Correlation in time of the process of cardiac ventricle intramural depolarization and of distribution of cardioelectric field potentials of the dog <Emphasis Type="Italic">Canis famjliaris</Emphasis>

Based on a multichannel synchronous mapping of heart electric potentials, the sequence in time of the ventricle myocardium depolarization was compared with dynamics of distribution of cardioelectric potentials on the dog body surface. The cardioelectric field on the dog body surface at the period of the initial ventricular activity has been shown to be characterized by the presence of two inversions of the mutual disposition of areas of positive and negative potentials. Contribution to formation of distribution of the cardioelectric potentials on the body surface at each moment of the period of initial ventricular activity was made by all myocardial layers involved in excitation.     

Cardiac electric field at the period of depolarization and repolarization of the frog heart ventricle

Multichannel mapping of electrical field on heart ventricle epicardium and the body surface in frogs Rana esculenta and Rana temporaria was performed at periods of the ventricular myocardium depolarization and repolarization. The zone of the epicardium early depolarization is located on epicardium of the ventricle base posterior wall, while the late depolarization zone--on its apex and on the base anterior wall. The total vector of sequence of the ventricle epicardium depolarization is directed from the base to the apex. The zone of the early repolarization is located in the apical area, while that of the late one--in the area of the base. On the frog body surface the cardioelectric field with the cranial zone of negative and the caudal zone of positive potentials is formed before the appearance of the QRS complex on ECG. At the period of the heart ventricle repolarization the zone of the cardioelectric field negative potentials is located in the cranial, while that of the positive ones--in the body surface caudal parts. The cardioelectric field on the frog body surface at the periods of depolarization and repolarization of the ventricle myocardium reflects adequately the projection of sequence of involvement with excitation and of distribution of potentials on epicardium.     

Cardiac electric field at the period of depolarization and repolarization of the frog heart ventricle

Multichannel mapping of electrical field on heart ventricle epicardium and the body surface in frogs Rana esculenta and Rana temporaria was performed at periods of the ventricular myocardium depolarization and repolarization. The zone of the epicardium early depolarization is located on epicardium of the ventricle base posterior wall, while the late depolarization zone—on its apex and on the base anterior wall. The total vector of sequence of the ventricle epicardium depolarization is directed from the base to the apex. The zone of the early repolarization is located in the apical area, while that of the late one—in the area of the base. On the frog body surface the cardioelectric field with the cranial zone of negative and the caudal zone of positive potentials is formed before the appearance of the QRS complex on ECG. At the period of the heart ventricle repolarization the zone of the cardioelectric field negative potentials is located in the cranial, while that of the positive ones—in the body surface caudal parts. The cardioelectric field on the frog body surface at the periods of depolarization and repolarization of the ventricle myocardium reflects adequately the projection of sequence of involvement with excitation and of distribution of potentials on epicardium.     

Formation of Cardioelectric Field on the Body Surface at a Period of Activation of Ventricular Myocardium in the Chicken Gallus domesticus

Spatial and temporal non-uniform and polyfocal depolarization of the subendocardial, intramural, and subepicardial layers of the ventricle myocardium in the chicken have been established experimentally. Different depth and time of formation of activation centers in the ventricular myocardium provide the appearance of groups of multiple depolarization foci on the epicardial surface of the ventricles. During the initial ventricular activity the cardioelectric field (CEF) on the chicken body surface is characterized by three periods of the dynamics of distribution of potentials: (1) the period of their gradual changes reflecting the electrical activity of excitation foci in the subendocardial, intramural, and subepicardial ventricular layers of myocardium on CEF; (2) the period of inversion consisting of an alteration of the mutual arrangement of the positive and negative CEF areas, this alteration corresponding in time to polyfocal depolarization of the epicardial surface of the ventricles; (3) the period of stability, during which the arrangement of the positive and negative CEF regions does not change, which is due to depolarization of multiple myocardium zones at the final phase of the heart ventricle activation.     

Cardiac electric field on the epicardial and body surfaces during the period of depolarization and repolarization of ventricular myocardium in pikes

Body surface and ventricular epicardial potential distributions during the electrocardiographic QRST interval were studied in pikes with the aid of potential mapping. The earliest epicardial activation was observed at the posterior base near the atrioventricular orifice. The areas of the earliest repolarization were found at the apex and the posterior base, whereas the area of the latest repolarization was detected at the anterior base. In the initial period of the QRS, the minimum was developed in the middle third of the right lateral body surface, and the maximum in the middle third of the ventral body surface. The body surface potential distribution during the ST-Twas characterized by the clear-cut negative potential zone in the cranial ventral area with the rest of the body surface having positive potentials, a pattern being largely unchanged throughout the period of the T-wave. The ventricular epicardial repolarization sequence differed from the activation sequence. The ventricular epicardial depolarization and repolarization sequences as well as epicardial potential distributions are expressed in the cardiac electric field on the body surface during the QRS and ST-T complexes.     

A cardiac electric field on the body surface in rats with left ventricular hypertrophy caused by experimental renovascular hypertension

The dynamics of potential distribution of cardiac electric field on the body surface was studied in renovascular hypertensive rats (Goldblatt type) during the ventricular activity. Three inversions of the mutual location of positive and negative areas of the cardiac electric field on the body surface were found in normotensive and hypertensive rats during the QRS-T period. Left ventricular hypertrophy of the heart in rats caused by renovascular hypertension results in changes of temporal and amplitude characteristics of the body surface potential distribution during the initial and terminal ventricular activity. The shifting trajectory of the positive and negative areas and their extremal ranges on the body surface does not change during the ventricular activity in rats with left ventricular hypertrophy of the heart as compared to the initial normotensive state.     

Cardioelectric field on the atrial surface in pigs

The form and distribution of extracellular cardioelectric potentials and the sequence of the excitation wave propagation on epicardium of the pig atria were studied by the method of multichannel synchronous cardioelectrotopography. The studies have shown that in pig the excitation wave breaks on epicardium of the right atrium at the base of the upper vena cava. Negative initial atrial complexes are registered in this area. Two fronts of excitation wave spread from the zone of initial epicardial activation: one--to upper segments of dorsal and ventral sides of the right atrium, the second--to inter-atrial septum. The excitation wave comes to the left atrium with a delay relative to the beginning of depolarization of the right atrium. On account of the successive movement of the front of the excitation wave from pacemaker the two-phase potentials are formed on greater part of the epicardium of the pig atria. The lower part of the auricle of the left atrium is depolarized in atrial epicardium in the last turn. The sequence of excitation wave propagation in atrial epicardium close to ravenous (dog) and ungulate (sheep) animals and man is typical for the pig, but herewith the differences in time of covering the atria with excitation do exist.     

Spatiotemporal characteristics of the heart electrical field in the period of ventricular depolarization in athletes training endurance and strength

As a result of hemodynamic and structural changes occurring in the heart of athletes under the influence of systematic physical loads, the myocardial electrical activity changes, which is reflected on the electric field formed on the body surface. The electrical activity of the heart during ventricular depolarization at rest was studied in the highly skilled athletes training to develop physical characteristics (endurance and strength) by the method of electrocardiotopography. The studied athletes had similar patterns of movement of zones of positive and negative cardiac electrical potentials and location of extrema as well as the total depolarization duration but showed significant distinctions in (1) the amplitude of the maximum negative extremum; (2) the time of the beginning and end of the first inversion; (3) the duration of the second inversion, the initial stage, and the stability period between inversions; and (4) the relative position of positive and negative cardiopotential zones.     

Cardioelectric Field on the Bird Body Surface during Activation of Atrial Myocardium

Cardioelectric field (CEF) on the body surface of birds (hen and pigeon) at the period of atrial excitation was studied by the method of the 64-channel synchronous electrocardiotopography. At the period of the atrial depolarization in the birds the zone of CEF negative potentials on the body surface is located cranially with respect to the zone of positive potentials. At the initial moments of P wave the minimum is located in the cranial (hen) or middle (pigeon) third of the dorsal body surface, while the maximum—in the area of the heart projection onto the ventral (hen) or left-lateral (pigeon) body surface. The maximum and minimum of the potential reach the greatest value at the period of the middle part of the P wave (near the peak), their amplitude being higher in pigeons. The distribution dynamics of the CEF potentials on the body surface is similar in different bird species and is characterized by stability in mutual disposition of positive and negative zones. The interspecies and intraspecies CEF variability on the body surface at the period of the atrial activation seems to be due to differences in the heart disposition in the chest. At the period of the atrial myocardium activation, CEF on the bird body surface reflects adequately projection of the potential distribution on epicardium and the sequence of spreading of excitation in the atrial myocardium, including that in the presence of several fronts of depolarization waves.     

Time correlation of the cardiac electric field on the body surface and depolarization sequences in the pigeon heart ventricle epicardium

Multifocal depolarisation of the pigeon ventricle's epicardium was revealed. A time inversion correlation was found between cardiac electrical field's positive and negative areas on the body surface and the multifocal depolarisation of the ventricle epicardium, during the period of initial ventricular activity.     

The electrical resistance of the lungs,intercostal muscles,and kidneys in hypertensive ISIAH rats

A comparative study of the bioelectrical impedance of normotensive and hypertensive animal tissues was carried out. It was found that the electrical resistance of kidneys, lungs, and intercostal muscles in rats with arterial hypertension (ISIAH strain) was significantly lower than in normotensive Wistar rats, which indicates that the volume of circulating blood and the total amount of fluid were increased in animals with arterial hypertension. The fact that the resistance of the conducting medium is decreased in arterial hypertension should be taken into account in the analysis of cardioelectric potentials on the body surface and electrocardiograms in conventional leads, as well as for the purposes of the development of heterogeneous torso models and for verification of recovery algorithms for electrical properties of chest tissues.     

Sequence of ventricular repolarization under body cooling in the frog

Lowering the temperature is known to prolong the repolarization of cardiomyocytes. However, whether the prolongation of action potentials is uniform throughout the myocardium, and whether this prolongation is obvious in ECG, remains unclear. Ventricular repolarization sequences and body surface potential distributions were studied in 20 frogs Rana temporaria using epicardial and body surface potential mapping. An apex-to-base ventricular repolarization sequence corresponded to the distribution of local repolarization durations was demonstrated at the temperature of 18 degrees C. The body surface potential distribution during the ST-T complex was characterized by the cranial negative and caudal positive potential areas. Under the body cooling to 10 degrees C, repolarization prolonged to a greater extent at the apex that resulted in the base-to-apex repolarization sequence, which, in turn, caused an inversion in the body surface potential distribution with cranial portion of the body being positive and caudal portion being negative.     

Noninvasive electrocardiographic imaging for cardiac electrophysiology and arrhythmia

Over 7 million people worldwide die annually from erratic heart rhythms (cardiac arrhythmias), and many more are disabled. Yet there is no imaging modality to identify patients at risk, provide accurate diagnosis and guide therapy. Standard diagnostic techniques such as the electrocardiogram (ECG) provide only low-resolution projections of cardiac electrical activity on the body surface. Here we demonstrate the successful application in humans of a new imaging modality called electrocardiographic imaging (ECGI), which noninvasively images cardiac electrical activity in the heart. In ECGI, a multielectrode vest records 224 body-surface electrocardiograms; electrical potentials, electrograms and isochrones are then reconstructed on the heart's surface using geometrical information from computed tomography (CT) and a mathematical algorithm. We provide examples of ECGI application during atrial and ventricular activation and ventricular repolarization in (i) normal heart (ii) heart with a conduction disorder (right bundle branch block) (iii) focal activation initiated by right or left ventricular pacing, and (iv) atrial flutter.     

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. A transmural gradient in repolarization durations in frogs (Endo>Epi, P<0.024) corresponds to the gradient in repolarization times. No significant transmural difference in repolarization duration is observed in pike that produces a repolarization sequence from Endo to Epi (Endo相似文献   

Dynamics of intramural scroll waves in three-dimensional continuous myocardium with rotational anisotropy.

It has been suggested that reentrant activity in three-dimensional cardiac muscle may be organized as a scroll wave rotating around a singularity line called the filament. Experimental studies indicate that filaments are often concealed inside the ventricular wall and consequently, scroll waves do not manifest reentrant activity on the surface. Here we analyse how such concealed scroll waves are affected by a twisted anisotropy resulting from rotation of layers of muscle fibers inside the ventricular wall. We used a computer model of a ventricular slab (15x15x15 mm(3)) with a fiber twist of 120 degrees from endocardium to epicardium. The action potential was simulated using FitzHugh-Nagumo equations. Scroll waves with rectilinear filaments were initiated at various depths of the slab and at different angles with respect to fiber orientation. The analysis shows that independent of initial conditions, after a certain transitional period, the filament aligns with the local fiber orientation. The alignment of the filament is determined by the directional variations in cell coupling due to fiber rotation and by boundary conditions. Our findings provide a mechanistic explanation for the prevalence of intramural reentry over transmural reentry during polymorphic ventricular tachycardia and fibrillation.     

Responses of units in the magnocellular part of the medial geniculate body to acoustic and somatosensory stimulation

Responses of 150 neurons in the magnocellular part of the medial geniculate body to clicks and to electrodermal stimulation of the contralateral forelimb were investigated in cats immobilized with myorelaxin. Of the total number of neurons 65% were bimodal, 16.6% responded only to clicks, and 15.4% only to electrodermal stimulation. The unitary responses were excitatory (spike potentials) and inhibitory (inhibition of spontaneous activity). Responses beginning with excitation occurred more frequently to stimulation by clicks than to electrodermal stimulation, whereas initial inhibition occurred more often to electrodermal stimulation. The latent period of the initial spike potentials in response to clicks and to electrodermal stimulation was 5–27 and 6–33 (mean 11.6 and 16.2) msec respectively. Positive correlation was found between the latent periods of spike potentials recorded in the same neurons in response to clicks and to electrodermal stimulation, and also to electrodermal stimulation and to stimulation of the dorsal funiculus of the spinal cord. It is concluded that the magnocellular division of the medial genicculate body is a transitional structure between the posterior ventral nucleus and the parvocellular division of the medial geniculate body, and that in addition, it is connected more closely with the auditory than with the somatosensory system. It is suggested that the somatosensory input into the magnocellular division of the medial geniculate body is formed mainly by fibers of the medial lemniscus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 2, pp. 133–141, March–April, 1978.     

The Hemodynamic Response of the Right Ventricle Following Acute and Chronic Partial Obstruction of the Main Pulmonary Artery in Dogs

In eight adult dogs the main pulmonary artery was constricted to elevate the right ventricular peak systolic pressure to 50% of the peak aortic pressure at rest. The response of the right ventricle was assessed immediately, at 30 minutes and at six months. The right ventricle responded to acute systolic loading by complete compensation. After 30 minutes there was a reduction in the right ventricular outflow tract resistance. The cardiac output, heart rate and aortic pressure were maintained. The right ventricular systolic ejection period, end-diastolic pressure, peak pressure time, mean systolic pressure, right ventricular—main pulmonary artery mean systolic gradient, right ventricular work index, systolic work and outflow tract resistance were all increased.The right ventricle in the dog was shown to have an immediate capacity to compensate for systolic loading and retains this capacity for long periods of time. The ability to increase work is accomplished by adaptations in right ventricular physiology which increase right ventricular mean systolic pressures and prolong the right ventricular ejection period.     

Uniform Action Potential Repolarization within the Sarcolemma of In Situ Ventricular Cardiomyocytes

Previous studies have speculated, based on indirect evidence, that the action potential at the transverse (t)-tubules is longer than at the surface membrane in mammalian ventricular cardiomyocytes. To date, no technique has enabled recording of electrical activity selectively at the t-tubules to directly examine this hypothesis. We used confocal line-scan imaging in conjunction with the fast response voltage-sensitive dyes ANNINE-6 and ANNINE-6plus to resolve action potential-related changes in fractional dye fluorescence (ΔF/F) at the t-tubule and surface membranes of in situ mouse ventricular cardiomyocytes. Peak ΔF/F during action potential phase 0 depolarization averaged −21% for both dyes. The shape and time course of optical action potentials measured with the water-soluble ANNINE-6plus were indistinguishable from those of action potentials recorded with intracellular microelectrodes in the absence of the dye. In contrast, optical action potentials measured with the water-insoluble ANNINE-6 were significantly prolonged compared to the electrical recordings obtained from dye-free hearts, suggesting electrophysiological effects of ANNINE-6 and/or its solvents. With either dye, the kinetics of action potential-dependent changes in ΔF/F during repolarization were found to be similar at the t-tubular and surface membranes. This study provides what to our knowledge are the first direct measurements of t-tubule electrical activity in ventricular cardiomyocytes, which support the concept that action potential duration is uniform throughout the sarcolemma of individual cells.     

Reflection of distribution of the epicardial ventricular potential on the dog body surface during electrical stimulation of the myocardium]

Electrical pacing of the apex, base, and free wall of the heart right and left ventricles, as well as the left ventricle's interventricular septum revealed that localisation of the ectopic focus determined the sequence of ventricular depolarisation, the site formation, and the pathway of displacement of the areas' positive and negative potentials and their extrema on the thoracic surface. Time of the mutual movement (inversion) of positive and negative zones on the body surface was found to depend on the pacing site in the wall of ventricles.     

Immunohistochemical demonstration of serotonergic and peptidergic nerve fibers in the subcommissural organ of the dog

Summary The distributional patterns of serotonin-, luteinizing hormone-releasing hormone (LHRH)-, oxytocin (OXT)- and vasopressin (VP)-immunoreactive nerve fibers were studied in the subcommissural organ (SCO) of the dog by use of the peroxidase-antiperoxidase technique.Abundant serotonergic and moderate numbers of peptidergic nerve fibers running toward the ventricular surface were observed among the cylindrical ependymal cells in the SCO of the dog. Concerning the distributional density of the peptidergic nerve fibers, VP-immunoreactive fibers displayed the highest and LHRH-immunoreactive fibers the lowest values. Most serotonergic and peptidergic fibers returned to the basal portion of the SCO after forming loops immediately beneath the ventricular surface of the ependymal layer. Serotonin-immunoreactive fibers often established a perivascular plexus around the blood vessels in the SCO.At the electron-microscopic level, after use of antiserum to serotonin dark immunoprecipitate was observed in large granular vesicles and the matrix surrounding small and large, clear vesicles and mitochondria; VP immunoreactivity was localized in the large granular vesicles.Serotonergic nerve fibers could be detected in the SCO of the newborn dog. Although the distributional density was in principle not different from that in the adult animal, individual fibers showed immature features such as growth cones and insufficiently swollen varicosities. After penetrating into the ventricle, in the newborn dog, a few serotonin-immunoreactive fibers ran for a relatively long distance on the ependymal surface.