our knowledge regarding the activation process of the ventricular myocardium in birds in which Purkinje fibres penetrate into the ventricular wall to reach the epicardium. A depolarization pattern of the left ventricular free wall was studied in chickens (Gallus gallus) during ventricular paced beats. Duration of the activation process of the left ventricular free wall is significantly increased during ventricular ectopic excitation as compared with sinus rhythm.

Myocardial contractility in chickens (Gallus gallus): analysis of systolic time intervals.

The avian cardiovascular system is of special interest because avian hearts are relatively larger than mammalian hearts, and activation of ventricular myocardium in birds has a "flash" pattern. Systolic time intervals and indices of myocardial contractility were examined in anaesthetized open-chest chickens by polycardiography, including synchronous recordings of electrocardiogram, phonocardiogram, and apex cardiogram. The asynchronous contraction time, isometric contraction time, pre-ejection period and ejection time were 26 +/- 3 (Mean +/- SD), 21 +/- 9, 47 +/- 12, and 83 +/- 23 ms, respectively, for heart rates of 260 +/- 57 bpm.

P-wave body surface potential distribution in rats.

The aim of this study was to investigate body surface potential distribution during the P wave in Wistar rats. We performed body surface potential mapping by means of a 64-channel synchronous electrocardiotopography. The positive area covered the caudal part of the thorax, and the negative one covered the cranial part of the thorax.

Depolarization pattern of ventricular epicardium in two-kidney one-clip hypertensive rats.

The present study is the first attempt to examine the effect of left ventricular hypertrophy (LVH) on the excitation pattern of the ventricular epicardium in experimental hypertensive rats. The left renal artery was clipped in Wistar rats (n = 8; 6-8 months old; weight, 174-295 g) to produce two-kidney one-clip (2K1C) hypertension. After 4 weeks, blood pressure was measured, and epicardial potential mapping was performed under sinus rhythm from 64 unipolar electrodes regularly distributed over the ventricular epicardium.