Background and aim of the study: Coronary perfusion is impaired in patients with aortic stenosis (AS). Aortic valve replacement (AVR) leads to improvement, but not complete restoration, of coronary flow. Previous studies have shown that postoperative coronary flow rate and coronary reserve in mechanical valves is dependent on valve design and orientation. The study aim was to investigate acute changes in coronary perfusion in patients undergoing mechanical or biological valve replacement in a prospective, randomized clinical study.
Methods: Forty patients undergoing AVR for AS underwent MRI scanning to measure coronary flow preoperatively and at five days after surgery. Patients scheduled for mechanical AVR (n = 20) were randomized to a tilting disc (Medtronic Hall) or bileaflet (Medtronic ADVANTAGE) prosthesis; the biological-valve group (n = 20) received a stented (Medtronic Mosaic) or stentless (Medtronic Freestyle) valve. Valve sizes were comparable in all groups. Patients also underwent echocardiography both preoperatively and postoperatively to measure transvalvular pressure gradients. The rate-pressure product (RPP) was calculated as a marker of

myocardial oxygen demand and cardiac workload.
Results: The mean preoperative coronary flow rate was 90 ± 32 ml/min, and this increased after AVR in all patients. The rise in the mechanical-valve groups was comparable for the two tested valves, whereas in the biological-valve groups a significantly higher increase for stentless valves was present (p <0.05). Mean pressure gradients for the Hall and ADVANTAGE valves were equal; for biological valves, the Mosaic demonstrated a higher mean gradient (19 ± 6 mmHg) than the Freestyle (10 ± 4 mmHg) (p <0.05). The RPP was lower for ADVANTAGE (mechanical group) and for Freestyle valves (biological group).
Conclusion: Coronary artery flow was increased following AVR in all valve groups. The rise was significantly more distinct for Medtronic Freestyle stentless valves compared to the three other valve substitutes. As the stentless design also demonstrated superior hemodynamics and a lower myocardial oxygen demand with lower pressure gradients and lower RPP, this may have a positive impact on the clinical long-term outcome of this valve.
The Journal of Heart Valve Disease 2006;15:5-11