Carlos Mg Duran

Aortic and pulmonary root: are their dynamics similar?

OBJECTIVESnThe long-term behavior of the pulmonary autograft in the aortic position (Ross procedure) remains uncertain. Using three-dimensional (3D) sonomicrometry (200 Hz) we compared the dynamics of the aortic and pulmonary roots.nnnMETHODSnTwenty-four crystals were implanted in each aortic (eight sheep) and pulmonary roots (six sheep) at: base (3 x 2), commissures (3 x 2), sinotubular junction (3 x 2), ascending aorta (3) and pulmonary trunk (3). Under stable hemodynamic conditions, geometric changes were time-related to left ventricular pressure (LV) and aortic pressure.nnnRESULTSnThe expansion of the aortic root is twice that of the pulmonary root. During the cardiac cycle, the aortic root volume increased by 37.7 +/- 2.7% (mean +/- SEM) versus 20.9 +/- 1.0% for the pulmonary root. Both were cone-shaped at end diastole. Because expansion at commissures was twice that of the base, both roots became more cylindrical during ejection. Although both roots started to expand prior to ejection and reached maximal expansion during the first third of ejection, the commissural and sinotubular junction dynamics were different in each root. While in the aortic root, expansion at commissural and sinotubular junction levels was significantly different (63.7 +/- 3.6% versus 37.0 +/- 2.1%), in the pulmonary root, they were similar (29.0 +/- 1.3% versus 27.7 +/- 1.4%). Expansion of the three sinuses was also different (P<0.001). In the aortic root: the right expanded more than the left and more than the non-coronary sinus. In the pulmonary root: the right sinus expanded more than the anterior more than the left.nnnCONCLUSIONSnDynamic differences might explain the global pulmonary root dilatation when subjected to systemic pressure, particularly at the level of the sinotubular junction which might result in the autograft failure. Differences in the asymmetrical expansion of the aortic and pulmonary roots should be considered for the implantation of the pulmonary autograft in the most physiological position.

Behavior of vital and killed autologous pericardium in the descending aorta of sheep

OBJECTIVESnCardiovascular implants of fresh autologous pericardium produced mixed results including fibrosis with retraction or thinning and dilatation. The reasons for these differences are unknown but may involve activation of cells intrinsic to the tissue implant. To better understand the behavior of autologous pericardial implants, we studied the outcomes of vital pericardium (fresh) versus ethanol-killed pericardium.nnnMETHODSnFresh and ethanol-killed autologous pericardium was transplanted as a patch, a conduit, or a rectangular flap bisecting the lumen in the descending aorta of sheep. The implants, recovered at 1, 5, 10, 15, and 30 days, were evaluated macroscopically and microscopically and by immunohistologic studies.nnnRESULTSnFresh implants showed good preservation with fibrin deposition on day 15. Microscopically, cells positive for alpha-actin and von Willebrand-related antigen appeared in the fibrin by day 10. By day 30 the flap was fibrotic and retracted whereas the patch and conduit retained their original appearance on the luminal aspect. An endothelium-like layer expressing von Willebrand-related antigen was present in the patch and conduit but absent in the flap. In contrast, the ethanol-killed implants were free of fibrin by day 10. By day 30, there were no signs of fibrosis or retraction, and a surface layer of cells expressing von Willebrand-related antigen, characteristic of endothelial cells, was present on all implants. All ethanol-killed implants were repopulated by host cells.nnnCONCLUSIONnThe transluminal flap is an interesting model for studying the behavior of intraluminal autologous pericardial cardiovascular implants. Killing of the pericardial implants alleviated the fibrosis and tissue retraction observed with fresh flap implants.

Standards and Concepts in Valve Surgery

INTRODUCTION With the advent of open heart surgery it has been possible to actively fight valvular diseases. Before World War II there were some reports of operations on the heart, but these operations were rare and anecdotal. Closed techniques were performed occasionally in mitral surgery after World War II. After 1952, a major breakthrough occurred with the introduction of artificial valves and coronary artery bypass graft (CABG) surgery for open heart surgery.

Book Review: Stentless BioprosthesisStentless Bioprosthesis2nd Edition, Edited by HuysmansHans AMD, PhD DavidTirone E MD, FRCS(c), FACS WestabyStephen BSc, FRCS, MD ISBN 1-899066-18-7 • List Price £95/US

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.

150 • Isis Medical Media, Oxford, UK

A simple device for in vitro assessment of aortic surgery on an isolated heart or aortic root specimen is described. This device was designed as a simple tool to provide surgeons with immediate and direct visual feedback on the results of a procedure performed on the aortic valve in an isolated cardiac specimen. The objectives were to assess the duration of learning new aortic surgical procedures and to instill a greater sense of confidence to the surgeon prior to operating on a patient. Free-hand pericardial aortic valve reconstructions were performed on 9 pig hearts and 5 human homografts, which were tested with this device. In the pig, valve reconstruction was tested using the whole heart as well as the isolated aortic root. Detailed qualitative and quantitative assessments of the performance of the reconstructed aortic valve were possible using this device.