Clinical application and patient selection in the use of a total artificial heart as a bridge for transplantation

Control and Treatment of Hemostasis in Cardiovascular Surgery

The hemostasis protocol applied at the Cardiovascular Surgery Dept. of La Pitié Hospital has greatly reduced thromboembolic accidents and excessive bleeding, with consequent benefits for patients as well as cost reduction. Protocol also has been adopted for patients implanted with a circulatory assist device or a TAH. This paper presents our criteria on supervision and treatment of coagulation with such patients, who reflect all the acquired pathology in clinical hemostasis. From 04/86 to 07/94, 82 patients underwent TAH as a bridge to transplantation. Mean age: 38. Overall duration of mechanical support: 1930 days (mean: 23), of which 137 and 603 for 2 patients. Average duration of CPB: 150 min. Systematic approach to complex TAH-blood interaction and pre-operative multiple organ dysfunction used to control bleeding and/or thromboembolism after CPB. In addition to routine tests, specific regular testing was carried out at least once a day for platelet functions, for thrombin formation and its regulatory pathways, and for the fibrinolytic system. Patients were treated with small doses of Heparin, large doses of Dypyridamole, small doses of Aspirin, modulated doses of Aprotinin, Ticlopidine, Pentoxifylline, FFP, as well as Fibrinogen and AT III concentrates. Dosage was adapted to patient's clinical profile as well as to test interpretation criteria to provide personalized treatment. DIC, widely present in its different phases, was thus diagnosed and treated. All DIC bleeding was controlled, making it possible to detect other causes of post-operatory bleeding and use blood derivates rationally. There were no thromboembolic complications and no iatrogenic bleeding. TAH explantation shows no evidence of macroscopic clots in high risk sites, confirmed by microscopic analysis.

Total artificial heart: destination therapy

The AbioCor is a revolutionary device. It is the only device of its kind in the clinical world. The role of the AbioCor is to provide permanent replacement of the failing heart for patients who are not transplant candidates. The clinical trial has been successful in the majority (four of seven) of patients implanted thus far. Eight more patients are required to complete the initial feasibility phase of the trial, afterwhich it remains to be seen if the trial will expand to additional patient populations. The powerful features of the pump have been demonstrated in the extremely sick group of candidates that enrolled in the study. The TET system has worked extremely well. Lastly, the milestone of discharging a patient to home on a completely internal artificial heart has been realized. The profile of CardioWest is very different from AbioCor. Although both were initially designed as permanent replacement therapies, the CardioWest has been extremely useful as a bridging device, and it may have a broader application in the future. For the CardioWest, the most favorable groups are patients with cardiomyopathy who decompensate while awaiting transplantation. On the other hand, the AbioCor is indicated in nontransplant candidates with biventricular failure who have a less than 30-day predicted survival. Proper patient selection is critical to achieving success with either device.

[Value of continuous venous blood oxygen measurement during external circulatory assistance]

A case is reported of a 40 year-old man, on the waiting-list for heart transplantation, who developed terminal heart failure. Using an Opticath catheter and a radial artery catheter, SV(-)O2 was monitored continuously, and cardiac output, pulmonary arterial and wedged pressures, and right atrial pressure were repeatedly measured. Despite appropriate treatment (adrenaline, dobutamine, glyceryl trinitrate), the patient remained in anuria and cardiogenic shock. External circulatory support (ECS) (BVS 5000 Abiomed) was therefore used as a bridge to cardiac transplantation. The resultant increase in systemic blood flow led to an early and fast rise in SV(-)O2, from 40% to 73%, with a decrease in the oxygen extraction ratio (ERO2) from 50 to 30%. Serum lactate concentrations returned to normal within the first six hours of ECS (less than 120 mg.l-1). During the first 24 h of ECS, SV(-)O2 decreased and ERO2 rose significantly on two occasions: during an episode of shivering, and another of restlessness during nursing. An attempt at weaning the patient from the ventilator at the 39th h also led to a sudden decrease in SV(-)O2, with a rise in ERO2. The Opticath catheter was finally removed after 150 h of ECS because of a decrease in reflected light intensity.