LEFT-VENTRICULAR SUPPORT WITH THE IMPLANTABLE AB-180 CENTRIFUGAL PUMPIN SHEEP WITH ACUTE MYOCARDIAL-INFARCTION

A small, 257 g centrifugal pump was tested as a left ventricular assis t device (LVAD) in sheep given a myocardial infarction. Pump performan ce, hemolysis, end organ function, weaning, explant procedure, and the incidence of thromboemboli at autopsy were studied over intervals of 1 to 44 days. Twelve sheep were given acute myocardial infarction by l igation of the anterior descending coronary artery and 11 had insertio n of the AB-180 Circulatory Support System (CSS). One sheep served as a control for the space occupying effects of the pump in the left ches t. Inflow was from the left atrium and outflow was to the descending t horacic aorta. Heparin (57-83 U/ml) in sterile water was infused into the pump at a rate of 10 ml/hr. Pump flows of 1-5.7 L/min were tested. The An-inn CSS supported 73.5% of the total cardiac output (pump + he art) of 3.89 L/min, with a mean arterial pressure of 86 +/- 7 mmHg at a pump speed of 4,162 +/- 276 rpm immediately after implant Hemolysis was <10 mg/dl and activated partial thromboplastin time (aPTT) values were in the normal range for sheep (<52 sec) after 48 hr of pumping. L iver enzyme concentrations returned to normal within 2 weeks. There wa s no evidence of thrombocytopenia. No signs of infection were present during assist and none was found at autopsy. The device was successful ly removed three times without the use of presser agents or blood tran sfusion. Alarm systems performed appropriately. During the 106 days of cumulative pumping, two sheep showed small (<1.5 cm) renal infarcts. Both were associated with intervals of pump stasis. The AB-180 CSS pum p was easily implanted into the left chest without the use of cardiopu lmonary bypass, It appears to have a low thromboembolic potential in s heep, without the need for large doses of heparin to elevate aPTT valu es. This characteristic may ameliorate the excessive bleeding seen cli nically with current LVAD systems used for post cardiotomy cardiogenic shock, which require anticoagulation with heparin. The small size and weight of the device permit implantation within the chest and allow c hest closure. This may reduce the incidence of infection associated wi th temporary left ventricular assist and an open sternum.