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Serum lactate dehydrogenase (LD) patterns of 16 calves with total artificial heart (TAH) were studied to identify a mean LD pattern in their serum (survival 51-293 days). Evaluations were made by the sum of vectors method (SV). The mean LD pattern was determined from serum LD patterns, interval days of 33 - 49 with TAH. Serum LD patterns of control and mean LD pattern differed significantly (n = 12, P < 0.05) in single isoenzymes and resultant vectors as the representatives of LD patterns. The different tissues with an increased risk of being affected were identified by evaluation of LD patterns in the serum of calves within term without perceptible acute damage and in the terminal stage of experiments. Such identified organs suggest that the organism under study is out of balance and specific treatment is needed.

Changes in serum proteins, enzymes and isoenzymes of lactate dehydrogenase (LDH) were compared in long-term surviving calves with a total artificial heart without influencing their central venous pressure (CVP) and calves in which CVP was lowered by antihypertensive drugs administered from day 60 to the end of the experiment. Antihypertensive drugs helped keep CVP within physiological levels for longer and aided liver function as well as evidenced by the different values for the parameters studied in the two groups.

Evaluation of five longest surviving calves among a total of 54 longterm survivors, at the Brno Research Centre was performed. These calves were treated by administration of antihypertensives and partially by electrical stimulation of the right atrium to reduce central venous pressure (CVP). Treatment for CVP was effective, as compared with two groups of 5 calves each not treated in this way, and it is assumed to be an important factor for prolongation of survival. Mineralization of driving diaphragms was present in all these calves. No preventive measures of this pathologic change were performed in this group. Another complication is hemolysis, which is partly caused by immune mechanisms initiated by administration of alpha-methyl dopa and partly by mechanical destruction due to a heavily mineralized driving diaphragm. The prevention of mineralization is another important problem for future research. Other problems, concerning the survival of TAH recipients are discussed.

A polymethylmethacrylate total artificial heart (kinetic components made of polyetherurethane) of TNS Brno II type was implanted into seven calves (2-5 months of age) surviving for the average of 152.4 +/- 19.1 days after the implantation. During the entire post-operative period the animals received oral warfarin-sodium, acetylsalicylic acid, dipyridamole and alpha-tocopherol. Blood was taken for biochemical and hematological examinations twice a week from the jugular vein. During the experiments there were decreases in the number of red blood cells, hematocrit and hemoglobin levels. Plasma free hemoglobin and serum enzymes (alkaline phosphatase, AST, ALT, LDH) increased. Coagulation tests were abnormal because anticoagulation therapy was used. There were minimal changes in the number of white blood cells and platelets, fibrinogen, blood pH, blood glucose, serum electrolytes, bilirubin (total and direct), creatinine, blood urea, and lactate. Possible reasons for observed changes include the gradual rise in the central venous pressure and damaged function of the liver parenchyma. Other factors playing a possible role in inducing changes in laboratory findings are also discussed.