Do valved stents compromise coronary flow?☆

OBJECTIVE: The aim of the present study is to evaluate a new self-expanding valved stent design for minimal invasive aortic valve implantation and its interference with coronary flow. METHODS: An equine pericardial valve mounted onto a self-expanding nitinol stent (3F Therapeutics trade mark, CA, USA), outer diameter 23 mm, was evaluated (A) in vitro in a dynamic pulsatile mock loop and (B) in vivo in six calves (75+/-2. 5 kg). In four animals valve stents were implanted on-pump and in two animals off-pump after induction of ventricular fibrillation. Target site for deployment was the orthotopic aorta, over the native valves. In vivo assessment was performed with intracardiac (AcuNav) and intravascular ultrasound including leaflet motion, planimetric valve orifice and residual-coronary-stent-index (RCSSI, distance stent to aortic wall/coronary diameter) calculations, coronary blood flow characteristics, transvalvular gradient, regurgitation and paravalvular leaking, in combination with continuous cardiac output measures. Macroscopic analysis was performed at necropsy. RESULTS: Two-dimensional intracardiac ultrasound showed good leaflet motion, with full valvular opening and closing in five of six valves. Planimetric valve orifice was 1. 75+/-0. 4 cm (2). There were no signs of coronary flow impairment with an RCSSI of 1. 8+/-1. 2. The implanted valved stents showed a low transvalvular gradient of 5. 3+/-3. 9 mmHg (mean, peak-to-peak) on invasive measurements and 4. 7+/-2. 5 mmHg in two-dimensional intracardiac sonography. One of six valves showed mild to moderate regurgitation and one of six valves a minor to moderate paravalvular leak due to size mismatch. CONCLUSIONS: This new self-expanding valved stent design allows for on- and off-pump aortic valve implantation in the orthotopic aorta, over the native valves without interference of the coronary blood flow and excellent acute valve function in properly sized devices.