Apical-Ventricular Cannula for Aortic Valve Bypass Therapy
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A growing number of elderly patients with significant co-morbidities do not meet the inclusion criteria for conventional cardiac surgical therapies, including aortic valve replacement and mechanical circulatory support. To meet this clinical need, an aortic valve bypass (AVB) system is being developed that may be implanted using subcostal or mini-thoracotomy surgical approaches without ventricular coring or cardiopulmonary bypass. The AVB system consists of an apical left ventricular (ALV) cannula made from pyrolytic carbon, a valved conduit with a locking mechanism, and a Nitinol clip for anastomosis to the descending aorta. To define design criteria and demonstrate efficacy, ALV cannulae with different diameters (7–14 mm), number of sideholes (6–12), sidehole size (1.9–4.6 mm wide) and tip shapes (tapered, straight) were designed, fabricated, and tested. Cannula efficacy was determined by quantifying flow rates and pressure drops across the ALV cannula using steady-state and dynamic mock circulation models simulating mild, moderate and severe aortic stenosis test conditions. Blood trauma testing was conducted to demonstrate hemocompatibility using the smallest diameter (7 mm) ALV cannula prototype fabricated from pyrolytic carbon (PYC). In vitro and blood trauma testing demonstrated that (1) the 7 mm PYC cannula did not produce significant hemolysis (<40 mg/dL pfHb), but was unable to achieve bypass flow rates above 1.4 L/min, (2) a minimum cannula diameter of 12 mm was required to produce flow rates >4.5 L/min for <10 mmHg pressure drop across the ALV cannula, and (3) the cannula tip shape did not significantly alter bypass flow rate or pressure drop. The ALV cannula may enable a minimally invasive surgical approach using a modified Seldinger’s technique for implantation in heart failure patients with aortic stenosis.
KeywordsAortic stenosis Cannula Heart failure Ventricular unloading
This work was supported by the Roger M. Prizant Research Trust Fund for ventricular assist device-related research at the University of Louisville.
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