Strain estimation in abdominal aortic aneurysms from 2-D ultrasound.

The rupture risk of abdominal aortic aneurysms (AAAs) is routinely inferred from the maximum diameter of the AAA. However, clinical experience indicates that this criterion has poor accuracy and that noninvasive assessment of the elastic properties of the vessel might give better correspondence with the rupture risk. We have developed a method for analysis of circumferential strain in AAAs from sequences of cross-sectional ultrasound B-mode images. The algorithm is fast, semiautomatic and well-suited for real-time applications. The method was developed and evaluated using data from 10 AAA patients. The preliminary results demonstrate that the method is sufficiently accurate and robust for clinically acquired data. An important finding is that local strain values may exceed the circumferential average strain significantly. Furthermore, the calculated strain shows no apparent covariation with the diagnosed diameter. This implies that the method may give new and essential information on the clinical condition of the AAA.

[Surgical treatment of carotid stenosis in Norway]. / Kirurgisk behandling ved carotisstenose i Norge.

BACKGROUND: Our purpose was to explore indications, preoperative investigation and operative technique for carotid endarterectomy in Norway. MATERIAL AND METHODS: A questionnaire was sent to 22 departments performing vascular surgery. Questions included an evaluation of the volume of carotid surgery, indications, preoperative examination, surgical technique and postoperative follow up. We requested the number of carotid endarterectomies performed in 2002, and whether the hospital also performed endovascular treatment for carotid artery stenosis. RESULTS: Carotid endarterectomy was performed in 19 hospitals, with an average of 16 operations per department. Among the surgeons, 18 stated that the number of carotid endarterectomies in Norway was too low. Endovascular treatment was performed in three hospitals. There was agreement on the indications for carotid endarterectomy for symptomatic stenosis, while the practice for asymptomatic stenosis varied widely. Patients who had undergone a minor stroke, were offered surgery after more than 4 weeks in 10 cases. In 11 departments a neurologist always examined the patient preoperatively. Duplex ultrasound examination of the carotid arteries was usually done by a neurologist; only 6 departments did preoperative conventional angiography in all cases. More than half of the surgeons always used a shunt during the operation, while only a few used intraoperative monitoring. Nine out of 20 surgeons closed the arteriotomy with a patch. INTERPRETATION: Consensus regarding the indications for carotid endarterectomy should be sought and more patients probably be offered surgery soon after the occurrence of symptoms.

Parameters describing motion in carotid artery plaques from ultrasound examination: A reproducibility study.

We have previously developed a method for quantifying motion in carotid artery plaques from sequences of ultrasound (US) radiofrequency images. Here, we examine the intraoperator reproducibility of the results. Five independent recordings were made on each of six symptomatic and six asymptomatic patients, and processed off-line into 29 motion parameters, representing motion amplitude, stretch/compression and shear motion. For the statistical analysis, we used a linear mixed model and investigated the parameters for contributions from individual patients, contributions from recordings on each patient and contributions from heart cycles within each recording. The model was valid for seven parameters calculated over the entire heart cycle (four calculated over the systole only), which all showed good reproducibility (intraclass coefficient for variance over all patients rho(alpha) >/= 0.4). Averaging three recordings of two heart cycles each gives acceptable accuracy (normalised variance of patient means lambda < 0.3). This acquisition scheme is reasonable in a clinical situation.

A new method for analysis of motion of carotid plaques from RF ultrasound images.

Motion of carotid artery plaques during the cardiac cycle may contribute to plaque disruption and embolism. We have developed a computerized method that objectively analyzes such motion from a sequence of ultrasound (US) radiofrequency (RF) images. A displacement vector map is obtained by 2-D correlation of local areas in consecutive images. From this map, motion dynamics can be quantified and presented as function of time, spatial (image) coordinates or as single numbers. Correct functionality has been verified on laboratory data. Applied to patient data, the method gives temporal results that correlate well with ECG data and the calculated peak systolic velocities of typically 10 mm/s agree well with values reported in the literature. The spatial analysis demonstrates that different plaque regions may exhibit different motion patterns that may cause internal stress, leading to fissures and plaque disruption. Thus, the motion analysis method may provide new and important information about the plaque characteristics and the prospective risk of cerebrovascular events.

[Nine years' experience with endovascular treatment of abdominal aortic aneurysms]. / Ni års erfaring med endovaskulaer behandling av abdominale aortaaneurismer.

BACKGROUND: Endovascular repair of abdominal aortic aneurysm was started nine years ago at our institution. Our purpose was to evaluate the results over this period. MATERIAL AND METHODS: From 1995 to 2003, a total of 148 patients were treated for infrarenal abdominal aortic aneurysms by endovascular repair. The material includes 31 patients (21%) who were unfit for open surgery because of comorbidity or poor general condition. The patients have been followed up at regular intervals with clinical investigation, plain abdominal X-ray, and CT scans. Regional anaesthesia was used for 143 procedures; 5 were carried out under general anaesthesia. RESULTS: 30-day mortality following elective procedures was 2.3%. 31 endo-leaks were observed, 16 early and 15 late. Furthermore, 22 graft limb occlusions were diagnosed and thirteen of them repaired with femoro-femoral bypass. Secondary procedures were necessary in 42 (28.4%) of the patients, including 7 late conversions to open surgery. Some patients had more than one secondary procedure. With better stent grafts, the incidence of complications and secondary procedures has decreased significantly. During the last 4.5 years, only 4 secondary procedures (5.8%) have been necessary in 69 patients. In the total material the accumulated five-year survival rate was about 60%. INTERPRETATION: Results from endovascular repair of abdominal aortic aneurysm have improved in recent years. Ongoing prospective randomised studies could give us the information we need in order to establish what role this treatment should have.

Aortic graft infection and mycotic aneurysm with Streptococcus equi zooepidemicus: two cases with favorable outcome of antibiotic treatment.

Infections with Streptococcus equi zooepidemicus are rare and are associated with contact with animals or animal products. There are very few reports about infected vascular grafts or aneurysms with this etiology. We present two patients. The first is a 77-year-old man with an infected bifurcated graft four years after an open operation for an abdominal aortic aneurysm (AAA). The second is a 72-year-old man with a symptomatic mycotic AAA, treated with endovascular aneurysm repair. Both received prolonged treatment with bactericidal antibiotics and responded well. Follow-up time at present is 5.5 years for the first, and 4.5 years for the second, patient.

Reduced strain in abdominal aortic aneurysms after endovascular repair.

PURPOSE: To compare in vivo strain in abdominal aortic aneurysms before and after endovascular aneurysm repair (EVAR), thereby obtaining a quantitative measure of changes in mechanical burden on the aneurysm wall. METHOD: Transabdominal ultrasound was acquired from 10 patients (9 men; median age 76 years, range 61-83) 1 day before and 2 days after elective EVAR. Strain was estimated as the relative cyclic elongation and contraction of the wall tissue in a number of connected segments along the aneurysm circumference. For each time instance of the cardiac cycle, the maximum and the average strain values along the circumference were recorded. The temporal maximums of these parameters (defined as the maximum strain and the peak average strain, respectively) were compared before and after EVAR. RESULTS: Both maximum strain and peak average strain were reduced following EVAR by 41% (range 35%-63%) and 68% (range 41%-93%), respectively. Despite the reduction, cyclic strain was still evident after the stent-graft was placed, even when no evidence of endoleak was found. Further, the strain values were inhomogeneous along the circumference, both before and after treatment. In 2 cases, endoleak was proven by routine computed tomography; the relative reduction in maximum strain was slightly less in these cases (35% and 38%) compared to those without endoleak (45%, range 38%-63%). No difference was found in reduction of peak average strain. CONCLUSION: Strain is significantly reduced after EVAR, but there may still be a certain level of strain after the treatment. The strain values are inhomogeneous along the circumference both before and after treatment. These results encourage further investigation to evaluate the potential for using circumferential strain as an additional indicator of outcome after endovascular repair.

Initial observations of endovascular aneurysm repair using Dyna-CT.

PURPOSE: To examine the feasibility of a new technology that provides images resembling computed tomographic (CT) slices on the operating table during elective endovascular abdominal aortic aneurysm (AAA) repair (EVAR). TECHNIQUE: Commercially available Dyna-CT equipment was used in conjunction with Voxar 3D software for image reconstruction. During the preliminary evaluation of 9 patients (7 men; median age 73 years, range 67-84) with non-ruptured AAA undergoing elective EVAR with the Zenith Trifab stent-graft under regional anesthesia, the equipment functioned sufficiently well to produce the planned image dataset in 8 of 9 patients. Rotation failed in 1 overweight individual due to a short distance between the patient's abdomen and the C-arm. In 7 of 8 patients, the radiologist was able to measure the diameter of the aneurysm, and it was possible to visualize the entire length of the treated aorta and the iliac arteries in all cases. The proximal aortic neck, including the stent-graft, was visualized in 7 cases. No endoleak or other complications was detected, which was confirmed on the pre-discharge CT scans. The time interval from the rotation of the C-arm until the appearance on the monitor of the first automatically generated 3D images was 7 minutes, which has subsequently been reduced to approximately 2 minutes. CONCLUSION: Our preliminary experience with Dyna-CT is promising, but further research is necessary to define the place of this imaging modality in EVAR.

Endovascular repair of abdominal aortic aneurysm in octogenarians: an analysis based on EUROSTAR data.

PURPOSE: To investigate the early and late outcome after endovascular treatment of abdominal aortic aneurysm (EVAR) in octogenarians compared with patients aged < 80 years. METHODS: Patients treated for abdominal aortic aneurysm (AAA) with endovascular repair during the period 1996 to 2004 were collated in the EUROSTAR registry. This study group consisted of 697 patients aged > or = 80 years. Comparison was made with 4198 patients aged < 80 years with regard to the incidence of preoperative characteristics and outcomes of the procedure. RESULTS: The proportion of octogenarians treated by EVAR increased during the study period, from 11% in the first year to 18% in the last year. Octogenarians more frequently had cardiac disease, impaired renal function, and pulmonary disease (P = .03, P < .0001 and P = .0001). Thirty-two percent of the octogenarians were recorded unfit for open surgery as opposed to 22% in younger patients (P < .0001); they also had a larger aneurysm diameter (62 vs 58 mm, respectively; P < .0001). The 30-day and in-hospital mortality in octogenarians was 5% vs 2% in the younger group (P < .0001). More device-related complications and systemic complications, including cardiac disease, were noted in octogenarians (7% vs 5% and 19% vs 11%, P = .03 and P < .0001, respectively). This group of patients also had a higher incidence of postoperative hemorrhagic complications, including hematoma (7% vs 3%, P < .0001, respectively). No differences in conversion to open repair and post-EVAR rupture rate were observed. Aneurysm-related mortality and late all-cause mortality was 7% vs 3% and 10% vs 7%, both P < .0001. CONCLUSION: Our study supports that EVAR might be considered when treating elderly patients, provided their aneurysms are anatomically suited for the endovascular technique. The risk for late complications compared with open repair may be outweighed by a lower early mortality as well as a shorter time for physical recovery.

Iohexol-induced neutrophil myeloperoxidase release and activation upon contact with vascular stent-graft material: a mechanism contributing to the postimplantation syndrome?

PURPOSE: To investigate whether the contrast medium iohexol alone or in combination with vascular stent-graft material induces neutrophil degranulation. METHODS: Human whole blood or isolated human neutrophils were incubated with or without iohexol and vascular stent-graft material. Samples were also drawn from 5 patients undergoing diagnostic angiography using iohexol. Myeloperoxidase and lactoferrin concentrations were determined by enzyme immunoassays. RESULTS: Both in vitro and in the patients, iohexol induced neutrophil degranulation with considerable individual variation in dose sensitivity and timing. The in vitro effect was independent of the type of anticoagulant used (ethylenediamine tetra-acetic acid, heparin, lepirudin). Experiments using isolated neutrophils showed that degranulation was independent of complement activation or platelet-derived mediators. The dose for maximal response varied from 5 to 50 mg I/mL (10.7-107.6 mg/mL iohexol). In vitro, vascular stent-graft material alone did not induce neutrophil degranulation. As compared to iohexol alone, incubation with iohexol and vascular stent-graft material in combination substantially increased the release of myeloperoxidase. CONCLUSIONS: Iohexol induces neutrophil degranulation, which is greatly enhanced when combined with vascular stent-graft material. Thus, iohexol-induced neutrophil activation may contribute to an inflammatory response following stent-graft implantation. We speculate that neutrophil activation during other procedures combining catheters and iohexol (e.g., angiography) may induce inflammation, which might have detrimental effects.