Mohamed Baguneid

Shear‐stress preconditioning and tissue‐engineering‐based paradigms for generating arterial substitutes

In situ tissue engineering using shear‐stress preconditioning and adhesive biomolecules is a new approach to autologous tissue engineering. In the present study, novel tissue‐engineering grafts (TEGs) were preconditioned within an in vitro pulsatile flow circuit, with and without the addition of fibronectin (FN), to establish whether low‐shear‐stress conditions promoted endothelial cell (EC) retention and differentiation. TEGs (n=24) were generated by the contraction and compaction of collagen(I) by porcine aortic smooth‐muscle cells (SMCs) on to a compliant polyester graft scaffold. ECs were radiolabelled with [111In]indium tropolonate and seeded on to the luminal surface of the TEGs. Following organ culture in a bioreactor (7 days), TEGs were split into four groups (n=six TEGs per group): Group A acted as controls with TEGs unmodified and seeded with radiolabelled ECs; Group B underwent luminal pre‐coating with FN (75 μg/ml) prior to EC seeding; Group C underwent preconditioning within a pulsatile flow circuit at 10–20 μN (1–2 dyn)/cm2 for 7 days prior to EC seeding, and Group D TEGs were preconditioned for 7 days at 1–2 dyn/cm2, followed by luminal pre‐coating with FN prior to EC seeding. The resistance to physiological shear stress of the seeded ECs was assessed using a γ‐radiation counter within a physiological flow circuit producing an arterial waveform with a mean shear stress of 93.2 μN (9.32 dyn)/cm2. Environmental scanning electron microscopy (ESEM) was used to determine the distribution and degree of differentiation of the attached Ecs, and tissue‐type‐plasminogen‐activator (tPA) assays provided a measure of function and viability. EC resistance to shear stress at 93.2 μN/cm2 was significantly enhanced by a period of preconditioning (Group C) at 10–20 μN/cm2, surface modification with FN (Group B), or both (Group D) when compared with control grafts (Group A). However, TEGs coated with FN whether preconditioned (Group D) or not (Group B) demonstrated the best results for EC retention. ESEM demonstrated near‐confluent differentiated flattened ECs in both these cases. EC function was demonstrated by a steady increase in tPA production. Low‐shear‐stress preconditioning of TEGs enhances EC retention in vitro with an additional advantage demonstrated by pre‐treatment with FN prior to endothelialization. These findings may be exploited in the development of tissue‐engineered constructs to maintain a confluent endothelial lining.

Outcome of transaxillary rib resection for thoracic outlet syndrome — a 10 year experience ☆

BACKGROUNDnThis study assessed the outcome of transaxillary first and/or cervical rib resection in a unit, which has a policy of combined assessment by a neurologist and vascular surgeon.nnnMETHODSn61 patients underwent 83 transaxillary rib resections for thoracic outlet syndrome. A retrospective case note review of these patients was undertaken. All patients completed a telephone questionnaire regarding long-term outcome.nnnRESULTSnPost-operative outpatient assessment at a median of 6 months recorded 91.5% improved, of whom 61.5% were symptom-free. 61% were available for the telephone questionnaire at a median follow-up of 4 yr. 74% reported an improvement, with complete resolution in 58%. Six described temporary improvement following surgery.nnnCONCLUSIONnTransaxillary rib resection is a safe and effective procedure, allowing almost two thirds of patients a return to normal activity. Combined assessment by vascular and neurological teams may help in patient selection for surgery, as well as the accurate long-term assessment of outcome.

Management of Acute Nontraumatic Upper Limb Ischemia

A retrospective review of all patients presenting to a tertiary referral center with acute nontraumatic upper limb ischemia between January 1992 and June 1997 was under taken to examine the role of intraarterial thrombolysis in the management of such cases. Twenty-one patients were identified in the radiology and vascular surgery departments registers. Twenty (95%) underwent angiography, demonstrating subclavian artery occlusion in four, axillary in two, brachial in 13, and one at the digital level. Intraarterial thrombolysis was attempted in 12 patients. There were three technical failures, all requiring embolectomy. Six had complete lysis and resolution of their symptoms. One patient had partial lysis but experienced no further rest pain. Thrombolysis was unsuc cessful in two cases with one subsequently requiring embolectomy and the other surgical bypass. Three patients had surgical intervention as their primary procedure with two favorable outcomes and one ending in above-elbow amputation. Five patients were treated conservatively with heparin, resulting in three partial and two full recoveries. One patient experienced complete resolution of symptoms with an intravenous prosta cyclin infusion. Both electrocardiograms (ECG) and echocardiograms (ECHO) were of limited diagnostic aid, and long-term warfarin anticoagulation was prescribed to all patients. There was no recurrence of upper limb ischemia at a median follow up of 18 months. Intraarterial thrombolysis is an effective first line treatment for acute nontrau matic upper limb ischemia in selected cases.

Erectile dysfunction after open versus angioplasty aortoiliac procedures: a questionnaire survey.

Erectile dysfunction (ED) is a common complication after aortoiliac surgery. The aims of this study were to determine the incidence of ED in patients with aortoiliac occlusive disease or aneurysm and evaluate the effect of revascularization by means of open surgery or iliac angioplasty/stenting upon erectile function by using the new International Index of Erectile Function (IIEF) questionnaire. All male patients who had previously undergone open aortoiliac reconstruction or iliac angioplasty/stenting and who were alive at the time of this study were first contacted by telephone. Those who agreed to take part in the study were sent anonymous IIEF questionnaires. Patients were asked to recall their sexual function before and 3 months after the procedure. ED was defined as IIEF score of <11. After telephone interview, a total of 116 patients agreed to take part in the study. The response rate was 61%. Two patients, one in each group, had ED preoperatively. The preoperative IIEF scores were no different in surgery and angioplasty/stenting groups (p=0.3). Overall, 46/63 patients reported worsening erectile function postoperatively. In the surgery group (n=37), 32 patients reported deterioration of their sexual function, 3 no change, and 2 improvement, while in the angioplasty/stenting group (n=26), 14 patients had deterioration, 11 no change, and 1 improvement. In both groups, the IIEF score decreased significantly postintervention; however, the deterioration was much more pronounced after open surgery (p<0.001). Of the 61 patients with “normal” erectile function (IIEF= 11), 10 patients (28%) developed ED following surgery, but none after angioplasty/ stenting (p=0.003). As judged by the IIEF, a significant proportion of patients undergoing open and endovascular procedures experience worsening sexual function.

Prediction of Cardiac Risk prior to Elective Abdominal Aortic Surgery: Role of Multiple Gated Acquisition Scan

Debate continues regarding the value of cardiac testing before major vascular surgery. Studies looking at whether a low radioisotope left ventricular ejection fraction (LVEF) could reliably predict postoperative cardiac events have produced conflicting results. Technetium-99m multiple gated acquisition (MUGA) scanning was employed in 122 patients undergoing elective abdominal aortic aneurysm surgery to estimate the resting LVEF and to detect regional or global myocardial wall motion abnormalities (WMAs). Adverse cardiac outcomes were predicted using logistic regression analysis. Among this group of patients, 20 did not proceed to surgery for a variety of reasons, and 102 underwent surgical repair. More than half of the patients (55%) had a history of cardiac disease. The mean ± SD LVEF was 55.5% ± 11.1%. Altogether, 31 patients had WMAs, and 21 had both WMAs and an abnormal LVEF (≤ 50%). Altogether, 20 cardiac complications were encountered in 17 patients (17%). Logistic regression analysis identified four significant predictors of cardiac complications: history of cardiac disease [odds ratio (OR) 10.43; 95% confidence interval (CI) 1.3 and 80.5], the presence of WMAs (OR 10.1, CI 1.4 and 74.6), additional procedures (OR 12.1, CI 1.4 and 103.0), and reoperation during the postoperative period (OR 6.4, CI 1.4 and 30.4). This is the largest reported British series of cardiac testing using MUGA scans prior to abdominal aortic reconstruction. Only the presence of WMAs (not the resting LVEF) was useful for predicting postoperative cardiac events. A history of cardiac disease, additional procedures, and reoperation during the postoperative period also place a patient at high risk for cardiac complications. A normal LVEF is by no means reassuring that a patient is at low risk of suffering an adverse cardiac outcome.