Anastomoses prothéto-prothétiques et aorto-prothétiques par stents, fils de suture, clips et agrafes : étude comparative sur banc d'essai

OBJECTIVE: --To evaluate mechanical strength of new potential systems of vascular prostheses anastomosis versus usual suture (4.0 yarn), --To advance objective quantified data in order to establish the specifications of a new quick and reliable mechanical anastomosis device for laparoscopic surgery. MATERIAL AND METHODS: Two experimental studies were conducted in order to quantify the mechanical resistance of anastomoses between two Dacron vascular prostheses and anastomoses between one Dacron vascular prosthesis and one cadaver abdominal aorta segment. Existing materials, which have generally used for other types of surgery, were applied for these studies (clips, staples, stents). These systems of anastomosis were compared to usual suture, used as reference. RESULTS: The mechanical strength of an anastomosis between two Dacron vascular prostheses performed with staples or the same number of stitches is of equivalent magnitude. Anastomoses made with clips or stent are ten to fifteen times weaker than those made with stitches. We did not succeed in performing an anastomosis with staples on cadaver aorta segments because aorta segments tear when staples are applied. In the experiments with a hand-sewn graft, the aorta always tor before the suture, without breakage of the suture. CONCLUSION: From these in vitro trials, we can advance that a continuous suture is probably far too resistant in relation to the aorta own resistance. As we do not know accurately the physiologic strength applied to a vascular prosthesis in vivo, one acceptance criterion from a safety point of view for a new anastomosis system must be that its strength will be equal to the well-proven continuous suture (greater than 150 N) or to the aorta breaking point (between 100 and 160 N). From that point of view, anastomoses performed with clips or a stent are not convenient, unless special clips or stents can be developed for this application. The mechanical strength is of staples sufficient but their design has to be adapted to this particular type of anastomosis

Laparoscopic aortic surgery : recent development in instrumentation

In addition to conventional and endovascular techniques, laparoscopic surgery is becoming a third way to treat patients with aortoiliac occlusive or aneurysmal diseases. Several different laparoscopic techniques are available, but most authors are stressing the need for development of specific laparoscopic aortic instruments, to decrease the operative and clamping times and reduce the learning curve. Our experience of more than 150 patients who underwent a laparoscopic abdominal or thoracic aortic reconstruction, has lead us to imagine the instruments that may facilitate these procedures, and then to create a society with Vascular Surgeons and Biomedical Engineers, called PROTOMED, which may conceive, develop, and test new medical instruments. This Chapter presents an overview of what is available currently, such as laparoscopic aortic clamps or laparoscopic intestinal retractors; others are in the experimental stage, such as laparoscopic aortic staplers, anastomotic devices, and robotic surgical systems. This important technologic challenge should lead to 2 major orientations: development of qualitative in vitro and in vivo experiments to test these new products, and training courses to teach their use. Minimally aggressive techniques are well adapted to a western population growing older and has access to constantly improving medical care; however, only specific and ergonomic instruments will allow these new techniques to be widely embraced by the vascular surgical community

Laparoscopic aortic surgery : recent development in instrumentation

In addition to conventional and endovascular techniques, laparoscopic surgery is becoming a third way to treat patients with aortoiliac occlusive or aneurysmal diseases. Several different laparoscopic techniques are available, but most authors are stressing the need for development of specific laparoscopic aortic instruments, to decrease the operative and clamping times and reduce the learning curve. Our experience of more than 150 patients who underwent a laparoscopic abdominal or thoracic aortic reconstruction, has lead us to imagine the instruments that may facilitate these procedures, and then to create a society with Vascular Surgeons and Biomedical Engineers, called PROTOMED, which may conceive, develop, and test new medical instruments. This Chapter presents an overview of what is available currently, such as laparoscopic aortic clamps or laparoscopic intestinal retractors; others are in the experimental stage, such as laparoscopic aortic staplers, anastomotic devices, and robotic surgical systems. This important technologic challenge should lead to 2 major orientations: development of qualitative in vitro and in vivo experiments to test these new products, and training courses to teach their use. Minimally aggressive techniques are well adapted to a western population growing older and has access to constantly improving medical care; however, only specific and ergonomic instruments will allow these new techniques to be widely embraced by the vascular surgical community

Assessment of the trackability, flexibility, and conformability of coronary stents: A comparative analysis

The efficacy and safety of coronary stent implantation depend on the mechanical features of these devices when deployed in atheromatous lesions of various morphologies. We evaluated the trackability, flexibility, and conformability of 17 coronary stents using specific mechanical bench tests. The quantifications used a dynamometer for assessment of trackability (maximal strength) and flexibility (stiffness) and a 3D optical gauging machine for assessment of conformability (distance between stent and arterial wall in a curvature). The maximal strength (measuring the trackability) ranged respectively from 0.24 ± 0.06 and 0.38 ± 0.03 N (Seaquest) to 1.31 ± 0.42 and 1.34 ± 0.35 N (Carbostent), concerning respectively curvatures of 90° (P < 0.0001) and 135° (P < 0.0001). The stiffness (measuring the flexibility) ranged from 0.53 ± 0.16 (Seaquest) to 1.28 ± 0.10 N/mm (NIR Royal; P < 0.0001). The mean distance between stent and external curvature (external conformability) ranged from 0.15 ± 0.06 mm (S7) to 0.57 ± 0.4 mm (NIR Royal; P < 0.0001). The mean distance between stent and internal curve (internal conformability) ranged from 0.26 ± 0.13 (S7) to 0.44 ± 0.12 mm (S670; P < 0.0001). These results may influence the choice of a particular stent adapted to a specific coronary anatomy

Independent contribution of left ventricular ejection time to the mean gradient in aortic stenosis

BACKGROUND AND AIMS OF THE STUDY : Transvalvular mean pressure gradients (MPG) are important in the evaluation of aortic stenosis, but surprisingly they often differ in patients having similar valve effective orifice area (EOA) and stroke volume (SV). The study aim was to determine if these differences could be explained by variations in left ventricular ejection time (LVET). METHODS : A pulse duplicator system with a constant SV of 75 ml and incremental increases of LVET from 250 to 450 ms was used to measure MPG by Doppler echocardiography in three fixed stenoses (0.5, 1.0 and 1.5 cm2). The same variables were also measured at rest in 192 patients with isolated aortic stenosis (EOA <1.5 cm2) as well as during stress in a subgroup of 24 patients. RESULTS : In vitro, the increase in LVET produced marked decreases of MPG ranging from -40 mmHg (-45%) for the 0.5-cm2 stenosis to -22 mmHg (-61%) for the 1.5-cm2 stenosis. In vivo, MPG measured by Doppler correlated strongly (R2 = 0.83) with the MPG predicted by the formula: MPGpred [SV/(50xEOAxLVET)]2, and on this basis the relative contributions of EOA, SV and LVET to the variance of MPG were found to be 36, 34 and 13%, respectively. During stress, the contribution of LVET to the increase in MPG was variable, but was sometimes as important as that of SV. CONCLUSION : LVET may significantly and independently influence MPG in aortic stenosis. Clinically, variations of up to 15 mmHg in MPG may be observed uniquely on the basis of a change in duration of LVET, and hence the MPG cannot be used as a stand-alone parameter for serial evaluations or for comparisons of aortic stenosis severity between patients. A correction of MPG for LVET (in ms) such as MPGc = MPGx(LVET/300)2 might be helpful for rendering comparisons of MPG more meaningful in patients with aortic stenosis