Biomedical subjects
Publications and source records attributed to V I Shumakov.
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.
Non-traditional methods of treatment of diabetes and its complications are discussed, including transplantation of the pancreas and the pancreatic islet-cell cultures, application of the artificial endocrine pancreas device and insulin-dosing apparatus, hemosorption, hemodialysis, and kidney transplantation. The pancreas transplantation is the procedure allowing to completely withhold exogenous insulin injections but which should be performed in specialized transplantation centres due to its complexity. Demonstrated is the long-term positive effect of the pancreatic islet-cell culture transplantation on the course and late complications of diabetes. The specific features and prospects of automated insulin administration by electromechanical devices in diabetes management are discussed. Noted is the positive effect of hemosorption on different diabetes manifestations, which is most pronounced in insulin-resistant cases associated with high anti-insulin antibody titres. The described methodologies require further improvement and may be used both as independent procedures and as valuable aids in traditional management of diabetes.
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The U.S.S.R. and United States have cooperated on artificial heart research and development since 1974. The exchange of information and developmental models of the artificial heart continued in the years 1981-1984. Soviet and American scientists also continued to meet regularly on specific projects relating to a variety of activities, including the testing of different heart models and biomaterials and experiments with implantation. Three symposia have been held to share research results and identify additional research problems. Joint collaboration has been both expedient and effective and has accelerated research in this area.
Experiments with the Poisk model of an ellipsoid artificial heart are reported. With a modified model of the diaphragm type made from polyurethane, calves survived for a mean of 55 days, with a maximum survival of 3 months. With adequate anticoagulation therapy, no thrombogenesis was observed in the blood chamber (except for the inlet valves); a low level of plasma hemolysis was observed postoperatively. Good correlation was demonstrated between the stroke volume and left and right atrial pressures. Changes in the blood coagulation indices are reported. Implantation of a clinical variant of this prosthesis into human cadavers demonstrated no difficulties in placing the heart in the pericardial cavity. Developmental efforts are continuing.
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.
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In valve replacement operations on 78 patients with acquired heart disease, the efficiency of phosphocreatine in intraoperative protection of ischemic myocardium was evaluated by clinical, morphologic, and biochemical methods. Phosphocreatine (8 to 10 mmol/L) in a blood cardioplegic solution was used in operations on 41 patients; in the control group (37 patients) standard blood cardioplegia was used. In the group with phosphocreatine treatment we observed more rapid recovery of hemodynamics after release of the aortic cross-clamp, a decreased frequency of fibrillation, and more frequent restoration of sinus rhythm even if there were sinus rhythm disturbances before aortic cross-clamping. Analysis of the biopsy samples taken from the right ventricle showed protection of the sarcolemma against ischemic damage afforded by phosphocreatine and complete preservation of high-energy phosphates. The results obtained confirm the conclusion made by Robinson, Braimbridge, and Hearse (J Thorac Cardiovasc Surg 1984; 87:190-200) that phosphocreatine is an effective additional cardioprotective agent when used in cardioplegic solutions.
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In 144 experiments carried out on dogs, the possibility was proved to use for the recipient's protection during transplantation either deep immersion hypothermia or total artificial circulation without it being filled with the donor's blood. In order to maintain cardiac activity after clinical death of a non-heparinized organism for the purpose of later heart transplantation the authors propose to use the direct mechanical cardiac massage (DMCM) which makes possible not only to restore adequate pulsating blood flow in the dead body but also to assess after restoration of the heart's pump function the suitability of using it for transplantation. Functional adaptation of a transplanted heart proceeds in 3 stages: pronounced heart failure (5-15 min), functional heart failure (4-6 hours), stabilization of cardiac activity (2-3 days). Implantation of a second heart in experimental left ventricular failure of the recipient helped to achieve an effective and prolonged reduction of excessive functional overload of the affected heart.
Increasing sensitivity to drugs, elimination of endotoxicosis, recovery of normal homeostatic control after hemocarboperfusion help to break off the vicious circles associated with severe cardiovascular disorders, and improve the effect of subsequent medication. Hemocarboperfusion added to combined intensive care and resuscitation procedures was associated with a 82.9% success rate.
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An atomic artificial heart for orthotopic implantation was developed with the following characteristics: volume, 1.2 L; weight, 1.5 kg; radioisotope power, 45 W; operating life, up to 5 years; hemodynamics, similar to natural hemodynamics. The artificial heart includes a thermal drive with systems for regulating power, feeding steam into the cylinders, return of the condensate to the steam generator, and delivery of power to the ventricles and heat container. The artificial heart is placed in an artificial pericardium partially filled with physiologic solution. It uses a steam engine with two operating cylinders that separately drive the left and right ventricles. There is no electronic control system in the proposed design. The operation of the heat engine is controlled, with preservation of autoregulation by the vascular system of the body. The separate drives for the ventricles is of primary importance as it provides for operation of the artificial heart through control of cardiac activity by venous return. Experimental testing on a hydromechanical bench demonstrated effective autoregulation.
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