Histopathology Image Analysis in Two Long-Term Animal Experiments with Helical Flow Total Artificial Heart.

Histopathological analysis can provide important information in long-term experiments with total artificial heart (TAH). Recently, a new type of blood pump, the helical flow total artificial heart (HF-TAH) was developed. This study aimed to investigate the changes in selected vital organs in animal experiments with implanted HF-TAH. Samples from lung, liver, and kidneys from two female goats (No. 1301 and No. 1304) with implanted HF-TAH were analyzed. Tissue samples were fixed in 10% formaldehyde and 4 µm thick transverse sections were stained with hematoxylin-eosin (HE). Additional staining was done for detection of connective tissue (Masson-Goldner stain) and for detection of iron (hemosiderin) deposits (Perls stain). Sections were scanned at 100× and 500× magnification with a light microscope. Experiment no. 1301 survived 100 days (cause of termination was heavy damage of the right pump); experimental goat no.1304 survived 68 days and was sacrificed due to severe right hydrodynamic bearing malfunction. Histopathological analysis of liver samples proved signs of chronic venostasis with limited focal necrotic zones. Dilated tubules, proteinaceous material in tubular lumen, and hemosiderin deposits were detected in kidney samples. Contamination of the organs by embolized micro-particles was suspected at the autopsy after discovery of visible damage (scratches) of the pump impeller surface (made from titanium alloy) in both experiments. Sporadic deposits of foreign micro-particles (presumably titanium) were observed in most of the analyzed parenchymal organs. However, the described deposits were not in direct connection with inflammatory reactions in the analyzed tissues. Histopathological analysis showed the presence of minimal contamination of the lung, kidney, and liver tissue samples by foreign material (titanium very likely). The analysis showed only limited pathological changes, especially in liver and kidneys, which might be attributed to the influence of artificial perfusion often observed in chronic TAH experiments.

Acute and chronic consequences of non-pulsatile blood flow pattern in long-term total artificial heart experiment.

Vessel pulsation is presumably a key physiological function for the optimal supply of peripheral tissues and vital organs by oxygen and nutrients. The absence of pulsatility might impair the peripheral perfusion stability and trigger microvascular dysfunction of vital organs. The main purpose of this study was to investigate the influence of non-pulsatile flow on the microcirculation in experimental goat with implanted undulation pump total artificial heart (UPTAH). A microscopic system (Keyence, Japan) for the direct observation of the microcirculation of bulbar conjunctiva was used. Following the acute flow pattern change (from pulsatile to non-pulsatile one), the number of perfused capillaries decreased significantly (from 34.7+/-6.3 to 19.7+/-4.1 number of capillaries/mm; P<0.05). The velocity of erythrocytes dropped (from 526+/-83 to 132+/-41mum/s; P<0.05). The velocity of erythrocytes and capillary density were only partly recovered, when the pulsatile flow mode was restored. Histopathological analysis after 33 days of pumping in non-pulsatile mode revealed the presence of chronic venostasis, tissue edema, hemorrhages, hypoxia and ischemic necroses in the tissue samples from liver, kidneys and lung. These findings could be regarded as a direct effect of the chronic non-pulsatile pumping mode and inadequate blood supply. We conclude that the presence of pulsatile flow should be considered as a vital condition for a successful long-term survival after total artificial heart implantation.

Maintenance of the internal environment in total artificial heart (TAH) recipients during long-term pumping.

Sixty-six long-term experiments were performed on animals (65 calves, 1 goat) after implantation with a total artificial heart (TAH). Animal survival ranged from 30 to 314 days using TAH devices ranging from the TNS-BRNO-II to the TNS-BRNO-VIIII. In these experiments some basic problems were studied which need to be overcome to achieve the optimal physiological status of the animal, the optimal maintenance of the internal environment, and the long-term survival of TAH recipients. The problem areas studied were: the vasomotor regulation of the periphery, the prevention of calcification of the driving diaphragms, the optimal regulation of homeostasis, and the pathogenesis and prevention of infection. The basic precondition for the experiments was the problem-free implantation of a TAH and the subsequent optimal method of postoperative care was investigated. By the gradual multifactorial solution of these individual problems, the prolongation of the survival period of experimental animals was achieved. The definite solution and elucidation of some complications during long-term survival is still an open problem because the multifactorial events that influence long-term TAH survival are often very complicated and can sometimes only be solved by overcoming numerous obstacles as a result of the deep functional interrelationships of the disorders present.

Pathogenesis of various forms of infection in artificial hearts.

Implanted biomaterials are often inevitably attacked by the bacterial infection. So far this problem has not been sufficiently explained and solved. It represents an 'evergreen' in the artificial heart research. Infection of biomaterials is a completely new clinical entity that profoundly differs from the common clinical course of various kinds of infections and their treatment. These infections are persistent; they resist host defense mechanisms and antibiotic therapy because the nature of these microorganisms has changed due to their protection by the biofilm of some bacteria on the surfaces of implanted biomaterials. In our 66 long-term experiments with total artificial heart (TAH) in 25 animals, the infection and sepsis were the main causes of death. The different organs, attacked by the bacterial and septic complications, varied from case to case as the predominant organs, the function of which ceased to be compatible with further survival. The main foci where the infection started were also very variable. The artificial hearts used in these 25 calves were predominantly of TNS-BRNO-VII type (19 animals), TNS-BRNO-II type (4 animals) and of ROSTOCK TAH type (2 animals). The decrease of the immune defense in the TAH recipients of different intensity was evident during the course of infectious process and simultaneously, the virulence and resistance of the microorganisms against antibiotics substantially increased. The activity of the infectious agents was often combined with increased blood coagulation and thrombi formation. In 5 calves hemolytic and hemorrhagic episodes were observed, and in 15 calves without simultaneous anti-calcification treatment, a primary calcification of driving diaphragms was observed. A common dystrophic calcification sometimes complicated septic thrombogenesis. The tactics of the antibiotic therapy differed according to the results of hemocultivation tests and body temperature and was often supported by the stimulation of the immune resistance. In 2 cases we used the coating of blood chamber and driving diaphragm with albumin and hydrophilic polyurethane in order to show whether this changed surface will influence positively or negatively the bacterial seeding on the biomaterial surface. We assume the infections in the TAH recipients to be a multi-factorial process, and therefore the prevention and therapy ought to be also multi-factorial. We tried to respect this approach and we were able to increase the survival from 39 to 293 days.