652 Benefits of Ambulatory Axillary Intra-Aortic Balloon Pump for Circulatory Support as Bridge to Heart Transplant

Abstracts Results: Computational fluid dynamics results have converged to a blade design that provides superior hydraulic performance over our previous PediaFlow prototypes. Platelet activation and blood damage models predicted minimal blood damage at a flow rate of 2.0 LPM. Bench top testing of the conformal cannula demonstrated excellent deployment and fit with the next step being in vivo validation studies. Conclusions: Based on the success of prior prototypes and the computational and bench results for the newest PediaFlow prototype, system integration of the cannula, pump, and controller is now underway. Pump builds and verification both in vitro and in vivo will then follow. 651 The Ension Pediatric Cardiopulmonary Assist System (pCAS): Progress and Current Status P. Wearden,1 G. Johnson,2 P. Cahalan,2 M. Gartner.2 1Children’s Hospital, Pittsburgh, PA; 2Ension, Inc, Pittsburgh, PA. Purpose: The Ension pediatric cardiopulmonary assist system (pCAS) has been developed as a next-generation extracorporeal membrane oxygenation (ECMO) system providing increased functionality and blood compatibility. The purpose of the current work is to finalize and qualify the design in preparation for a clinical trial. Methods and Materials: The pCAS is intended to provide partial or complete cardiopulmonary support to patients from 2 kg to 25 kg for periods of up to two weeks using a single disposable integrated pump-oxygenator. The pCAS system has been specifically designed to accommodate support beyond this two-week period by rapid change-out of the pump-oxygenator. The system offers advantages over currently available systems including improved blood compatibility, smaller surface area and blood priming volume, more rapid deployment, and a compact size that facilitates parentchild bonding. An engineered bioactive surface (Ension Bioactive Surface) has been developed to mitigate adverse reactions to device surfaces and the need for high levels of anticoagulation. In vitro testing has included extensive mock circulatory loop evaluations for blood compatibility using both animal and human blood-based assays. In vivo testing has included piglets (acute) and calves (chronic) to evaluation hemodynamic functionality and long-term blood compatibility. Results: Data from in vitro and in vivo testing confirms the pCAS system is achieving performance objectives. In preparation for submission to FDA, design of componentry such as the control console enclosure, the software specification, the seal and bearing subsystem design, and the Ension Bioactive Surface are being finalized. In addition, the qualification test plan and clinical trial plans are nearing completion. Conclusions: The ability of the pCAS to provide the necessary cardiopulmonary support for the intended patient population has been demonstrated. In vitro and in vivo results strongly suggest that blood compatibility will be significantly enhanced. 652 Benefits of Ambulatory Axillary Intra-Aortic Balloon Pump for Circulatory Support as Bridge to Heart Transplant R. Umakanthan, S.J. Hoff, M.A. Wigger, N.V. Solenkova, A. Lenneman, M. Leacche, T.G. DiSalvo, M.E. Keebler, H. Ooi, A.J. Naftilan, J.G. Byrne, R.M. Ahmad. Cardiac Surgery, Vanderbilt Heart & Vascular Institute, Nashville, TN. Purpose: Axillary intra-aortic balloon pump (IABP) therapy has been described as bridge to transplant. Advantages over femoral IABP include reduced incidence of infection, longer duration of therapy, and enhanced patient mobility. We sought to identify the population that would benefit from axillary IABP support while awaiting heart transplant. Methods and Materials: We conducted a retrospective review to evaluate outcomes following axillary IABP. This included device complications, duration of support, and success in bridging to transplant. Results: Between September 2007 to 2010, Status 1B patients underwent axillary IABP insertion. All patients had ambulatory IABP placed through the left axillary artery with a Hemashield side-graft. Prior to

S217 axillary IABP, patients underwent femoral placement to demonstrate hemodynamic benefit. Duration of support ranged from 5-63 days. There was marked improvement in CI, reduction in mean PA pressures and CVP, and minimal blood transfusions. There were no device related infections. There were 3 device failures requiring IABP replacement. Seventy two percent of the patients were bridged to transplant. Data are presented in Table 1. Table 1

●●● Pre-IABP (n⫽18)

CI PA sys PA mean CVP Creatinine PRBC 24 hours postop IABP Related Infection IABP Failure Time to extubation (hrs) Survival 1 month 6 months No. transplanted Days to transplant

1.91 54.6 38.8 24.1 1.61

⫾ ⫾ ⫾ ⫾ ⫾

0.48 17.8 12.4 8.4 0.61

Post IABP (n⫽18)

p-value

2.84 ⫾ 0.70 46.7 ⫾ 13.2 31.6 ⫾ 9.7 16.1 ⫾ 7.1 1.46 ⫾ 0.15 0.11 ⫾ 0.32 None 3/18 (17%) 0.64 ⫾ 1.65

0.002 0.023 0.004 0.001 0.165

16/18 (89%) 13/18 (72%) 13/18 (72%) 26.7 ⫾ 17.7 (Median: 19, Range: 5-63)

Conclusions: Axillary IABP provides excellent support for selected patients as bridge to transplant. These include patients with prior sternotomy, elevated PRA, and small body habitus. Significant improvement in hemodynamic parameters were observed. Majority of patients were successfully bridged to transplant and discharged. This may provide a cost-effective option as a bridge to transplant in appropriately selected patients. 653 Reverse Remodelling in Partial Mechanical Circulatory Support F. Rega,1 J. Geens,1 M. Martin,2 W. Kerkhoffs,2 D. Burkhoff,2 B. Meyns.1 1Cardiac Surgery, University Hospitals Leuven, Leuven, Belgium; 2CircuLite, Inc., New Jersey, NY. Purpose: Full left ventricular (LV) unloading of at least 40 days induces LV reverse structural remodelling, evidenced by normalization of passive end-diastolic pressure-volume relationships (EDPVRs). We hypothesize that partial unloading induces reverse remodelling to a certain extent. Methods and Materials: Passive LV EDPVRs were obtained from explanted hearts of 19 patients with chronic heart failure (CHF) undergoing heart transplantation without LV support, 19 CHF patients with full and 5 with partial support before transplantation, and 5 normal human hearts not suitable for transplantation. LV support was at least 40 days. Pressurevolume relationships were measured immediately after explantation of the heart by progressive inflation of a fluid-filled intraventricular balloon with increments of 10mL, while monitoring the pressure inside the balloon at each increment.[figure1]LV dilatation was indexed by the volume at which LV pressure reached 30 mmHg. Results: The volume at which LV pressure reached 30 mmHg was the smallest in healthy hearts (95⫾12mL); in patients with partial unloading (196⫾22mL; p⫽0.03, compared to unsupported hearts) it was significantly smaller than that of the chronically failing unsupported hearts (265⫾60mL), but larger than the fully supported hearts (150⫾30 mL; p⬍0.001, compared to unsupported hearts). Conclusions: Partial mechanical unloading induces reversal of LV dilatation, but to a lesser extent than full LV support.