This study was performed in a university laboratory environment using Thiel embalmed human cadavers. The study was conducted by an interventional cardiologist (PR) familiar with intra-arterial access and fluoroscopic imaging. The SAAP catheter was an experimental catheter prototype that was 800mm long with an 11.5 Fr outer diameter (Vention Medical Inc, USA). It had a 7.5 Fr central lumen, and a 30mm (17ml) semi-compliant balloon near the tip that was inflated via a separate lumen. (Fig. 1) Multiple catheters were used throughout the study. The study was performed four times, with the same SAAP catheter used in each trial.
Cadaveric aortic flow and SAAP cannulation
Two cadavers were preserved using the Thiel technique.[16 17] A previously validated method to establish extracorporeal driven ante-grade aortic flow within the cadaver was adapted to deliver extracorporeal flow retaining the Thiel cadaver completely intact without chest plate removal.[18] This provided anatomically accurate, physiologically similar and robust model comparable to a model previously used to simulate aortic endovascular procedures.[18] Ports (16 Fr x 10cm Check-Flo, Cook Medical, USA) were placed into the cadaver’s left and right subclavian arteries and connected to a cardiopulmonary bypass machine (HL30 Maquet, Germany). A modified master pump recreated pulsatile flow at 60 beats per minute. The master pump was prepared with 6m of 13mm diameter silicone-platinum coated tubing (Silex, UK), delivering a flow rate of approximately 2.5L per minute as the standard setting. Two 14 Fr vascular access sheaths (Medtronic, UK) fitted with a haemostatic valve adapter were placed in the left and right common femoral artery using an open surgical cutdown technique and sutured in place. Through this, the SAAP catheter (Vention Medical Inc, USA) was introduced over a 180cm, J-tipped 0.035” PTFE-coated wire (Amplatz super-stiff, Boston Scientific, USA). Pressure transducers (TruWave, Edwards Lifesciences, USA) were connected to a haemodynamic monitoring system (M3046A, HP, Germany) to provide a continuous pressure measurement at three separate sites: extracorporeal circuit, descending thoracic aorta and abdominal aorta.
Positioning of the SAAP Catheter and Balloon Inflation
Once pulsatile flow had been established in the cadaver’s central vasculature the SAAP device was inserted via the right common femoral artery. Appropriate positioning of the SAAP catheter was achieved using fluoroscopic guidance (OEC Elite 9900 C-arm, GE, USA) at 8–12 frames per second (fps), and digital subtraction angiography at 25 fps. The balloon end of the SAAP device was positioned in the descending aorta, distal to the left subclavian artery. Once in position, the balloon was inflated under live fluoroscopic guidance. A 50:50 mix of normal saline and iodinated contrast medium (Omnipaque 300, GE Healthcare, Auckland) was used to inflate the balloon. Aortic apposition was confirmed radiologically, by tactile assessment, and by changes in the extracorporeal flow and pressure indications.
Aortic arch perfusion and direct coronary artery access
Following successful inflation of the SAAP balloon in the descending aorta, a 30ml bolus of 50:50 saline-contrast mix was delivered through the central lumen of the SAAP catheter to the aortic arch via an autoinjector. Cine-fluoroscopy was continued during this process, to assess whether coronary flow was achieved. To assess the feasibility of achieving direct coronary access via the SAAP catheter a Judkins left 4.0 5Fr coronary guiding catheter (Vista Brite Tip, Cordis, UK) was placed through the SAAP catheter. This was performed after the SAAP balloon was inflated in the thoracic aorta. Using standard techniques engagement of the left main stem was attempted, confirmed with hand-injection of contrast via a conventional syringe-manifold.
Identifying procedure success and complications
Systematic post hoc review of the images was performed to identify correct device placement, overt aortic injury, subtle intimal damage and dissection, ability to deliver bolus to aortic root, balloon patency, aortic valve position, positive carotid, and coronary artery flow.
Ethical considerations
Study procedures involving human cadaveric participants were carried out in accordance with current anatomical legislation, the Anatomy Act 1984 and Human Tissue (Scotland) Act 2006.