Zbigniew Zdanowski

Magnetic resonance imaging and MR angiography of endoluminally treated abdominal aortic aneurysms.

OBJECTIVES To evaluate magnetic resonance imaging (MRI) with gadolinium-based contrast medium-enhanced MR angiography (MRA) for the follow-up of endoluminally treated abdominal aortic aneurysms. DESIGN MRI/MRA, angiography and computed tomography (CT) were performed 1 month after endoluminal stent-graft placement. MRI/MRA was repeated at 6 and 12 months and angiography and CT were added to confirm unexpected findings. MATERIALS Fifteen male patients with endoluminally treated abdominal aortic aneurysms. METHODS MRI with MRA, spiral CT with transverse images and angiography were performed. RESULTS MRI/MRA demonstrated changes of stent-graft morphology, aortic neck- and aneurysmal diameter, stent-graft blood flow, stent-graft leakage, blood flow in lumbar arteries, intra-aneurysmal thrombus, periaortic inflammation and vertebral body infarction. For most of these features MRI/MRA provided more information than angiography and/or CT. MRI was the only method demonstrating thrombus reorganisation and vertebral body infarction. CONCLUSIONS MRI with MRA provides the relevant information needed for follow-up of endoluminally treated abdominal aortic aneurysms (AAA). This may be the method of choice because of its use of contrast media with very low nephrotoxicity, lack of ionising radiation and non-invasiveness.

Influence of some plasma proteins on in vitro bacterial adherence to PTFE and Dacron vascular prostheses

The in vitro adherence of Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli (one strain of each species) to commercially available, microporous polytetrafluoroethylene (PTFE) and woven Dacron vascular grafts before and after coating with human plasma was compared. Standard size segments of the materials were incubated with 35S‐labeled bacteria for 0.5–18 h and, following washes, the radioactivity associated with the segment was measured. The binding of each of the tested species to native Dacron was higher than to PTFE. After coating with human plasma, however, the binding of all three species to PTFE was significantly enhanced, whereas the binding to Dacron was reduced. In addition, the influence of coating with serum albumin (HSA), immunoglobulin G (IgG), fibrinogen (Fg) or fibronection (Fn) rather than whole plasma was tested. We found that coating with HSA reduced the binding of all three species to Dacron and of staphylococci to PTFE. IgG decreased the binding of S. epidermidis and E. coli to Dacron and of S. epidermidis to PTFE. In contrast, Fg enhanced the binding of S. aureus both to Dacron and PTFE, and that of E. coli to PTFE, but decreased the binding of S. epidermidis and E. coli to Dacron. Fn enhanced the binding of S. aureus to Dacron, and of E. coli to PTFE, but decreased the binding of S. aureus to PTFE and of S. epidermidis both to PTFE and Dacron. Thus, both whole plasma and some isolated plasma proteins were found to modulate bacterial adherence to two tested graft materials. From a clinical point of view, bacterial binding to plasma‐coated rather than native materials may more adequately determine the likelihood of in vivo colonization of the various materials. Furthermore, precoating of materials with selected proteins may be of value in the prevention of graft colonization.

Influence of heparin coating on in vitro bacterial adherence to poly(vinyl chloride) segments

End-point attached, covalently bound heparin has been shown to be effective in preventing activation of the coagulation cascade by biomaterials. Data concerning its possible influence on bacterial attachment and resistance to biomaterial-associated infection are, so far, lacking. In the present work, the in vitro adherence of Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli, one isolate of each species, to plain poly(vinyl chloride) (plain PVC) and heparin coated poly(vinyl chloride) (EPA-PVC) segments was compared. Also, the influence of precoating the segments with human normal plasma for 2 h was studied. 35S-Methionine was used to radiolabel bacteria. The segments were exposed to bacterial suspensions of approximately 10(7) colony forming units (CFU) per milliliter at 37 degrees C for 0.5-6 h. Following repeated washing in phosphate buffered saline (PBS), radioactivity associated with the segments was measured. Plain PVC as compared to EPA-PVC bound significantly more cells of all three tested species. Plasma precoating significantly decreased adherence of the tested species to plain PVC but did not affect the binding to EPA-PVC. However, after precoating with human plasma, EPA-PVC compared to plain PVC showed a higher binding of S. aureus which might possibly be due to bridging effects of fibronectin or other plasma proteins, interacting with S. aureus.

Outcome of treatment of ruptured abdominal aortic aneurysms depending on the type of hospital

OBJECTIVE To compare the outcome of patients operated on acutely for ruptured abdominal aortic aneurysms (AAA) or otherwise symptomatic aortic aneurysms in a university hospital and in two county hospitals by the same group of vascular surgeons. DESIGN Retrospective study. SETTING 1 university and 2 county hospitals, Sweden. SUBJECTS 108 patients operated on urgently for AAA, 81 at the university hospital, and 27 at the county hospitals between January 1992 and December 1998. INTERVENTION Repair of the AAA. MAIN OUTCOME MEASURES Morbidity and mortality. RESULTS 21 of the 81 patients having urgent repair of an AAA at the university hospital (26%) had been transferred from the county hospitals. Thirteen patients were not operated on, 7 because of their poor general condition and great age (median 84 years), 3 who refused operation, and 3 in whom the diagnosis was incorrect. During the same time period a further 27 haemodynamically unstable patients were operated on by the same vascular surgeons at the county hospitals. The on-table mortality for patients with ruptured AAA and shock was 5/43 (12%) at the university hospital and 4/27 (15%) at the county hospitals. The corresponding in-hospital rates were 11/43 (26%) and 11/27 (41%). Mortality was significantly higher if the operation was delayed by more than 45 minutes. The incidence of postoperative complications was the same in both hospitals. CONCLUSION If a patient with a ruptured AAA and shock is admitted to the county hospital and operated on by a specialist vascular surgeon the outcome is fully acceptable. The difference seems to be related to the postoperative period. To what extent the delay caused by the surgeons journey to the county hospital has any influence on the outcome is not possible to evaluate.

Bacterial Adherence to Synthetic Vascular Prostheses and Influence of Human Plasma. An In Vitro Study

The in vitro adherence of Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli to five commercially available prosthetic vascular graft materials was compared. The influence of precoating the segments with human plasma for 2 h was also studied. S35-methionine was used to radiolabel bacteria. The segments were exposed to bacterial suspensions of approximately 10(7) CFU/ml at 37 degrees C for 0.5-18h. Following repeated washing in phosphate buffered saline (PBS), radioactivity associated with the segments was measured. The adherence of the three clinically relevant bacterial species was higher to untreated Dacron than to gelatin or collagen impregnated/coated Dacron or to PTFE. Furthermore, precoating of grafts with human plasma reduced bacterial adherence to woven Dacron, had a little effect on gelatin coated Dacron, but increased the adherence to collagen treated Dacron and, in particular, to PTFE.

Microvascular Graft Infection in the Rat

Three modes of exposure of PTFE grafts to Staphylococcus aureus strain 763 were compared. It was found that contamination with bacterial suspension containing 108 CFU/ml either before graft implantation or in situ following implantation invariably resulted in graft infection, as revealed by bacterial colonization. Furthermore, the efficiency of these procedures was evident from lack of patency of the infected grafts. When reducing the bacterial concentration to 105 or 103 CFU/ml lower rates of graft infection were noted. Intravenous administration seemed somewhat less effective for establishing graft infection. Finally, our experiment showed a lower resistance to bacterial challenge of microvascular PTFE grafts at implantation than at one week later.