Fabien Thaveau

Influence of the Textile Structure on the Degradation of Explanted Aortic Endoprostheses

OBJECTIVES To investigate mechanisms of textile failure in explanted human aortic endoprostheses. MATERIALS AND METHODS Endoprostheses (n31) underwent optical and scanning electron microscopy, filament dynamometry, and saturation index measurement. RESULTS The macroscopic lesions observed in the Stentor and Vanguard devices were holes at the extremities of the stents and slipping of the warp yarns at the level of sutures or of the longitudinal seams. The macroscopic lesions observed in AneurX endoprostheses were holes, slipping of the warp yarns and ruptures of the ligatures. The macroscopic lesions observed in the two Talent endoprostheses were sections of fibers at the level of the suture holes and few areas lesions of wear, with sometimes holes at the contact of the stent extremities. Stentor, Vanguard and AneurX all demonstrated low saturation indexes of the fabric (44-59%) with an important anisotropy. Whereas the Talent endograft demonstrated a high index of saturation (124-131%) with a low anisotropy. We did not demonstrate significant polymer degradation in any of the endoprostheses. CONCLUSIONS It is essential to take into account the saturation index to optimally choose a woven textile for the construction of an endoprosthesis since this property of the textile may contribute to explain the macroscopic lesions observed. We did not observe significant polymer degradation by filament dynamometry but further studies are needed to confirm these data.

Current modifications to totally laparoscopic “apron technique”

Since our original description in 1997 of a totally laparoscopic technique for treatment of aortoiliac disease, this type of minimally invasive procedure has been used both in the United States and abroad. We describe improvements that should make this technique more easily reproducible. This modified procedure was offered to six patients, one of whom received a tube graft for treatment of aneurysm disease.

Ischemia reperfusion injury, ischemic conditioning and diabetes mellitus

Ischemia/reperfusion, which is characterized by deficient oxygen supply and subsequent restoration of blood flow, can cause irreversible damages to tissue. Mechanisms contributing to the pathogenesis of ischemia reperfusion injury are complex, multifactorial and highly integrated. Extensive research has focused on increasing organ tolerance to ischemia reperfusion injury, especially through the use of ischemic conditioning strategies. Of morbidities that potentially compromise the protective mechanisms of the heart, diabetes mellitus appears primarily important to study. Diabetes mellitus increases myocardial susceptibility to ischemia reperfusion injury and also modifies myocardial responses to ischemic conditioning strategies by disruption of intracellular signaling responsible for enhancement of resistance to cell death. The purpose of this review is twofold: first, to summarize mechanisms underlying ischemia reperfusion injury and the signal transduction pathways underlying ischemic conditioning cardioprotection; and second, to focus on diabetes mellitus and mechanisms that may be responsible for the lack of effect of ischemic conditioning strategies in diabetes.

Long-Term Outcomes of Direct and Indirect Below-The-Knee Open Revascularization Based on the Angiosome Concept in Diabetic Patients with Critical Limb Ischemia

BACKGROUND We compared long-term outcomes of isolated below-the-knee (BTK) bypass revascularization in diabetic patients presenting with critical limb ischemia (CLI) with and without achieving the bypass on the artery corresponding to the territory of the lesion based on the angiosome concept. MATERIALS We analyzed outcomes of 58 consecutive CLI limbs of 54 diabetic patients presenting with tissue loss who underwent isolated BTK bypasses from 2003 to 2009 for crural occlusive arterial disease. Bypasses were classified into direct and indirect groups based on the angiosome concept, whether feeding artery flow to the site of ischemic tissue loss was achieved or not. We compared median ulcer-healing time, survival, primary patency, and limb salvage rates between both groups by Kaplan-Meier analysis and log-rank test. Independent factors of major amputations were explored by univariate analysis. Variables with P < 0.2 in univariate analysis were submitted to multivariable analysis. RESULTS Median ulcer-healing time was 56 ± 18 days in direct group (n = 36) and 112 ± 45 days in indirect group (n = 22, P = 0.01). There was no difference between both groups in terms of survival or primary patency. Limb salvage rate was significantly higher in direct group than in indirect group: 91% vs. 66% at 1 year, 65% vs. 24% at 3 years, and 58% vs. 18% at 5 years, respectively (P = 0.03). After multivariable Cox proportional analysis, independent factors associated with major amputation were end-stage renal disease (P = 0.030) and C-reactive protein level (P = 0.025). CONCLUSIONS Achieving a direct arterial flow based on angiosome concept in CLI diabetic patients presenting with tissue loss appears to be important for ulcer healing and limb salvage.

Mechanisms of Rupture of Knitted Polyester Vascular Prostheses: An In vitro Analysis of Virgin Prostheses

OBJECTIVES Previous explant retrieval studies have shown ruptures occurring on the remeshing line and the guide line of two types of warp-knitted grafts. The aim of our study was to characterize the mechanisms these ruptures. MATERIALS AND METHODS We performed an in vitro study of the mechanical and chemical characteristics of virgin prostheses. We studied 2 virgin polyester warp-knitted grafts models: the Cooley Double Velour and the Microvel Double Velour constructed by Meadox (USA), using the following techniques: characterization and de-knitting of the textile structure, circumferential tensile strength, filament dynamometry, critical dissolution time of the filaments and scanning electron microscopy. RESULTS Both prostheses were constructed in the same way but the texturized yarns of the Cooley graft included twice as many filaments (54) than the Microvel (27). There was more adsorbed tension in the Cooley structure than in the Microvel. The circumferential tensile strength test demonstrated that the Cooley graft always ruptured on the remeshing line and the Microvel graft always ruptured at the interface between the remeshing line and the standard line. Filament dynamometry demonstrated a heterogeneous behavior of the filaments inside the yarns, mainly at the remeshing line of the Cooley graft (27.1 cN/tex +/- 11.5% versus 26.1 cN/tex +/- 2.2% for the guide line and 28 cN/tex +/- 6.7% for the standard knit). Critical dissolution time of the filaments was significantly lower for the Microvel grafts (2.5 sec versus 17.2 sec for the Cooley). CONCLUSIONS Rupture of knitted polyester prostheses are probably an underestimated phenomenon. They may occur at specific areas of the graft. Further studies are required to determine whether all grafts of this type are at risk.

Contralateral Leg as a Control During Skeletal Muscle Ischemia-Reperfusion

BACKGROUND Recent data demonstrated that hind limb ischemia induces skeletal muscle mitochondrial dysfunctions. Improvement of such metabolic myopathy improves patients symptomatology, supporting the development of experimental models focused on mitochondrial function analysis. However, although the nonischemic contralateral leg is often used as a control during unilateral leg ischemia, whether it might be useful when assessing ischemia-induced mitochondrial dysfunction remains to be investigated. MATERIALS AND METHODS Both ischemic (IR) and nonischemic contralateral legs (CTL) of rats (n=13) submitted to 5 h ischemia induced by a rubber band tourniquet applied on the root of the hind limb were studied and compared to that of sham-operated animals (SHAM, n=13). Maximal oxidative capacities (V(max)) and complexes I, II and IV activities of the gastrocnemius mitochondrial respiratory chain were determined, using glutamate-malate, succinate (Vs) and TMPD-ascorbate (V(TMPD)) substrates. RESULTS V(max) was decreased in IR (4.6+/-0.4 microM/min/g dry weight) compared to both SHAM and CTL muscles (8.5+/-0.5 and 7.1+/-0.4 microM/min/g dry weight, -46% and -36%, P<0.001, respectively). V(S) and V(TMPD) were reduced in IR muscle (-56% and -48% for V(S); and -25% and -24% for V(TMPD), P<0.001) as compared to SHAM and CTL). V(S) and V(TMPD) were similar in SHAM and CTL muscles. CONCLUSIONS Five hours ischemia-reperfusion significantly impaired complexes I, II and IV of the ischemic skeletal muscle mitochondrial respiratory chain. Interestingly, only V(max) was slightly altered in the contralateral leg, supporting that the nonischemic leg might be used as a control when assessing mitochondrial function in the experimental setting of unilateral hind limb ischemia.

Methylene Blue Protects Liver Oxidative Capacity after Gut Ischaemia–Reperfusion in the Rat

OBJECTIVES Mesenteric ischaemia/reperfusion (IR) may lead to liver mitochondrial dysfunction and multiple organ failure. We determined whether gut IR induces early impairment of liver mitochondrial oxidative activity and whether methylene blue (MB) might afford protection. DESIGN Controlled animal study. MATERIALS AND METHODS Rats were randomised into three groups: controls (n = 18), gut IR group (mesenteric ischaemia (60 min)/reperfusion (60 min)) (n = 18) and gut IR + MB group (15 mg kg(-1) MB intra-peritoneally) (n = 16). Study parameters were: serum liver function markers, blood lactate, standard histology and DNA fragmentation (apoptosis) on intestinal and liver tissue, maximal oxidative capacity of liver mitochondria (state 3) and activity of complexes II, III and IV of the respiratory chain measured using a Clark oxygen electrode. RESULTS Gut IR increased lactate deshydrogenase (+982%), aspartate and alanine aminotransferases (+43% and +74%, respectively) and lactate levels (+271%). It induced segmental loss of intestinal villi and cryptic apoptosis. It reduced liver state 3 respiration by 30% from 50.1 ± 3 to 35.2 ± 3.5 μM O(2) min(-1) g(-1) (P < 0.01) and the activity of complexes II, III and IV of the mitochondrial respiratory chain. Early impairment of liver mitochondrial respiration was related to blood lactate levels (r(2) = 0.45). MB restored liver mitochondrial function. CONCLUSIONS MB protected against gut IR-induced liver mitochondria dysfunction.

Minilaparotomy for aortoiliac aneurysmal disease: experience and review of the literature.

Abstract: Vascular surgery is evolving, as other specialities, toward minimally invasive techniques. Presently, 3 approaches to aortoiliac disease are suggested as minimally invasive. Besides the endovascular procedures, laparoscopic techniques and minilaparotomy are being advocated. Although for aneurysmal disease, we favor a totally laparoscopic approach, criticisms raised over laparoscopy-assisted techniques by those advocating minilaparotomy led us to investigate the benefits of the latter technique. We first evaluated the procedure in 7 patients with infrarenal abdominal aortic aneurysm (AAA). We found the procedure impossible to perform with an 8- to 10-cm incision in 6 of the 7 patients. This led us to evaluate causes of failure of the technique. It appeared to us that most of our complications were related to inadequate exposure. Fifty consecutive computed tomography scans from patients with AAA of surgical size were then reviewed to evaluate the aneurysm lengths and compare them to the reported lengths of skin incision for minilaparotomy. Results were expressed adding a total of 2 cm for proximal and distal clamping. Only 2% of patients would present with aneurysms suitable for treatment through an 8-cm midline incision and 30% through a 10-cm incision. We then reviewed the literature on minilaparotomy. We believe that minilaparotomy should be reserved for those patients with purely aortic disease and the appropriate body habitus.

Effect of chronic pre-treatment with angiotensin converting enzyme inhibition on skeletal muscle mitochondrial recovery after ischemia/reperfusion

Impaired skeletal muscle energetic participates in peripheral arterial disease (PAD) patient’s morbidity and mortality. Angiotensin converting enzyme inhibition (ACEi), cornerstone for pharmacologic risk factor management in PAD patients, might also be interesting by protecting skeletal muscle energetic. We therefore determined whether chronic ACEi might reduce ischemia‐induced mitochondrial respiratory chain dysfunction in the frequent setting of hindlimb ischemia–reperfusion. Ischemic legs of rats submitted to 5 h ischemia induced by a rubber band tourniquet applied on the root of the hindlimb followed by reperfusion without (IR, n = 11) or after ACEi (n = 14; captopril 40 mg/kg per day during 28 days before surgery) were studied and compared to that of sham‐operated animals (n = 11). The effect of ACEi on the non‐ischemic contralateral leg was also determined in the ACEi group. Maximal oxidative capacities (Vmax) and complexes I, II and IV activities of the mitochondrial respiratory chain of the gastrocnemius muscle were determined using glutamate–malate, succinate and TMPD–ascorbate substrates. Arterial blood pressure was significantly decreased after ACEi (124 ± 2.8 vs. 108 ± 4.19 mmHg; P = 0.01). Ischemia–reperfusion reduced Vmax (4.4 ± 0.4 vs. 8.7 ± 0.5 μmol O2/min/g dry weight, −49%, P < 0.001), affecting mitochondrial complexes I, II and IV activities. ACEi failed to modulate ischemia‐induced dysfunction (Vmax 5.1 ± 0.7 μmol O2/min/g dry weight) or the non‐ischemic contralateral muscle respiratory rate. Ischemia–reperfusion significantly impaired the mitochondrial respiratory chain I, II and IV complexes of skeletal muscle. Pharmacologic pre‐treatment with ACEi did not prevent or increase such alterations. Further studies might be useful to improve the pharmacologic conditioning of PAD patients needing arterial revascularization.

Totally laparoscopic juxtarenal aortic anastomosis: an experimental study.

The surgical management of juxtarenal aneurysms necessitates suprarenal aortic clamping and control of the renal arteries. We attempted to reproduce this procedure laparoscopically. Five female piglets were submitted to a totally laparoscopic approach of the aortoiliac segment. After laparoscopic control of the renal arteries and suprarenal clamping, a 6-mm Dacron tube graft was anastomosed to the juxtarenal aorta. After the procedure, a midline laparotomy allowed verification of the patency of the renal arteries and the quality of the anastomosis. Mean operative time was 198 minutes (range, 170–240 minutes). The dissection took an average of 92 minutes (range, 75–110 minutes). The mean suprarenal aortic cross-clamp time was 46.3 minutes (range, 29.1–81.5 minutes), and the mean anastomotic time was 28.9 minutes (range, 16.5–68.1 minutes). This study demonstrates in this animal model the feasibility of juxtarenal aortic anastomosis using a laparoscopic technique. Newly designed instruments should allow a shorter clamping time in the future.