Faculty Bibliography

OBJECTIVES: Pump-off testing to assess left ventricular recovery is not an option for continuous-flow left ventricular assist devices unless measures are taken to prevent pump regurgitation. The purpose of this bench study was to characterize the hemodynamics and pump flow of the HeartMate II (Thoratec Corp, Pleasanton, Calif) left ventricular assist device at 6000 rpm, the speed commonly used clinically to determine left ventricular recovery. METHODS: The HeartMate II device was operated in a mock loop at 3 speeds (6000, 8000, and 10,000 rpm). We acquired pressure-flow curves in each steady state. In pulsatile mode with the pneumatic ventricle (heart simulator) activated, pump flow, total flow, and aortic pressure data were obtained under conditions simulating normal heart function or heart failure. RESULTS: A large regurgitant flow during diastole was confirmed in normal heart function at 6000 rpm support; however, the net flow was zero, and there were no differences in the mean aortic pressure between 6000 rpm support and no left ventricular assist device support. In contrast, in the heart failure condition, left ventricular assist device flow at 6000 rpm significantly contributed to the mean aortic pressure and total flow because there was less regurgitant flow. CONCLUSIONS: The net pump flow generated by the HeartMate II device at 6000 rpm depends on the degree of residual left ventricular function. In the setting of improved left ventricular function, at 6000 rpm, we noted a large regurgitant flow that reloaded the left ventricle. Although this "marker" can serve as a useful indicator for left ventricular recovery, assessing left ventricular recovery at this speed is flawed unless measures are taken to prevent regurgitant flow.

BACKGROUND: Anticoagulation with warfarin is common in patients presenting for heart transplant. Prior to surgery, anticoagulation reversal is necessary to avoid significant intraoperative and perioperative bleeding complications. Commonly, warfarin reversal is achieved with vitamin K and fresh frozen plasma (FFP); however, these therapies have significant limitations. An alternative to FFP for reversal exists with prothrombin complex concentrate (PCC). A warfarin reversal protocol prior to heart transplant was implemented using low-dose PCC at our institution. OBJECTIVE: To assess blood product use, effectiveness, and safety post-low-dose PCC administration in patients needing warfarin reversal prior to heart transplant compared with historical controls. METHODS: This was a single-center, retrospective cohort study. The PCC cohort included patients undergoing heart transplant presenting with an international normalized ratio >/=1.5 on warfarin therapy and who received at least 1 dose of PCC. Blood product use was measured from postoperative day 0 to 2. RESULTS: The PCC and historical control cohorts included 16 and 50 patients, respectively. There was a significant reduction in the use of FFP (4 vs 8 units, P = 0.0239) in the PCC cohort compared with the historical control cohort. No differences were identified in the use of other blood products as well as other secondary efficacy or safety end points. CONCLUSIONS: Use of PCC, per the reversal protocol, prior to heart transplant reduced FFP use and showed a non-statistically significant trend toward reductions in the use of other blood products in the intraoperative and perioperative setting, with no difference identified in thrombotic or embolic complications compared with historical controls.

Despite significant improved survival with continuous flow left ventricular assist devices (LVADs), complications related to aortic valve insufficiency, gastrointestinal bleeding, stroke, pump thrombosis, and hemolysis have dampened the long term success of these pumps. Evolution has favored a pulsatile heart pump to be able to deliver the maximum flow at different levels of systemic vascular resistance, confer kinetic energy to the flow of blood past areas of stenosis and generate low shear stress on blood elements. In this perspective, we suggest that lack of pulsatility may be one factor that has limited the success of continuous flow LVADs and suggest that research needs to focus on methods to generate pulsatility either by the native heart or by various speed modulation algorithms.

Implantation of mechanical circulatory support devices is challenging, especially in patients with a small chest cavity. We evaluated how well the Cleveland Clinic continuous-flow total artificial heart (CFTAH) fit the anatomy of patients about to receive a heart transplant. A mock pump model of the CFTAH was rapid-prototyped using biocompatible materials. The model was brought to the operative table, and the direction, length, and angulation of the inflow/outflow ports and outflow conduits were evaluated after the recipient's ventricles had been resected. Thoracic cavity measurements were based on preoperative computed tomographic data. The CFTAH fit well in all five patients (height, 170 +/- 9 cm; weight, 75 +/- 24 kg). Body surface area was 1.9 +/- 0.3 m (range, 1.6-2.1 m). The required inflow and outflow port orientation of both the left and right housings appeared consistent with the current version of the CFTAH implanted in calves. The left outflow conduit remained straight, but the right outflow direction necessitated a 73 +/- 22 degree angulation to prevent potential kinking when crossing over the connected left outflow. These data support the fact that our design achieves the proper anatomical relationship of the CFTAH to a patient's native vessels.