Ibrahim Aboshady

A pilot study of a triple antimicrobial-bonded Dacron graft for the prevention of aortic graft infection

OBJECTIVEnPerioperative infection of an aortic graft is one of the most devastating complications of vascular surgery, with a mortality rate of 10% to 30%. The rate of amputation of the lower limbs is generally >25%, depending on the graft material, the location of the graft and infection, and the bacterial virulence. In vitro studies suggest that an antibiotic-impregnated graft may help prevent perioperative graft infection. In a pilot animal study, we tested a locally developed technique of bonding Dacron aortic grafts with three antimicrobial agents to evaluate the ensuing synergistic preventive effect on direct perioperative bacterial contamination.nnnMETHODSnWe surgically implanted a 6-mm vascular knitted Dacron graft in the infrarenal abdominal aorta of six Sinclair miniature pigs. Two pigs received unbonded, uninoculated grafts; two received unbonded, inoculated grafts; and two received inoculated grafts that were bonded with chlorhexidine, rifampin, and minocycline. Before implantation, the two bonded grafts and the two unbonded grafts were immersed for 15 minutes in a 2-mL bacterial solution containing 1 to 2 × 10(7) colony-forming units (CFU)/mL of Staphylococcus aureus (ATCC 29213). Two weeks after graft implantation, the pigs were euthanized, and the grafts were surgically excised for clinical, microbiologic, and histopathologic study.nnnRESULTSnThe two bonded grafts treated with S aureus showed no bacterial growth upon explant, whereas the two unbonded grafts treated with S aureus had high bacterial counts (6.25 × 10(6) and 1.38 × 10(7) CFU/graft). The two control grafts (unbonded and untreated) showed bacterial growth (1.8 × 10(3) and 7.27 × 10(3) CFU/graft) that presumably reflected direct, accidental perioperative bacterial contamination; S cohnii ssp urealyticus and S chromogenes, but not S aureus, were isolated. The histopathologic and clinical data confirmed the microbiologic findings. Only pigs that received unbonded grafts showed histopathologic evidence of a perigraft abscess.nnnCONCLUSIONSnOur results suggest that bonding aortic grafts with this triple antimicrobial combination is a promising method of reducing graft infection resulting from direct postoperative bacterial contamination for at least 2 weeks. Further studies are needed to explore the ability of this novel graft to combat one of the most feared complications in vascular surgery.

Frame isotropic multiresolution analysis for micro CT scans of coronary arteries

We analyze localized textural consistencies in high-resolution Micro CT scans of coronary arteries to identify the appearance of diagnostically relevant changes in tissue. For the efficient and accurate processing of CT volume data, we use fast algorithms associated with three-dimensional so-called isotropic multiresolution wavelets that implement a redundant, frame-based image encoding without directional preference. Our algorithm identifies textural consistencies by correlating coefficients in the wavelet representation.

Prevention of perioperative vascular prosthetic infection with a novel triple antimicrobial-bonded arterial graft

OBJECTIVEnPreviously, we investigated a locally developed technique of bonding arterial grafts with three antimicrobials to protect against early (within 2xa0weeks) perioperative bacterial contamination encountered occasionally during aortic graft prosthetic reconstruction. Vascular graft infections are classified by their appearance time (early [<4xa0months] vs late [>4xa0months] after graft implantation), degree of incorporation into the surrounding vessel wall, connectivity to the postoperative wound, and extent of graft involvement. In the current phase of testing, we evaluated the ability of our novel triple antimicrobial-bonded graft to prevent infection in the first 8xa0weeks after implantation.nnnMETHODSnIn nine Sinclair miniature pigs, we surgically implanted a 6-mm vascular Dacron patch graft in the infrarenal abdominal aorta. Five pigs received grafts chemically bonded with a 60-mg/mL solution of rifampin, minocycline, and chlorhexidine, and four pigs received unbonded grafts. Before implantation, the five bonded grafts and three of the unbonded grafts were immersed for 15xa0minutes in a 2-mL solution containing 1-2xa0× 107xa0colony-forming units (CFUs)/mL of Staphylococcus aureus (ATCC 29213); the fourth unbonded graft served as a control.nnnRESULTSnAt week 9, all of the grafts were explanted. All S aureus-inoculated bonded grafts (nxa0= 5) showed no bacterial growth. The unbonded, uninoculated graft (nxa0= 1) showed low-level bacterial growth (<1.2xa0× 103xa0CFUs); S cohnii spp urealyticus, but not S aureus, was isolated, which suggested accidental direct perioperative contamination. Two pigs that received S aureus-inoculated, unbonded grafts were euthanized because of severe S aureus infection (<6.56xa0× 108xa0CFUs per graft). Results of histopathologic analysis were concordant with the microbiologic findings. Most intergroup differences were observed in the inflammatory infiltrate in the aortic wall at the site of graft implantation. In all pigs that received bonded grafts, Gram staining showed no bacteria.nnnCONCLUSIONSnOur triple-bonded aortic graft prevented perioperative aortic graft infection for at least 8xa0weeks in a porcine model. The synergistic antimicrobial activity of this graft was sufficient to prevent and/or eradicate infection during that period. Further studies are needed to assess the grafts ability to combat early-onset vascular graft infection for up to 4xa0months.

Quantification of roughness of calcific deposits in computed tomography scans of human coronary arteries

Objectives:The incidence of coronary artery disease has been shown to be greater in patients with calcific deposits than in those without. It has been suggested that the pattern of distribution of coronary calcific deposits within coronary arteries is of greater predictive value for acute coronary events than the overall quantity. Whether roughness of calcific deposits is a predictor of acute coronary events is not known. We derived and tested an algorithm, Voxel-Based Bosselation (VBB), for noninvasive quantification of roughness of calcific deposits in human coronary arteries imaged by computed tomography (CT). Methods and Results:VBB was tested on 213 coronary calcific deposits from electron beam CT scans of 27 patients. This algorithm evaluates the 3-dimensional connectedness of surface voxels of each deposit: smooth masses have low VBB and rough masses high VBB. The algorithm was calibrated with artificially generated phantoms as well as background noise mimicking calcific deposits and surrounding heart tissue. The VBB algorithm is applicable to calcific deposits of all scales and gradations. The VBB values of the deposits in this study did not correlate with deposit size further supporting its validity as a measurement of roughness. The VBB index corresponded directly with visual reconstruction using Phong-shaded algorithms. Conclusions:The VBB index, derived here, is a noninvasive method of quantifying the roughness of calcific deposits in CT scan data which can now be used in future clinical studies to determine possible correlations with increased plaque vulnerability and major acute coronary events.

Flat-panel versus 64-channel computed tomography for in vivo quantitative characterization of aortic atherosclerotic plaques☆

BACKGROUNDnFlat-panel computed tomography (FpCT) provides better spatial resolution than 64-channel CT (64-CT) and may improve in vivo quantitative assessment of atherosclerotic plaques.nnnMETHODS AND RESULTSnLesions in 184 aortic histology sections from 6 Watanabe heritable hyperlipidemic rabbits were quantitatively compared with 64-CT (image thickness, 0.625 mm) and FpCT (image thickness, 0.150 mm) images. Images were re-oriented perpendicular to the vessel centerline. For detecting plaque, FpCT and 64-CT were not significantly different (sensitivity, 76% vs 66%; P=NS). Although FpCT was significantly more sensitive (42% vs 0%; P=<0.001) for detecting eccentric lesions, the area under the curve (AUC) for FpCT (0.6) was not significantly different from that for 64-CT (0.45; P=NS). In detecting plaques with ≤ 10% lipid (low attenuation foci), FpCT was significantly more sensitive than 64-CT (24% vs 0.7%; P<0.00) and had a significantly greater AUC (0.6 vs 0.5; P<0.006). Additionally, FpCT was more sensitive (65% vs 0%; P<0.00) in detecting plaques with ≤ 5% calcium (high attenuation foci) but not in detecting branch points. Both FpCT and histology allowed us to detect low-attenuation foci as small as 0.3mm in diameter, whereas 64-CT allowed us to detect only low-attenuation foci ≥ 1.5mm in diameter.nnnCONCLUSIONSnFlat-panel CT seemed to have more potential for quantitatively screening low-risk small atherosclerotic lesions, whereas 64-CT was apparently more useful when imaging established, well-characterized lesions, particularly when measuring the vascular wall thickness in a rabbit model of atherosclerosis.