[Mechanism of hemodynamic effects of right cardiac shunting]. / K mekhanizmu gemodinamicheskikh éffektov pravostoronnego shuntirovaniia serdtsa.

The impact of right cardiac shunting on the hemodynamic changes of the cardiovascular system was examined in acute experiments on intact dogs. The ventricular pacemaker (VP) which is a "Modul" Russian model was connected by the scheme: right ventricle-pulmonary artery. The first 20 minutes of VP operation in the complete right ventricular unloading mode resulted in increased left cardiac contraction force and rate and in elevated vascular pressure. The subsequent functioning of VP was followed by a reduction in positive inotropic effects. The changes occurring in left ventricular function and vascular tone were associated with the inclusion of mechanisms responsible for intracardiac nervous regulation to blood filling changes of the right heart due to their shunting. A fall in right ventricular pressure was perceived by myocardial mechanic receptors, by stimulating the adrenergic neurons of the intracardiac nervous system whose action is short and effected from one state to another in the transitional period.

[Role of adrenergic regulation in the genesis of myocardial ischemia]. / Rol' adrenérgicheskoi reguliatsii v geneze ishemii miokarda.

The role of altered adrenergic regulation in the development of myocardial pathology was studied in dog experiments. Activation of the sympathetico-adrenal system was induced by electrostimulation of the sympathetic tonic cardiac nerve in the first experimental series and by intravenous infusion of exogenous noradrenaline (NA) in a dose of 1 microgram/kg/min in the second series. A positive inotropic response of the heart occurred in both series. Comparison of the effect of nerve stimulation with the effect of exogenous NA showed them to be essentially different. The NA-mediator secreted in stimulation of the nerve contributed to the development of coronarogenic myocardial ischemia which was confirmed by ECG and the results of study of the coronary blood flow. Infusion of NA from an ampule in the above-mentioned doses failed to produce an effect on the alpha-receptors of the coronary vessels, but by activating the beta 2-receptors of the coronary arteries facilitated their dilatation and thus increased the blood flow in them. The functional relationship between the sympathetic tonic nerve and the alpha-adrenoreceptors of the coronary arteries and between the humoral catecholamines and their beta 2-adrenoreceptors is shown.

[Modelling of ventricular tachycardia against a background of an elongated Q-T interval]. / Modelirovanie zheludochkovoi takhikardii na fone udlinennogo intervala Q--T.

During the experiments on dogs we've created a mood of stable ventricular tachycardia induced by electrical stimulation of the left stellate ganglion at the elongated Q-T interval. The elongated cardiac systole--Q-T interval on ECG is induced by intravenous cesium chloride (l mmol/kg of dog's weight), which results in the disturbed myocardial electrolyte balance seen as tissue hypokalemia. In the dogs with electrical cardiac instability irritation of the left stellate ganglion resulted in polymorphic ventricular tachyarrhythmia in 83% of the animals. The created model has documented a role played by intracardiac pathology (electrolyte imbalance) in combination with the increased activity of the stellate ganglion in the mechanism of ventricular arrhythmia seen at the elongated Q-T interval.

[Sympathetic innervation of the heart and long Q-T syndrome]. / Simpaticheskaia innervatsiia serdtsa i sindrom udlinennogo intervala Q-T.

The effect of stimulation of the right sympathetic augmenting nerve of the heart on myocardial electrical activity and central hemodynamic values was studied in experiments on intact and stellectomized dogs. Prevailing tonus of the right augmenting nerve resulting from its stimulation was attended by ischemic changes of the myocardium and moderate lengthening of the Q-T interval in intact dogs. Increased rate of cardiac contractions and rise of arterial pressure in stellectomized dogs as well as tachycardia occurring in them due to stimulation of the nerve bore evidence of increased sensitivity of beta-adrenoreceptors in the partly denervated heart. The authors show the role of asymmetry of the sympathetic nerve regulation, caused by unilateral stimulation of the augmenting nerve, in combination with changed sensitivity of the myocardial adrenergic receptors in the development of the lengthened Q-T interval syndrome.

[Endogenous catecholamines and heart function in stimulation of the accelerator nerve]. / Endogennye katekholaminy i funktsiia serdtsa pri stimuliatsii usilivaiushchego nerva.

The role of catecholamines in realization of the effects of the augmenting cardiac nerve has been studied during acute experiments on dogs anesthesized with hexenal. Activation of pump function and myocardial contractility during nerve stimulation has been shown to be in good agreement with the increased noradrenaline concentration in the coronary sinus blood. The synthesis of adrenaline has not been found to lag behind its consumption upon the exposure described. Nerve stimulation has led to accumulation of myocardial adrenaline which takes part in realization of a positive inotropic effect to a far less extent than noradrenaline, and exerts no adverse action on cardiac function.

[Apparatus and electrodes for nerve stimulation]. / Apparat i élektrody dlia stimuliatsii nerva.

To successfully accomplish stimulation of a nerve a portable stimulator with bipolar electrodes has been designed. The level of the nerve trunk resistance was found to comprise 6 kOm. The threshold pulsed current amplitude at which the effect becomes apparent lies within the range of 1-2 mA, with the threshold of the potential pulses amplitude amounting to 4-12 V. The construction of the electrodes is described and the block diagram along with technical characteristics of the stimulator are presented.