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Biomedical subjects

V A Makarychev

Publications and source records attributed to V A Makarychev.

At least 19 recordsLinked to original sources
PubMed1991

[Preclinical ECG changes and their evaluation based on the criterion of symmetrical approach].

To reveal preclinical cardiac performance changes, conventional and unique ECG processing procedures were used in 101 individuals. A classification of heart function was developed, which was based on a comprehensive assessment of ECG. The results of the clinicofunctional classification were well comparable with those of a quantitative ECG analysis made with heuristical methods. The ratios of various ECG parameters are more informative than the absolute values of these parameters. In screening, the quantitative ECG analysis have some advantages over the visual one as it requires no thorough clinicopharmacological study. The symmetrical approach to an ECG analysis with the use of geometrical methods of simulation may be useful for the criterion assessment of preclinical alteration in cardiac performance.

Adolescent↗
PubMed1989

[Changes in electric stability and ultrastructure of the myocardium in heart rate-decreasing paired stimulation].

Experimental rabbits were subjected to a ventricular rate-decreasing paired pacing over an hour. Ventricular rates showed a 1.4-1.9-fold decrease, whereas left ventricular pressure evolution became higher, the periods of ejection and myocardial isovolumetric relation, longer, aortic diastolic pressure, lower than the baseline values. The induction thresholds of ventricular fibrillation were decreased from 16.5 +/- 1.6 mA to 7.2 +/- 3.1 mA (p less than less than 0.001). The examination of left ventricular myocardial ultrastructure indicated that the paired stimulation regimen resulted in focal contractural changes in myocardiocytes to form overcontraction zones.

Action Potentials↗
PubMed1984

Pacemaker automatism activity in atrioventricular valves and its possible role in producing cardiac arrhythmias.

In the atrioventricular valves of the hearts of 161 rabbits the authors found permanent spontaneous automatism activity. Isolated leaflets of these valves were examined with the aim to detect the electrophysiological and morphological characteristics of pacemaker formations constituting the substrate of spontaneous automatism. It was found that these formations consist of pacemaker cells of three types: P-cells, cells of intermediary type and Purkinje-type cells. Further, it was found that a decisive role in the genesis of spontaneous excitations of pacemaker cells of AV valves is played by the slow Na-Ca channel. Examination documented good innervation of the pacemaker formations, and the specific effect of mediators [acetylcholine, adrenaline, noradrenaline] on their automatism was investigated. Investigations on isolated rabbit hearts evidenced that impulses originating from the heterotopic excitation focus, localized in the AV valve leaflets, can be conducted into other compartments of the heart and can cause cardiac arrhythmias.

Acetylcholine↗
PubMed1981

[Effect of reserpine on the ultrastructure and electrical instability of the heart].

The time course of ultrastructural and electrophysiological disorders and their role in sudden death of ventricular fibrillation at various intervals of desympathization caused by reserpine administration were studied. Early in the effect of reserpine (up to 30 min), glycogen granules were found to accumulate in the sarcoplasm of cardiomyocytes. At later intervals (1-24 hours), along with glycogen accumulation destructive lesions of organoids were observed in the form of myofibrillar recontraction, destruction of mitochondria, degeneration of sarcolemma. These changes are morphologic reflections of metabolic disorders developing in the myocardium under conditions of acute desympathization of the patient, and may be one of the causes of increased vulnerability of the heart in fibrillation.

Animals↗
PubMed1979

[Change in the thresholds of development of ventricular arrhythmias after stimulation of negative emotiogenic hypothalamic centers].

The dynamics of changes in the thresholds of the origin of ventricular extrasystole, paroxysmal ventricular tachysystole and ventricular fibrillation in long-term stimulation of the ventromedial hypothalamic nucleus were studied in experiments on rabbits. It was found that myocardial resistance to the development of arrhythmias depended on the manifestation of the sympathetico-parasympathic interaction on the heart. In predominance of parasympathetic effects on the heart during hypothalamic stimulation, the threshold of the origin of arrhythmia increased by 40% for ventricular extrasystole, by 38% for paroxysmal ventricular tachysystole and by more than 36% for ventricular fibrillation. In predominance of sympathetic effects during stimulation of negative emotiogenic hypothalamic centers, the threshold of arrhythmia origin decreased by 45% for ventricular extrasystole, by 32% for paroxysmal ventricular tachysystole and by 24% for ventricular fibrillation.

Animals↗
PubMed1978

[Automatic activity of the pacemaker cells of the atrioventricular valves under the action of parasympathetic and sympathetic mediators].

Effects of neorpinephrine, epinephrine, and acetylcholine 4.5.10(-7) M--2.9.10(-6)M on the automatic activity of the pace-maker cells of the rabbit atrioventricular valves were studied. The sympathetic mediators accelerated spontaneous beating by increasing the rate of slow diastolic depolarization or by the inducing additional subthreshold potentials converted in action potentials. Acetylcholine (1.1.10(-6)M) reduced the rate of the spontaneous beating and in concentrations 2.7.10(-6)M eliminated automatic activity either by suppression of AP when subthreshold potentials gradually disappeared or by gradual decrement of AP rate and amplitude. Simultaneous application of equal doses of acetylcholine and sympathetic mediators revealed a predominant effect of acetylcholine as well as intensification of the acetylcholine effect under the influence of sympathetic mediators. Sympathetic-parasympathetic interactions can be explained by their influence on permeability of membrane of the pace-maker cells through the slow Na-Ca channel.

Acetylcholine↗
PubMed1978

[Optimal parameters for electrical auricular defibrillation].

In acute experiments on dogs the chest was opened and auricular flutter and fibrillation were induced. Current, energy and charge thresholds which eliminated this arrhythmia by the monopolar direct impulse of 1--15 ms duration were determined. The current and energy values that evoked the auricular defibrillation during direct application of the electrodes to them were minimal when the impulses of 8 ms were used: 113 +/- 13.7 mA and 10.4 +/- 2.6 mWs in elimination of the flutter, and 275 +/- 18.2 mA and 62.3 +/- +/- 9.0 mWsec in elimination of the fibrillation. The current that restored the nomotopic rhythm during direct auricular defibrillation was 50 times less than that determined during the transthoracic auricular defibrillation in dogs. The efficacy of direct auricular defibrillation indicated the necessity of the elaboration of an adequate method for its application in clinical practice.

Animals↗
PubMed1977

[Morphofunctional characteristics of pacemaker formations situated in the atrioventricular valves of the heart].

By the microelectrode technique and the method of electron microscopy multicellular formations responsible for generation of the automatic pacemaker activity were found in the cusps of the atrioventricular valves in the rabbit heart. Cells of different morphological structure were revealed: P-cells, cells of the Purkinje type and transitional cells. These formations have rich innervation, mainly of cholinergic nature. A certain correlation was established between the morphological and electrophysiological characteristics of these cells.

Animals↗
PubMed1976

[Automatic activity of pacemaker cells in the atrioventricular valves of the rabbit heart].

The microelectrode technique applied revealed an automatic activity of the pacemaker cells with slow diastolic depolarization in the cusps of the atrioventricular valves obtained from 34 rabbit hearts. Electrophysiological characteristics of the action potentials of these cells were investigated. Inhibitors of slow sodium-calcium canal (Mn++, Co++, and Mg++ ions) proved to eliminate the automatic activity of the pacemaker cells. When the content of potassium ions was elevated in the perfusion solution, no suppression occurred. It is suggested that the automatic activity of the pacemaker cells in the atrioventricular values depended mainly on the functioning of the slow sodium-calcium canal.

Action Potentials↗
PubMed1975

Genesis of arrhythmias and mechanism of electrical defibrillation of the heart.

Atrial arrhythmias were induced in experiments on dogs by electrical stimulation or by local application of aconitine and methacholine to the atrium. The action of the defibrillator discharge on these arrhythmias was studied. The defibrillator discharge abolished the arrhythmias maintained by the circus movement of the excitation wave over the atria but did not abolish sinus tachycardia or ectopic aconitine tachysystoles. The threshold of the defibrillating effect depends on the existence of micro-or macro-reentries. Thmechanism of defibrillation consists of excitation of the atrial myocardium with a consequent decrease in the pathway for the circulation of excitation to below the critical size for maintaining the circus movement of the excitation wave. The axtion of the defibrillator does not inihibit the automatism of the nomotopic and heterotopic cardiac pacemakers.

Aconitum↗