Background and aim of the study: The study aim was to investigate the in-vivo flow profiles of a stentless aortic bioprosthetic valve by MRI flow quantification, and to identify the clinical implication of prosthesis size and implantation method.
Methods: Twenty-six patients with a Freestyle stentless aortic bioprosthetic valve were studied using three-dimensional flow velocity profile by MRI, and compared with four patients with a stented aortic bioprosthetic valve and four healthy volunteers. Flow velocity profiles were analyzed quantitatively by the hydromechanics parameter, mean to peak velocity ratio at peak systole and compared with parameters monitored echocardiographically.
Results: In larger-sized valves or full root implantation, flow profiles showed an optimal pattern with low gradients, a high mean to peak velocity ratio, and

minimum disturbance which approximated that of a normal valve. By contrast, a subset of patients, notably with 21 mm valves and subcoronary implantation, showed suboptimal flow pattern with high gradient and low mean to peak velocity ratio which approximated that of stented valves. The mean to peak velocity ratio was more strongly related to peak velocity than to the indexed effective orifice area.
Conclusion: Although stentless aortic bioprostheses have excellent hemodynamic performance, some patients show suboptimal results. This seems to occur more often when the subcoronary technique is used, and especially with 21-mm valves. Care must be taken when using the subcoronary technique with a 21-mm valve in patients with a small body surface area.

The Journal of Heart Valve Disease 2005;14:630-636