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Book Review: Stentless Bioprosthesis

An initial perusal of the table of contents clearly shows that at the present time, work on stentless valves is practically centered on the aortic valve. The first two sections report isolated and still rather esoteric papers on monocusps for right ventricular reconstruction, Ross procedure on a previous arterial switch, and mitral replacement with xenogeneic mitral and pericardial stentless valves. The bulk of the information corresponds to what most readers would expect from the title, that is the porcine aortic stentless bioprosthesis. The new so-called “stentless bioprosthesis” is the latest development in the already long history of tissue valve replacement. This has erupted into the market with force and has been received with enthusiasm due to several factors. In the first place, it is because of the recent return of interest in tissue valves among the surgical community. This is due to the shift towards a progressively older patient population with greater problems of permanent anticoagulation and the excellent durability of the standard bioprosthesis in these elderly patients. Secondly, better cardiopulmonary and myocardial protection techniques have reduced the anxiety attached to longer and more complex procedures. Increased familiarity with aortic root replacement and larger experience with stentless homografts have resulted in more standardized implantation techniques. Thirdly, the realization that residual gradients, obviously more significant in small aortic annuli, negatively affect the long-term outcome of valve replacements. This problem which might demand root enlargement procedures, offsets the technical simplicity of a standard prosthetic replacement. Finally, although not yet proven, it is expected that the absence of a stent should reduce mechanical stress and, therefore, increase the durability of the glutaraldehyde-treated porcine aortic valve. It has been pointed out that the original porcine valves placed in the 1960s, were all stentless and that the advent of the stented bioprosthesis was universally welcomed as a positive development. However, it has to be remembered that these early porcine valves were not glutaraldehyde-treated and, therefore, had handling characteristics similar to homografts. Present-day stentless valves are much stiffer because they are cross-linked and reinforced with Dacron or pericardium, maintaining their shape during implantation.