Development of an Equine Ex Vivo Pulmonary Arterial Perfusion System

Pulmonary artery calcification has been reported in racehorses. This vascular lesion is associated with arterial stiffness, which is considered the best predictor of many human cardiovascular diseases. Interestingly, horses experience catastrophic vascular rupture and exercise induced pulmonary hemorrhage (EIPH). Pulse wave velocity (PWV) is, currently, the most common clinical measure of arterial stiffness in humans, and may be useful in the study of equine cardiovascular disease. In order to measure PWV and evaluate pulmonary vascular stiffness, a precise method of catheter placement in the equine pulmonary artery is required as fluoroscopic guidance is precluded in the horse. The behavior of catheters within the pulmonic vasculature was investigated using equine en bloc heart and lung preparations. An ex vivo pulmonary arterial perfusion system (EVPAPS) with controlled pulsatile flow, perfusate temperature and ventilation was designed and constructed. A blind technique for catheter placement into the distal main stem f the pulmonary artery utilizing balloon tipped catheters was evaluated. Catheter performance was observed with an intravascularly placed endoscope. Three balloon catheters were selected for navigation trials; a 4mm diameter x 1.2cm, 2.7Fr, 142cm angioplasty catheter (C4mm); a 10mm diameter x 4cm, 5Fr, 150cm angioplasty catheter (C10mm); and a 16mm diameter, 7Fr, 200cm pancreatic duct sphincteroplasty catheter (C16mm). A successful catheter insertion event was defined as insertion within a left or right main stem to a distance greater than 20 cm beyond the bifurcation. The 16mm catheter was superior with an average proportion of successful insertions (PSIavg) of 93.6%; an average insertion distance in the main stem (IDMavg) of 30.1±5.68 cm; and an average insertion distance anywhere in the pulmonary artery (IDAavg) of 29.3±6.42cm verses the 10mm (PSIavg 25%, IDMavg 39.3±11.4cm, IDAavg 19.3±15.1cm) and 4mm (PSIavg 11%, IDMavg 40.0±11.0cm, IDAavg 12.8±13.2cm) respectively. The C16mm was then used in the EVPAPS to place, via over the wire exchange, a dual pressure sensor catheter in 2-heart and lung preparations and PWV data was collected. An equine ex vivo pulmonary arterial perfusion model was developed and functioned with sufficient fidelity to establish a method of blind catheter placement in the equine pulmonary artery.