Clampless 2 Device: Experimental Study of a Lateral Aorto-Prosthetic Anastomosic Device Without Clamping or Suturing.

BACKGROUND: To offer an alternative to conventional techniques of lateral prosthetic anastomosis on arteries which require a long training, and impose an extensive open surgery, we are proposing the clampless 2 device (C2D) implanted by a simple arterial puncture and allows a lateral implantation of a polytetrafluoroethylene (PTFE) vascular graft in an artery, without arterial clamping or suture. METHODS: C2D is a "T" shaped 25-mm long and 8-mm diameter Nitinol stent with a 6-mm PTFE graft prosthesis mounted laterally on the stent, and implanted in an artery, via a 21-French sheath, and a compliant balloon inflation. In vitro testing of the C2D was first performed on a bench including a segment of a 7-mm internal diameter pig abdominal aorta. A series of 5 consecutive C2D implantation was analyzed with evaluation of the implantation time and the fluid losses at a fluid pressure of 80 and 150 mm Hg. The C2D implantation was finally controlled by angioscopy. An aorto-iliac bypass was then secondly performed on 8 living sows, with a side-to-end C2D implantation in the infrarenal abdominal aorta, followed by a conventional end-to-end prosthetic left iliac trunk anastomosis. The C2D and distal conventional anastomotic times were evaluated, as well as the total operative time and blood loss. A postoperative angiogram was systematically performed. RESULTS: The C2D was successfully implanted in all 5 in vitro tests, with an average implantation time of 2'58 (range: 2'25-3'22). The mean value of fluid losses was 84 ml (range: 67-94 ml), with no fluid leakage occurring at 80- and 150-mm Hg pressure. All anastomoses were patent after macroscopic study by angioscopy with a perfect application of the stent in the aortic wall. In 8 living sows (mean weight: 42 kg, 37-50 kg), an aorto-left iliac bypass was successfully implanted in all cases, with a total mean procedure time of 101 min (range: 90-130 min), and an average fluid loss of 77 ml (range:20-120 ml). The mean implantation time was 4'39 (range 3'29-5'52) for C2D and 16 min (range 12-17 min) to perform the conventional distal prosthetic-iliac anastomosis. Systematic arteriographic and angioscopy control showed perfect patency of the C2D implantations. CONCLUSIONS: Preliminary in vitro and acute in vivo testing of C2D implantation show good early results, allowing further long-lasting pig experiments on the way to human homologation.

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.

In vitro atrial flow dynamics: normal conditions versus atrial fibrillation.

AIMS: The flow dynamics in the atrium is poorly described. The reasons are principally due to the complicated geometry of the cavity and its contractility. The present in vitro study focuses on the description of the flow in the left atrium in normal conditions (NC) and in atrial fibrillation (AF). The final objective is to give leads to understand, from the hemodynamic point of view, complications in case of AF. METHODS AND RESULTS: An atrio-ventricular dual activation system is used to simulate physiological flow in the left atrium. The cavities are compliant and transparent. Velocity measurements are performed with Particle Image Velocimetry. Systolic peak of the pulmonary venous flow is about 0.4 m s(-1) and diastolic peak 0.6 m s(-1) in magnitude. Vortices appear during diastasis and systole and are of normal size and duration. In early and late diastole, the ventricular filling (in NC and AF) and the atrial contraction (in NC only) create a characteristic flow pattern that consists in directed flow towards the mitral valve. In AF an increased resident time (500 ms versus 300 ms) and a slow helical flow pattern (about 0.1 m s(-1)), similar to what is measured using ultrasound echocardiography are observed. CONCLUSION: This study uses atrial flow dynamics description to help understand why thromboembolisms occur in AF.

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.