Jean-Pierre Bossavy

Early Potent Antithrombotic Effect With Combined Aspirin and a Loading Dose of Clopidogrel on Experimental Arterial Thrombogenesis in Humans

BACKGROUND We conducted a double-blind, randomized, crossover study to assess the antithrombotic effects of the combination of aspirin (acetylsalicylic acid, ASA) and clopidogrel, with or without a loading dose, versus ASA alone in a model of arterial thrombosis in humans. METHODS AND RESULTS Eighteen male volunteers received the following 3 regimens for 10 days separated by a 1-month period: (1) 325 mg ASA daily, (2) 325 mg ASA+75 mg clopidogrel daily, (3) 325 mg ASA daily+300-mg clopidogrel loading dose on day 1 and +75 mg clopidogrel per day on days 2 to 10. The antithrombotic effect was measured 1.5, 6, and 24 hours after drug intake on day 1 and 6 hours after drug intake on day 10. Arterial thrombus formation was induced ex vivo by exposing a collagen-coated coverslip in a parallel-plate perfusion chamber to native blood for 3 minutes at an arterial wall shear rate. Without a loading dose, clopidogrel+ASA developed an antithrombotic effect within 6 hours after the first intake. It was superior to that produced by ASA, but it was moderate (P</=0.03). However, with the loading dose, the antithrombotic effect of clopidogrel+ASA appeared within 90 minutes, and after 6 hours it was comparable to that on day 10. On day 10, clopidogrel+ASA decreased platelet thrombus formation by approximately 70%, and the effect was significantly more potent than that produced by ASA alone (P<0.001). CONCLUSIONS This study confirms the synergistic antithrombotic effects of a combined ASA and clopidogrel therapy and shows the early benefit obtained with a loading dose of clopidogrel.

The Thrombomodulin/Protein C/Protein S Anticoagulant Pathway Modulates the Thrombogenic Properties of the Normal Resting and Stimulated Endothelium

We investigated the role of the thrombomodulin (TM/protein C/protein S anticoagulant pathway in modulating the thrombogenic properties of the endothelium. Endothelial cells (ECs) were placed in parallel-plate flow chambers and exposed to nonanticoagulated human blood at a venous wall shear rate (50 s-1). Fibrin deposition on resting ECs treated with a control IgG1 was negligible. In contrast, a significant amount of fibrin deposited when TM expression was specifically suppressed by > 95% by preincubating ECs with an anti-TM IgG1. Similarly, fibrin deposited on interleukin 1-stimulated ECs, but the fibrin deposition was further increased threefold with anti-TM IgG1. Comparable results were found when ECs were perfused at 650 s-1. When TM surface activity was enhanced by 150% by treating ECs with active phorbol ester (4-phorbol 12-myristate 13-acetate; PMA), the deposition of fibrin was 30% lower than on ECs not pretreated with PMA. Finally, fibrin deposition on stimulated ECs was significantly higher in 11 untreated patients with well-characterized deficiencies of protein C or S or heterozygous factor V Leiden mutation than in 11 healthy individuals, and it was significantly correlated to basal plasma levels of thrombin-antithrombin complexes. Thus, this study underlines the central role of the TM/protein C/protein S pathway in modulating the thrombogenic status of resting and stimulated ECs and indicates that basal coagulation system markers may be helpful in monitoring patients presenting a disorder of this anticoagulant pathway.

Comparison of the Antithrombotic Effect of PEG-Hirudin and Heparin in a Human Ex Vivo Model of Arterial Thrombosis

Polyethylene glycol (PEG)-hirudin is a derivative of hirudin with a long plasma half-life. We have compared the efficacy of PEG-hirudin with unfractionated heparin (UH) in preventing arterial thrombosis. Arterial thrombus formation was induced ex vivo in 12 healthy human volunteers by exposing a tissue factor-coated coverslip positioned in a parallel-plate perfusion chamber to flowing nonanticoagulated human blood drawn directly from an antecubital vein at an arterial wall shear rate of 2600 s-1 for 3.5 minutes. PEG-hirudin, UH, or saline (as control) were administered ex vivo through a heparin-coated mixing device positioned proximal to the perfusion chamber. Platelet and fibrin deposition was quantified by immunoenzymatic measure of the P-selectin and D-dimer content of dissolved plasmin-digested thrombi, respectively. UH was administered to a plasma concentration of 0.35 IU/mL. This concentration prolonged the activated partial thromboplastin time from 32+/-1 seconds to 79+/-4 seconds (P<0.01). UH did not significantly prevent platelet deposition. However, fibrin deposition was reduced by 39% (P<0.05). PEG-hirudin in plasma concentrations of 0.5, 2.5, and 5 microg/mL prolonged the activated partial thromboplastin time to 48+/-2, 87+/-4, and 118+/-4 seconds, respectively. In contrast to UH, PEG-hirudin prevented both platelet and fibrin deposition in a dose-dependent manner with a >80% reduction at 5 microg/mL (P<0.01). Furthermore, the plasma level of PEG-hirudin required to significantly prevent fibrin deposition (0.5 microg/mL) corresponded to a much shorter prolongation of activated partial thromboplastin time (48+/-2 seconds) than that needed for UH (79+/-4 seconds). Thus, our results are compatible with the view that thrombin is greatly involved in recruitment of platelets in evolving thrombi, and that PEG-hirudin is an effective agent for preventing arterial thrombosis in a human ex vivo experimental model.

Abdominal Infectious Aortitis Caused by Streptococcus pneumoniae: A Case Report and Literature Review

We report a case of a 75-year-old man who had been complaining of fever and pelvic pain for 3 weeks. First angio-computed tomography (CT) characteristics and blood culture led to suspicion of a pneumococcal-infected aortic aneurysm, which however was not confirmed by the surgeon. The abdominal infectious aortitis caused by Streptococcus pneumoniae was affirmed by a second angio-CT performed 7 days later. Without further delay, the patient underwent surgery for resection of mycotic aneurysm and in situ reconstruction with aortobiiliac homograft, in association with antibiotics. He died 10 days after the surgery as a result of severe sepsis in a polyvalent intensive care unit. This case report highlights the severity of this pathology. We reviewed the relevant literature related to Streptococcal pneumoniae mycotic aneurysm located in the abdominal aorta, including 29 more cases. Various microorganisms have already been associated with mycotic aneurysms, including S pneumoniae. Infectious aortitis remains a rare disease. It is extremely important to establish an early diagnosis but it may be delayed because clinical manifestations are usually nonspecific. However, if left untreated it is always lethal. Antibiotic in combination with complete surgical excision of the infected aorta is the treatment of reference. This therapeutic association dramatically improved patient survival.

Antithrombotic Efficacy of the Vitamin K Antagonist Fluindione in a Human Ex Vivo Model of Arterial Thrombosis Effect of Anticoagulation Level and Combination Therapy With Aspirin

Thrombin is a main mediator of arterial thrombus formation, and its inhibition is an important antithrombotic strategy. However, the place of vitamin K antagonists among the different therapeutic strategies for preventing arterial thrombus formation is still debated. We studied the antithrombotic efficacy of the vitamin K antagonist fluindione in a human ex vivo model of arterial thrombosis and determined whether aspirin enhances fluindione efficacy. Ten healthy male volunteers were randomly assigned to receive fluindione, alone or in combination with aspirin (325 mg/d). Fluindione was given at increasing doses to give a stable international normalized ratio (INR) between 1.5 and 2.0 and between 2.1 and 3.0. We induced arterial thrombus formation ex vivo by exposing collagen- or tissue factor (TF)-coated coverslips in a parallel-plate perfusion chamber to native blood for 3 minutes at an arterial wall shear rate of 2600 s(-1). Platelet and fibrin deposition were measured by immunoenzymatic methods. Fluindione inhibited thrombus formation on TF-coated coverslips in a dose-dependent manner by 50% and 80% at INR 1.5 to 2.0 and INR 2.1 to 3.0, respectively (P<0.05). Fluindione in combination with aspirin inhibited TF-induced thrombus formation in a comparable manner. Collagen-induced thrombus formation was not reduced in subjects treated by fluindione. It was reduced by 50% to 60% in those treated with fluindione plus aspirin, regardless of the level of anticoagulation (P<0.05). Thus, the effectiveness of fluindione for preventing arterial thrombosis is dependent on the nature of the thrombogenic trigger. Fluindione is very effective in preventing TF- but not collagen-triggered thrombus formation. Aspirin enhances the antithrombotic effectiveness of fluindione, because combined treatment interrupts both TF- and collagen-induced thrombus formation.

Experimental study of a novel mechanical connector for sutureless open arterial anastomosis

OBJECTIVES This study assessed the feasibility and efficacy of a new sutureless connector for end-to-end arterial anastomosis. METHODS The anastomotic device is a connector consisting of a bare-metal stent with spikes covering its outer surface, which is introduced through the prosthesis. The seal of the anastomosis is obtained by inflating a balloon anchoring the stent with the spikes in the prosthesis and in the receiving artery. This experiment was conducted in three phases: (1) A feasibility study was done on four cadaveric femoral arteries using a polytetrafluoroethylene prosthesis, with measurement of the penetration of the spikes into the layers of the arterial wall. (2) Bench tests were conducted in seven automated and in seven sutured anastomoses. Anastomosis sealing was tested using a pump system (≤250 mm Hg) in a water-filled closed circuit. (3) The infrarenal aorta of seven pigs was replaced with a 6- to 8-mm diameter prosthesis, using this automated device for the proximal anastomosis. The distal anastomosis was handsewn on the aortic bifurcation. After completion angiography, animals were euthanized for macroscopic and histologic studies of the aorta, connector, and prosthesis. Explantations were done immediately (2 pigs), and at 15 (2 pigs), at 30 (2 pigs), and 42 days (1 pig). Study end points were the automated anastomosis time compared with manual suturing, leakage, mechanical strength, and patency of the anastomosis together with the histologic changes of the aortic wall in contact with the spiked stent. RESULTS Tests performed on four cadaveric arteries showed complete penetration of the spikes into the arterial wall layers without metal fracture. Tests of traction showed that the median force needed to rupture the automated anastomosis was 18.3 N (interquartile range [IQR], 17.7-19.9 N), with no significant difference from the handmade anastomosis (19.5 N; IQR, 17.9-20.2 N, P = .33). No leakage was demonstrated in vitro with a pulsatile flow and a pressure up to 250 mm Hg. The median automated anastomosis time on pig aorta was 2.4 minutes (IQR, 1.4-3.3 min) vs 17.0 minutes (IQR, 15.1-17.2 minutes) for the handmade aortic anastomosis performed on the same animals (P = .002). There was no anastomotic leak. Histology showed incorporation of the connector spikes in the aortic wall, without intimal hyperplasia or false aneurysm. CONCLUSIONS This preliminary study confirms the feasibility of this sutureless system, suggesting its usefulness for a faster and simpler anastomosis in hybrid arterial surgery.

French multicenter experience with the GORE TIGRIS Vascular Stent in superficial femoral and popliteal arteries

Background: Preliminary results in small single‐center studies after stenting with the GORE TIGRIS Vascular Stent (W. L. Gore & Associates, Flagstaff, Ariz) show promising short‐term primary patency rates, but larger, multicenter studies are needed. This study therefore investigated the performance of the GORE TIGRIS Vascular Stent at three different centers in France in patients with symptomatic peripheral artery disease. Methods: This retrospective, single‐arm, multicenter cohort study included 215 patients with peripheral artery disease (Rutherford‐Becker category 2‐6) who were treated with the GORE TIGRIS Vascular Stent, a dual‐component stent consisting of a nitinol wire frame combined with a fluoropolymer‐interconnecting structure. The efficacy end point was primary patency defined by freedom from binary restenosis as derived by duplex ultrasound imaging until 2 years after the intervention. Primary, secondary, and primary assisted patency rates at 3, 6, 12, 18, and 24 months were estimated by Kaplan‐Meier analysis. Results: The GORE TIGRIS Vascular Stent was used to successfully treat 239 lesions, of which 141 lesions were located in the superficial femoral artery and 98 in the popliteal artery. Patients were a mean age of 74 ± 12 years. Mean lesion length was 86.8 ± 44.7 mm. After 12 and 24 months, the overall primary patency rates were 81.5% and 67.2%, respectively, and primary assisted patency was 94.9% and 84.8%. Secondary patency was achieved in 99.1% at 24 months. Conclusions: Our multicenter experience with the GORE TIGRIS Vascular Stent demonstrates continued good results at 2 years for endovascular treatment of challenging obstructive superficial femoral artery and popliteal artery disease.

Preliminary Experimental Study of a Mechanical Connector Allowing Vascular Anastomosis

BACKGROUND Aortic clamping time needed to carry out anastomosis during aortic surgery is one of the major predictive factors of morbidity/mortality. Because of the difficulties inherent in this technique, the duration of aortic clamping can be increased significantly with laparoscopy, which may explain why this kind of surgery is not often undertaken. We designed an original connector that will help us perform automated end-to-end vascular anastomoses. This anastomotic device was tested on a cadaver, test benches, and finally on pigs. METHODS The connector consists of a bare-metal stent with spikes covering its outer surface. Once the prosthesis has been introduced into the arterial lumen over a 15-mm length, the connector is placed into the prosthesis; then, upon inflating a balloon and employing stent spikes, the prosthesis can be anchored in the artery. A feasibility study was carried out, first on cadaveric arteries and then on bench tests. In vivo, using this connector, the infrarenal aorta of 7 pigs was replaced with a 6-8-mm-diameter prosthesis. One to 42 days after implantation, angiography was performed before explanting the prosthesis. Evaluation criteria included anastomosis performance time, leakproofing capacity, tensile strength, patency, and histologic changes induced by the device. RESULTS On the cadavers, manual traction tests showed that the anastomoses were satisfactory. Median force needed to rupture an automated anastomosis was 15.85 N. No leakage was seen under a systolic/diastolic pressure of up to 250/180 mm Hg. All pigs benefited from automated anastomosis. Once the designed device had been assessed, the median connection time was 2 minutes. In 4 cases, aortic thrombosis was found, 1 of which was septic. The implanting ancillary was responsible for 2 posterior aortic wall perforations, which extended the clamping time; therefore, this device should be modified. Anastomosis patency and tensile strength tests were satisfactory. Histologic results showed the connector incorporation, integration of the spikes in the arterial wall, and the absence of inflammation in the aortic wall. CONCLUSIONS These preliminary studies confirm that the connector is quick and reliable for performing in vivo arterioprosthetic anastomoses. Further studies are needed to improve the ancillary device, which will enable its use it in laparoscopic and conventional surgery.