CARD25: Development of a Minimally Invasive Single Port Pulsatile Ventricular Assist Device

Abstract

Purpose: Our goal is to develop a compact, single port, pulsatile ventricular assist device (VAD) for total left ventricle (LV) support that only requires a minimally invasive single cannulation from apex to aorta. Methods: Standard diaphragm displacement pumps have 2 valved ports and inlet/outlet cannulas to alternate between blood infusion and withdrawal. By contrast, our compact single port pulsatile VAD consists of a valved single lumen cannula and a valveless single port diaphragm displacement pump. Via a small left thoracotomy, the valved single lumen cannula is inserted from apex to aorta (Fig). Four one-way inlet valves on the valved single lumen cannula wall allow blood withdrawal from LV, and a tri-leaflet outlet valve at the cannula tip allows blood delivery to aorta. The 28 Fr valved single lumen cannula prototype was made as one piece by polyurethane (PU) dip molding with memory alloy reinforcement. The two halves of the valveless single port diaphragm displacement pump prototype housing were made by polycarbonate vacuum thermoforming and assembled with a flexible PU membrane diaphragm in the middle to separate the blood and pneumatic chambers. This pump had a 60 cc stroke volume. A closed mock loop with 37% glycerin was used to mimic the LV-aortic valve-ascending aorta tract. Priming volume and reservoir height were adjusted to maintain 70 mm Hg diastolic aortic pressure and 16 mm Hg preload. Circuit flow and pressure in valved single lumen cannula were recorded. The catheter introducer with pressure transducer on tip was inserted through apex in adult sheep (n=5, 44-52 kg), with pressure wave form guiding tip into ascending aorta. The valved single lumen cannula slid along introducer through apex, crossing aortic valve, with its tip in ascending aorta. The valved single lumen cannula was connected to the single port diaphragm displacement pump. Pumping was increased for a normal cardiac output. The single port pulsatile VAD prototype performance was assessed for 6 hrs with hemodynamics/blood counts recorded. Results: The valved single lumen cannula and single port diaphragm displacement pump prototypes were fabricated as designed. The bench study showed that the single port pulsatile VAD achieved a pumping flow of up to 3.75 L/min. Valve regurgitation was <3%. In the sheep study, the valved single lumen cannula was easily installed within 1 min at first attempt. The single port pulsatile VAD achieved maximal 3.75 L/min pumping flow in a 52 kg sheep. The single port pulsatile VAD had consistent pumping flow through 6 hrs with stable hemodynamics (Table). Hemoglobin and platelet/white blood cell counts were unchanged. No obvious injury or thrombosis in heart or single port pulsatile VAD were observed at necropsy. Conclusions: Our single port pulsatile VAD only requires a single apex cannulation with valved single lumen cannula to achieve reliable LVAD performance, showing great promise for a short to mid-term minimally invasive LVAD.Figure 1. Our single port pulsatile ventricular assist device with a valved single lumen cannula and a valveless single port diaphragm displacement pump. Table 1. - Hemodynamics and Blood Count Results Sheep 1-5 Baseline Pump Run1 hr Pump Run3 hr Pump Run6 hr sABP (mm Hg) 111±15.5 138±19.5 122±16.4 113±16.2 CVP (mm Hg) 11±0.4 11±0.8 11±0.5 11±0.8 CO (L/min) 2.5±0.38 3.8±0.98 3.6±0.66 3.5±0.66 Pump Flow (L/min) 0±0 2.8±0.65* 2.7±0.65* 2.7±0.52* HR (bpm) 154±61.1 104±44.7 105±39.3 127±16 WBC (103/uL) 4.1±0.14 N/A N/A 4.8±2.57 PLT (103/uL) 467±93.3 N/A N/A 380±171 HgB (g/dL) 9.4±0.45 N/A N/A 9.1±0.38 * p<0.05 vs Baseline sABP=systolic arterial pressure, CVP=central venous pressure, CO=cardiac output, HR=heart rate, WBC=white blood cell count, PLT=platelet count, HgB=hemoglobin, and N/A=not applicable.