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Ann Thorac Surg 2007;84:78-79
© 2007 The Society of Thoracic Surgeons
Department of Cardiac Surgery, John Radcliffe Hospital, Oxford Heart Centre, Headington, Oxford, OX3 9DU United Kingdom
(Email: xy.jin{at}orh.nhs.uk).
A decade of extensive clinical investigations has followed the early reports of more favorable left ventricular (LV) mass regression and functional remodeling with stentless rather than stented aortic valve replacement (AVR). In contrast to the majority of previous reports, two large randomized clinical trials have recently reported insignificant differences in LV mass regression or valve hemodynamics, or both, between stentless and stented AVR. Therefore, the meta-analysis reported by Kunadian and colleagues [1] has been a timely important contribution, whereas we try to reconcile conventional wisdom with these new findings. The authors analyzed 10 randomized studies with more than 900 patients and convincingly demonstrated that stentless AVR does offer a lower valve pressure gradient and more rapid LV mass regression at 6 months than stented AVR, (at the expense of a longer aortic cross-clamp time).
A meaningful clinical comparison of the hemodynamic performance between stentless and stented AVR is based on the assumption that both achieve an in vivo effective orifice area (EOA) inline with in vitro measurements. However, the in vivo EOA for stentless AVR was often only 60% of its in vitro measurement. The corresponding figure for stented AVR was greater than 90% [2]. The stentless EOA discrepancy is mainly due to requiring a semi-reconstructive procedure. When the implantation is well optimized in the native aortic root, the stentless valve EOA can be as much as 90% of in vitro EOA [3]. Therefore the significant, but modest, in vivo hemodynamic advantage of the stentless AVR demonstrated in Kunadian and colleagues’ [1] meta-analysis was achieved despite the in vivo under performance of the stentless valve against its stented competitor. If the stentless AVR clinical trials necessitated the recruitment of less experienced surgeons to boost implant numbers, their findings may reflect the performance of the surgeon rather than that of the stentless prosthesis.
The changes in LV mass index after stentles and stented AVR is an important comparative physiological end point, but this approach requires significant pre-existing and reversible LV hypertrophy (LVH) caused by aortic valve disease, and it requires the absence of confounding diseases that cause LVH. As the majority of LVH regression takes place in the first 6 months after surgery, the favorable effects of stentless AVR should be evident at this time point. This indeed was the case in this meta-analysis. Beyond 6 months hypertension, atrial fibrillation, cardiac dysfunction, and associated medical treatments will play an increasing role in determining residual LVH [4], and these factors probably explain the long-term survival advantage of stentless AVR being more evident in patients younger than 70 years of age in comparison with those older than 70 years [5].
Given the impact of surgeon’s expertise on stentless valve hemodynamics and of the patient’s factors on LVH regression after AVR, the individual randomized clinical trial in elderly AVR patients requires more thoughtful interpretation. To this end, the current meta-analysis has offered an important complementary approach. Its findings should be commended for the further development of both surgical expertise and user-friendly prosthesis for the stentless AVR.
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