Biomedical subjects
Publications and source records attributed to V E Tolpekin.
The authors propose a design of an axial shovel pump for extracorporeal circulation. They show how to introduce it into various cardiovascular segments and make a comparative assessment of its efficacy in relation to the type and severity of heart failure, surgical access, and treatment policy.
Intraventricular blood-forcing-principle-based pneumo- and hydraulic assistance circulation device test results are proposed. The system consists of a uninipple valveless dome pump, a pneumo- or hydraulic drive, and an artificial pericardium. Stand tests of these systems and medical-biologic experiments on dogs and 17 calves were performed. The duration of these experiments was up to several days. In this report, the features of surgical techniques, perfusion parameters, control principles, hemodynamic variations, complications, and other problems concerning realization of the proposed method are discussed.
Thirty experiments were conducted on calves for hemodynamic study of mechanical aid to the heart (biventricular bypass by two artificial ++"Module"+ ventricles of the heart) in acute cardiac failure. The cavities of the heart were cannulated with a special perforating device which, when necessary, is an obturator of the main line. Analysis of the hemodynamic values showed a sufficiently high efficacy of biventricular shunting in acute cardiac failure. The device for draining the heart cavities has advantages over the traditional main lines, in particular the number of complications from bleeding and air embolism reduces with its use.
Experiments were performed on 15 mongrel dogs to evaluate the influence of electrostimulated contractions of the hind limb and abdominal skeletal muscles on the efficacy of assisted circulation (AC). The influence of massage of the abdomen on AC efficacy was studied in 10 experiments. In electrostimulation of the hind limb muscles the drainage along the femoral vein, measured by the direct method, increased threefold: from 58 +/- 9 to 162 +/- 7 ml/min under conditions of an intact heart and from 5.8 +/- 0.8 to 15 +/- 1.2 ml/min in cardiac insufficiency. The efficacy of AC by the method of left-ventricular bypass by means of the Module artificial heart ventricle (AHV) increased through the flow of blood to the heart, which was manifested by greater AHV performance with rise of systolic and diastolic pressure to 7-8 mm Hg. In cardiovascular insufficiency the influence of electrostimulation on AC efficacy was weaker, the systolic and diastolic pressure increased only by 2-4 mm Hg, in massage of the abdomen both indices increased by 8-10 mm Hg.
The article discusses the results of applying for the first time Soviet-made "Modul" and "Yasen" artificial ventricles of the heart (AVH) in a left ventricular bypass regimen in patients with refractory cardiac insufficiency. Improvement of AVH design and rational tactics of attendant drug therapy allowed the period of the safe application of the AVH in the organism to be increased to more than 8 days.
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Two series of experiments were conducted to assess the potential of artificial ventricular bypass in restoring cardiac activity. One series evaluated use of a paracorporeal left ventricle in 17 calves; the other evaluated biventricular bypass in 11 calves. Module pumps with a seamless blood chamber of polyurethane were used. Pump function and system parameters were controlled by a Sinus VK-2 control system. Assisted perfusion began with the induction of ventricular fibrillation. The experiments showed that left ventricular bypass was an effective method for long-term maintenance of the hemodynamics during fibrillation, leading to certain biochemical corrections and restored electrical activity and myocardial contractile function. The hemodynamic state was maintained at a higher level with biventricular bypass and was accompanied by a greater percentage of restored myocardial function. Uneven restoration of contractile activity in the left and right ventricles points to the need for adequate support of both ventricles.
The development of autonomous systems for the artificial heart (AH) and for circulatory assistance (CA) has taken several directions. Studies relating to one direction--the development of paracorporeal and implanted systems based on thermal or electric motors--have been conducted at our institute in two stages, moving from stationary systems to totally implanted systems for long-term use. The development of these systems is described. Improvements in the linear solenoid motor, used in some of the first paracorporeal systems, enabled progress toward the development of implanted CA systems based on a reversing electrohydraulic actuator. Modifications were also made in the control system. Early animal testing of these systems indicated that they could be effective in unburdening the heart cavities during left and right bypasses. Full implantation, however, demanded that the devices have improved forms and dimensions and less weight. Smaller electromechanical systems are being developed, and we are experimenting with ways to increase the overall autonomy of the system. An orthotopic model of an implanted AH is promising. Experiments continue on the use of the body's own skeletal muscles to create a blood pump.
The efficiency of electric defibrillation of the heart was assessed in 17 experiments where the position of action electrodes varied. It is suggested that intravascular application of one electrode plus extravascular application of the other gives the optimum effect. The duration of unassisted reversible fibrillation averaged 3 minutes.
A comparative study of two methods of bypassing the heart with artificial ventricles (AV) was conducted: left atrium-aorta and left ventricle-aorta. The following factors permit left ventricular bypass to compete successfully with left ventricle-aorta bypass: creation of perfected pumps with low input impedance, use of materials with high resistance to thrombus formation for preparation of the AV and main connecting lines, and development of optimum methods of anticoagulant, disaggregation, and cardiac therapy so that there is no danger of thrombosis and hemorrhage, either experimentally or clinically. Thrombosis was the primary cause of death in only one case in a series of experiments on 15 calves with AV connected according to the atrium-aorta scheme. The positive changes in hemodynamics were approximately the same with the two methods.
Intra-aortic counterpulsation with a balloon pump (IABP) was used in 63 patients with cardiogenic shock, heart failure after surgery with artificial circulation, internal lacerations of the myocardium, or unstable angina. It was found that the IABP was most efficient in conditions related to myocardial ischemia. Use of arteriovenous perfusion (in 11 patients) or artificial ventricles is indicated in severe perturbations of the pumping function of the heart. As experience has shown, cardiologic and heart surgery patients usually have multiorgan insufficiency. For this reason, it is necessary to use other artificial organs in complex treatment: artificial lungs, kidneys, livers, etc.
Assisted circulation is now used in the treatment of severe forms of heart failure which complicate the course of many diseases. Application of one method of assisted circulation--intra-aortic counterpulsation by a balloon pump in cardiogenic shock--was successful: prolonged survival (over 1 year) was obtained in 18% of the patients. A further decrease in the mortality rate is dependent on the rational organization of treatment for these patients. This poses two major problems: the organization of treatment of patients in cardiogenic shock and postoperative heart failure in large cardiologic and heart surgery centers, and treatment of heart failure in patients in whom it has occurred secondarily. We developed a method of organizing the treatment of these patients beginning in the prehospital stage and continuing in a specialized hospital. In addition to methods of assisted circulation, various intensive care methods and hemosorption (in poisoning by liver toxins), hemodialysis (in anuria), etc., are used. Although this type of organization complicates therapy, the results are significantly improved.
The paper sums up experience with the development of a domestic system for auxiliary circulation and a module-type artificial ventricle, and presents the results of their experimental trial and first-ever clinical use in patients with severe heart failure following open-heart surgery. Good operational characteristics and high efficiency of this equipment in clinical as well as experimental terms are demonstrated.
A method is suggested of evaluating the cardiac internal hydraulic resistance R0 and maximal blood flow at zero post load Q0. R0 in intact dogs is 11.9 mm/Hg/l/min and Q0 is 27.1 l/min. In the condition of acute cardiac insufficiency and under the effect of large adrenaline doses these parameters were, respectively, 8.8 mm Hg/l/min, 7.0 mm Hg/l/min and 36.9 l/min, 38.8 l/min. The reducing of of R0 reflect the reduction of rigidity of the myocardial wall, and the increase of Q0 reflects the increase of the cardiac muscle inotropism connected with the compensatory increase of the catecholamines level in blood.
Trauma inflicted to blood in different method of assisted circulation was studied in experiments and in the clinic. Morphological disturbances of red blood cells and changes in their aggregation properties were revealed. Left ventricular shunt and aorto-aortic counter-pulsation are attended with increased aggregation properties of blood platelets. Aorta-aortic counter-pulsation causes a greater damaging effect than shunting of the left ventricle. Counter-pulsation by means of a balloon pump is attended with least hemolysis.
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Experiments were conducted on dogs; a study was made of the influence of a method of assisted circulation--contrapulsation, on the myocardial ultrastructure. A sharp glycogen accumulation in the muscle cells of the heart, the presence of mitochondria with a marked osmophilic microgranular matrix, and also a high pinocytic activity of the capillary endothelial cells were revealed by electron microscopy. The data obtained pointed to the metabolic reconstruction in the myocardium, and primarily to the reduction of the energy level of the myocardial muscle cell function. The changes in the myocardial ultrastructure revealed apparently provided the positive therapeutic effect.