Background and aim of the study: Stentless valves are considered to exhibit better hemodynamics after aortic valve replacement (AVR) compared to stented valves. However, a new generation of stented bioprostheses for completely supra-annular implantation has been designed to optimize the ratio of the effective orifice area (EOA) of the prosthesis and aortic annulus area. The study aim was to determine whether a stentless valve implanted in the subcoronary technique renders larger orifice areas and lower transvalvular pressure gradients at rest and exercise compared to a completely supra-annular stented device.
Methods: Twenty patients underwent AVR for aortic stenosis with the St. Jude Medical (SJM) Toronto Root stentless porcine bioprosthesis, using a subcoronary implantation technique. Through the authors' institutional database, 20 additional patients were identified who had undergone AVR with the Medtronic Mosaic stented completely supra-annular porcine bioprosthesis. The patient groups were not matched for labeled valve size, but for annulus diameter measured intraoperatively using Hegar's dilators. Hemodynamic performance was assessed by transthoracic echocardiography at discharge (early) and by rest and stress echocardiography at six months postoperatively (mid-term).
Results: Transvalvular mean pressure gradients (MPG) at rest were significantly lower in the stentless group, but cardiac output was similar in both groups. Stress echocardiography also revealed significantly lower gradients at 25 W and 50 W exercise in the stentless group. The EOA index (EOAI), grouped by annulus diameter, tended to be larger in the stentless group and showed no severe patient-prosthesis mismatch (PPM; EOAI <0.65 cm2/m2) which, in contrast, occurred in three patients (15%) in the stented group (p = 0.072).
Conclusion: In summary, the SJM Toronto Root porcine stentless bioprosthesis in the subcoronary position showed lower MPGs and larger EOAs at rest and during exercise compared to the Medtronic Mosaic porcine stented bioprosthesis. Therefore, physically active patients in particular may benefit from use of the stentless valve. Because of its larger EOA, a stentless valve should be implanted if severe PPM is expected.