Summary. Intra.thoracic total replacement of the heart by double-chambered pneumatically driven blood pumps was carried out in 18 sheep with an average bodyweight of 59 kg.The animals were narcotized with thioarbiturate and then tracheotomized. The thorax was opened by median sternotomy and the animal joined to a heartlung-machine. An absolutely blood-and air-tight connection between the delicate and easily ruptured atrial tissue and the relatively rigid atrial connections of synthetic material of the artificial heart, has to be established. During the operation difficulties arise--in the same way as in the case of homologous heart transplants--with the suture of the short and easily ruptured atrial septum. Therefore the atrial septum is first reinforced with double pericardial flaps. In the end we found that the best method consisted of detaching the heart above the valve ring and using a continuous suture to join the Teflon connections of the artificial heart to the firm structure of the valvular ring. Plug-like connections in the shape of short tubes containing the valves were used for joining the aorta and the pulmonalis to the heart. The pressure in both atria, in one systemic artery and in the pulmonalis, as well as the blood-flow through the pulmonary artery were continuously recorded. Blood-gas analysis, blood and electrolyte counts, lactic acid, pyruvic acid and LDH determinations were carried out at regular intervals. The plasma haemoglobin and the lactic acid and pyruvic acid levels increased at different rates. Thrombocytes and leukocytes decreased in number, at times quite markedly. Most animals survived for only 2--5 hours. In one sheep a good substitution of the heart with this pump succeeded for 11 hours.Zusammen]assung. Bei 18 Schafen mit einem durchschnittlichen Gewicht yon 59 kg erfolgte ein intrathorakaler Totalersatz des Herzens durch eine zweikammerige, pneumatisch angetriebene Blutpumpe.Die Tiere wurden mit Thiobarbiturat narkotisiert und dann tracheotomiert. Der Thorax wurde durch eine mediane Sternotomie geSffnet und die Tiere an eine Herz-Lungenmaschine angcschlosscn. Es muBte eine absolut blur-und luftdichte Verbindung zwischen dem zarten und leicht zerrei~lichen Vorhofsgewebe und den relativ starren Vorhofsans~itzen des Kunststoffherzens hergestellt werden. Beim operativen Vorgehen, etwa wie bei der homologen Herztransplantation, ergaben sich Schwierigkeiten bei der Naht des stets kurzen und zerrei01ichen Vorhofseptums. Deshalb wurde zun~chst das Vorhofseptum durch gedoppelte Perikardlappen verst~rkt. Am besten bewiihrte sich schliefilich eine Methode, bei der das Herz oberhalb des Klappenringes abgetrennt wurde und bei der folgenden fortlaufenden Naht zum Anschlul3 an die Teflonansatzstutzen des kiinstlichen Herzens das feste Material des Klappenringes mitgefaBt werden konnte. Zum AnschluB an Aorta und Pulmonalis dienten Steckverbindungen in Form yon kurzcn Rohren, in welche die AusfluBklappen eingebaut waren.
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