A clampless and sutureless aorto-prosthetic end-to-side anastomotic device: an experimental study.

OBJECTIVES: A feasibility study. METHODS: Eight pigs (all females; mean weight: 29 kg) underwent a conventional transperitoneal aortic approach with implantation of an aorto-prosthetic end-to-side anastomosis using a Clampless device and deployment of a 5-mm polytetrafluoroethylene (PTFE) graft. After proximal ligature, a conventional end-to-end anastomosis was then performed between the graft and the left iliac artery. RESULTS: The first pig died during the procedure due to graft misplacement. The seven other procedures were successful with a mean operative and anastomosis time of 101 min (range: 81-115 min) and 3.35 min (range: 2.25-4.25 min), respectively; mean blood loss was 152 ml (range: 30-235 ml). Another pig with a patent graft died at day 4 as a result of a severe unrelated pneumonopathy. The angiogram performed during the procedure and before sacrifice, at 2 (n=2), 4 (n=2) and 6 weeks (n=2), showed no graft stenosis or thrombosis. Microscopic examination revealed a tissue covering the intraluminal stent, which evolved over time, with no visible endothelial proliferation or inflammation. CONCLUSION: An aorto-prosthetic anastomosis can be performed safely and efficiently with our new clampless and sutureless device. The next step will be a laparoscopic Clampless implantation.

Evaluation of a new vascular suture system for aortic laparoscopic surgery: an experimental study on pigs and cadavers.

OBJECTIVES: The aim of this study was to assess the feasibility and efficacy of a new laparoscopic vascular suturing device. METHODS: Animal study: six pigs underwent surgery using a retroperitoneal laparoscopic approach. Aorto-prosthetic side-to-end and end-to-end anastomoses were performed laparoscopically on each pig using SuDyn. Clamping and anastomosis times, as well as the properties of the anastomoses, were recorded. Study on cadavers: four aorto-prosthetic end-to-end anastomoses were performed using the direct transperitoneal laparoscopic approach to assess the feasibility of the SuDyn device on atherosclerotic aortas. RESULTS: Animal study: No pigs died and 12 patent and impermeable anastomoses were obtained. Mean anastomosis time was 38(+/-8)min for end-to-side anastomoses and 37(+/-5)min for end-to-end anastomoses. Study on cadavers: Totally laparoscopic anastomoses were performed in 4 human cadavers with a mean anastomosis time of 37(+/-3)min. CONCLUSIONS: SuDyn makes laparoscopic aorto-prosthetic anastomoses easier to perform, produces good results and does not require a learning curve.

Are laparoscopic staplers effective for ligation of large intraabdominal arteries?

OBJECTIVES: To evaluate ligation of aortoiliac arteries with laparoscopic staplers in order to develop specifically designed staplers. METHODS: Cadaveric study. Seven human cadaver aortas were stapled using EndoGIA60 staplers. Efficiency was evaluated macroscopically and on a hydrodynamic bench. Clinical study. Twelve patients had ligation of 14 large abdominal arteries (aorta: nine, iliac artery: four, hepatic artery: one) using a laparoscopic stapler. Stapling efficiency was judged on peroperative clinical and postoperative CT scan criteria. RESULTS: Cadaveric study. Stapling was performed perfectly on four moderately calcified aortas, without leakage with a pulsatile pressure of >250 mmHg. For three aortas with severe calcification, stapling was not efficient and major leakage occurred. Clinical study. Stapling appeared clinically efficient on all arteries but one aorta: this severely calcified aorta was ligated conventionally. The staplers are not easy to use due to their shape and their lack of articulation. After a mean follow-up of 31.3 months, all the other stapled arteries were effectively ligated. CONCLUSION: The commercially available staplers can be used securely on moderately calcified arteries but stapling of severely calcified arteries should be avoided. These devices should be redesigned to facilitate their use in vascular surgery.

[Prostheto-prosthetic and aorto-prosthetic anastomosis using stents, threads, clips and staples. In vitro comparative study]. / Anastomoses prothéto-prothétiques et aorto-prothétiques par stents, fils de suture, clips et agrafes. Etude 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.

In-vitro measurements of the regurgitation of mechanical mitral heart valve prostheses in case of atrial fibrillation.

BACKGROUND AND AIM OF THE STUDY: The characterization of heart valve prostheses requires regurgitation tests to be conducted in pulsatile flow. Although tests are generally conducted in accordance with hemodynamic conditions of a healthy young man, heart valve implantation is often associated with other pathology, such as atrial fibrillation. To run more realistic trials, four mechanical heart valve prostheses were tested with, and then without, atrial contraction. METHODS: The dual activation simulator (DAS) allow simulation of physiologically normal and pathological flows through the mitral valve. The DAS comprises silicon-based cavities, is activated by pumps, and was equipped successively with monoleaflet (Björk-Shiley, Medtronic Hall) and bileaflet (St. Jude Medical, CarboMedics) valves. Each valve (mitral, size 27 mm) was tested under two conditions (with and without atrial contraction) at a mean flow rate of 3 l/min of glycerol/water solution (analog blood viscosity). RESULTS: Leakage volumes were of the same magnitude as the precision of the instruments. Respectively, closing volumes increased from normal conditions to atrial fibrillation from 3.2 to 5.1 ml for Björk-Shiley, from 4.6 to 6.3 ml for Medtronic Hall, from 5 to 6.6 ml for St. Jude Medical, and from 5.2 to 5.4 ml for CarboMedics. The standard deviation was below the precision of measurements (+/- 0.5 ml). CONCLUSION: Without atrial contraction, the valves seemed to be closed by backward flow only, thus confirming earlier reports. This study showed that different heart valves behave differently in pathological situations with regard to their design; this must be considered when selecting a valve for implantation.

A new dual activation simulator of the left heart that reproduces physiological and pathological conditions.

Heart valve replacements are often associated with cardiac pathologies, but valvular prostheses are still tested in vitro under the same physiological conditions as for a healthy young man. Therefore a new mock circulatory system of the left heart, the dual activation simulator (DAS), has been built. The DAS allows atrial and ventricular dynamics to be controlled with pumps that activate anatomically shaped silicon models of the cavities. The mitral flow is a two-peak waveform. The E/A ratio can be changed, and the A-wave can be suppressed to simulate, for instance, atrial fibrillation. The cardiac rhythm and the mean flow-rate can be changed at will. The ability of the DAS to reproduce physiological flow is assessed by computation of the aortic input impedance and by harmonic analysis of left ventricular and atrial pressures. It allows the behaviour of valve prostheses to be studied in various conditions of concern to clinicians and can be a useful tool for engineers to improve valve prostheses or validate diagnostic tools such as 3D colour Doppler. The DAS and its capacities are described.

Elastic recoil of coronary stents: a comparative analysis.

Minimum elastic recoil (ER) has became an essential feature of new coronary stents when deployed in artheromatous lesions of various morphologies. The ER of coronary stent might be an important component of 6-month restenosis rate by minimizing the luminal loss. We evaluated the intrinsic ER of 23 coronary stents with a mechanical test bench. The amount of ER for one size of stent (3.0 mm) was quantified using a 3D optical contactless machine (Smartscope MVP, Rochester, NY). The stents were expanded on their own balloon for the precrimped stents; the uncrimped stents were expended using identical 3.0-mm balloons. Two types of measurements were done without exterior stress and with a 0.2-bar exterior stress, directly on the stent at the end of balloon expansion, immediately after balloon deflation, and then 30 min, 60 min, and 120 min after. ER ranged from 1.54%+/-0.81% (Bestent BES 15) to 16.51%+/-2.89% (Paragon stent) without stress (P<0.01) and from 2.35%+/-1.14% (Bestent BES 15) to 18.34%+/-2.41% (Cook GR2) under 0.2-bar pressure (P<0.0001). Furthermore, there was a significant reduction between the mean result of tubular stents (TS) and coil stents (CS). The results of in vitro mechanical tests may confirm strongly the interest of a minimum ER in the prevention of the 6-month restenosis.

Radial force of coronary stents: a comparative analysis.

High radial force has become an essential feature of new coronary stents. These stents are expected to exhibit sufficient radial force and minimum radial recoil when deployed in atheromatous lesions of various morphologies. The aim of this study was to compare the radial force of 17 coronary stents in vitro (Anglodynamics, ACS Multilink, AVE Micro II and GFX, Bard XT, Biocompatibles PC, Cook GR II, Cordis Crossflex, Hexacath Freedom, Johnson & Johnson PS 153'PS 154, and Crown, Medtronic Wiktor and BeStent BEL-15, Saint-Come SC 1616, Scimed Nir 7 and 9). Two in vitro mechanical tests were performed to assess the stent radial force. The first test measured the deformation of coronary stents in a V-stand by using a deformation controlled by a dynamometer based on a longitudinal generatrix. The precision was of 1 micron. This comparative test highlighted the appreciable variation in behavior of the range of tested stents in terms of resistance to local compression. The line graphs obtained show a very small (and in some cases nonexistent) purely elastic behavior area in the stents, with this result reflecting a small (<0.4 Newtons) range of forces applied to all stents. Above this value, the stents did not return to their size before compression and the line graph remains approximately linear for a long period. It was therefore possible to distinguish between two families of stents on the basis of the presence or absence of this elastic area. In the second test, the stent was deployed in a 3.0-mm elastic tube and a pressure gradient created between the interior and exterior of the tube. The precision was of 50 microns. A typical line graph of the pressure-diameter relationship was recognizable for a given stent. No difference in behavior between the different coronary stents was noted up to 0.3 x 10(5) Pa; subsequently, after 0.3 x 10(5) Pa, sizable deformation differences were visible between the least resistant stent, the BeStent BEL-15, and the most resistant stent, the Crossflex.

Ventricular flow dynamic past bileaflet prosthetic heart valves.

To characterise hydrodynamic properties of prosthetic heart valves in mitral position, ultrasonic velocity measurements were performed using a cardiovascular simulator. A Duromedics and a Saint-Jude Medical bileaflet heart valve were tested. The Saint-Jude valve was oriented first in an anatomical position, i.e. the tilt axis parallel to the septal wall, and then in an anti-anatomical position. In the anti-anatomical position, from mid diastole to mid systole, two contrarotative vortices are generated in the ventricle by the interaction between the flow directed by the leaflets downstream from the lateral orifices and the ventricular wall motions. In the anatomical position, the mitral flow penetrates the ventricle principally through the lateral orifice proximal to the septal wall, due to the vortex in the atrial chamber. The mitral inflow then circulates along the septal wall to the apex, and produces a large ventricular vortex during systole. In the anatomical position, the Saint-Jude thus provides a better ventricular washout during this phase. The mitral inflow through the Duromedics in the anti-anatomical position produces two contrarotative vortices in the ventricle, but in the opposite sense than downstream the Saint-Jude valve; the flows that penetrate through the lateral orifices are directed to the ventricular walls and then recirculate to the centre of the ventricle, providing a very fluctuating flow near the apex. Thus, a slight difference in valve design produces a significant difference in the ventricular flow fields.

Near velocity field downstream prosthetic valves in aortic position.

Using a cardiovascular simulator to duplicate in vitro the flow conditions through valves in aortic position, bidimensional velocity maps very near the valve are reconstructed, from an ultrasonic 8 Mhz doppler system, in an elastic model of the ascending aortic arch. Three mechanical heart valves representative of the different types of commercial models (a tilting disc, a ball in cage and a two-leaflet valve) and a new bileaflet prototype were investigated. From examination of the velocity field, it is possible to define the main characteristics of the valve wake and to observe the development of negative velocities associated with regurgitant flows. From a comparison with tests in rigid tubes, the role played by the arch elasticity is analysed.