LV hypertrophy and increased LV mass were highly correlated with sudden death, congestive heart failure, stroke, myocardial infarction, coronary artery disease, and other cardiovascular events.41
Incomplete regression of LV mass and LV function after AVR was also related to poor long-term survival.42
Therefore, pressure gradient across the implanted valve is one of the most important issues in AVR.
Early postoperative hemodynamic performance was not different between stentless and stented valves, though implanted valve size was larger in stented AVR.43
The hemodynamic advantage of stentless AVR is not unanimous, though stentless valves one size larger could be implanted if the aortic annulus has the same size. Subcoronary implantation of stentless prostheses does not necessarily allow for larger valve selection compared with stented valves, because the LV outflow suture line is within the aortic annulus. The stented valves can be placed in a supra-annular position, upsizing from the true aortic annular size. New-generation Carpentier–Edwards Perimount Magna (Edwards Life-sciences, Irvine, CA) valves had a better hemodynamic performance compared with stentless Edwards Prima Plus (Edwards Lifesciences) valves regarding pressure gradient and effective orifice area.47
No difference was found when the Prima Plus valve was compared with the Perimount pericardial valve.37
Compared with porcine stented valves, hemodynamic performance was better with stentless valves.39
A faster and better recovery of LV function and mass has been reported after stentless AVR.36
Implantation technique was also related to the improved hemodynamics. A full-root technique can implant a larger stentless valve in the supra-annular position, allowing upsizing, compared with the original aortic annulus.58
There may be a bias in the selection of stentless or stented valves by surgeons, because more complicated aortic root anatomy leads to the more frequent selection of stented valves in the learning curve period.
In randomized studies, better hemodynamic results were obtained with Freestyle,57
and Toronto SPV valves20
compared with stented valves. Although Freestyle valves showed a greater reduction in peak velocity and a greater increased effective orifice area than Mosaic porcine valves, there was a similar reduction in LV mass index and clinical outcomes at 6 months and 12 months after the operation.57
Narang et al60
compared the Freestyle valves with Carpentier–Edwards Perimount valves. LV ejection fraction, LV mass, New York Heart Association scale, and mean pressure gradient were similar in both groups. However, in patients with LV ejection fraction less than 50% and implanted valve less than 19 mm, there was a significant difference in LV mass index and mean pressure gradient. Sorin Freedom stentless valves had a better pressure gradient and effective orifice area than Sorin More stented valves.21
However, there was no significant difference in LV mass index at 12 months after the operation. Ali et al48
compared Prima Plus valves with Carpentier–Edwards Perimount valves. There was no difference in mean pressure gradient and LV mass 8 weeks postoperatively. Similar results were obtained by Doss et al61
and Risteski et al62
in patients over the age of 75 years. Chambers et al20
and Cohen et al43
compared Toronto SPV valves and Carpentier–Edwards Perimount valves in a randomized fashion. The effective orifice area, mean pressure gradient, and LV mass index were similar 12 months after the operation.
Stentless valves showed no pressure gradient during dobutamine stress echocardiography in comparison with elevated transvalvular gradient in mechanical valves.45
Several studies demonstrated superior hemodynamics under exercise with stentless valves compared with mechanical valves after AVR.63
Fries et al44
compared 23 mm Freestyle valves implanted by the full-root technique with native aortic valves and 23 mm Carpentier–Edwards Perimount valves. There was a significant increase of pressure gradient in the stented valve group under exercise, though the native valve group and the stentless valve group showed no increase in pressure gradient under exercise.
An improved hemodynamic performance resulted in faster LV mass reduction in patients with aortic stenosis and LV hypertrophy.65
A meta-analysis showed a faster LV mass reduction in patients with stentless AVR than in those with stented AVR.52
However, some studies showed no differences in LV mass reduction.57
Although faster LV mass regression has been reported after stentless AVR, it was obtained by larger valve implantation, and final LV mass regression was not significant 1 year after AVR.21