Seasonal changes of electrophysiological heterogeneities in the rainbow trout ventricular myocardium.

Introduction: Thermal adaptation in fish is accompanied by morphological and electrophysiological changes in the myocardium. Little is known regarding seasonal changes of spatiotemporal organization of ventricular excitation and repolarization processes. We aimed to evaluate transmural and apicobasal heterogeneity of depolarization and repolarization characteristics in the rainbow trout in-situ ventricular myocardium in summer and winter conditions.

Stretch-excitation correlation in the toad heart.

The activation sequence of the ventricular myocardium in ectotherms is a matter of debate. We studied the correlation between the ventricular activation sequence and the pattern of local stretches in 13 toads (). Epicardial potential mapping was done with a 56-lead sock array.

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.

Load-induced changes in ventricular repolarization: evidence of autonomic modulation.

Augmented hemodynamic load increases the risk of arrhythmogenesis by modulating cardiac repolarization duration. We hypothesized that the intervention on the autonomic tone may affect the load-dependent changes in ventricular repolarization. Activation-recovery intervals were measured in unipolar electrograms simultaneously recorded from 64 ventricular epicardial leads, in a total of 26 chinchilla rabbits in resting conditions, and after 1 and 10 min of aortic stenosis.

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.

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.

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.

Physics and mechanism of ultrasonic impact.

More and more experts and researchers in industry express their interest in the application of deformation effects of various peening techniques on the metal surface. This is primarily due to a relatively simple directional change in condition at the surface and in sub-surface layers of the material as a result of plastic deformation due to impulses of force caused, among other things, by converting ultrasonic oscillations of various impacting elements (indenters) at the treated surface. These effects are of a stochastic nature and their duration (or the time of impact) is generally measured in units of microseconds.