In-vivo imaging of changes in abdominal aortic aneurysm thrombus volume during the cardiac cycle.

PURPOSE: To evaluate in-vivo thrombus compressibility in abdominal aortic aneurysms (AAAs) to hopefully shed light on the biomechanical importance of intraluminal thrombus. METHODS: Dynamic electrocardiographically-gated computed tomographic angiography was performed in 17 AAA patients (15 men; mean age 73 years, range 69-76): 11 scheduled for surgical repair and 6 under routine surveillance. The volumes of intraluminal thrombus, the lumen, and the total aneurysm were quantified for each phase of the cardiac cycle. Thrombus compressibility was defined as the percent change in thrombus volume between diastole and peak systole. Continuous data are presented as medians and interquartile ranges (IQR). RESULTS: A substantial interpatient variability was observed in thrombus compressibility, ranging from 0.4% to 43.6% (0.2 to 13.5 mL, respectively). Both thrombus and lumen volumes varied substantially during the cardiac cycle. As lumen volume increased (5.2%, IQR 2.8%-8.8%), thrombus volume decreased (3.0%, IQR 1.0%-4.6%). Total aneurysm volume remained relatively constant (1.3%, IQR 0.4-1.9%). Changes in lumen volume were inversely correlated with changes in thrombus volume (r = -0.73; p = 0.001). CONCLUSION: In-vivo thrombus compressibility varied from patient to patient, and this variation was irrespective of aneurysm size, pulse pressure, and thrombus volume. This suggests that thrombus might act as a biomechanical buffer in some, while it has virtually no effect in others. Whether differences in thrombus compressibility alter the risk of rupture will be the focus of future research.

Incidental finding of malignancy in patients preoperatively evaluated for aneurysm wall pathology using PET/CT.

Preoperative positron emission tomography/computed tomography (PET/CT) was performed in 26 consecutive patients considered fit for aneurysm repair. Besides information on aneurysm wall pathology, PET/CT identified 6 patients with concomitant malignancy. As a result of this coincidental finding, the operation was postponed in 2 patients and cancelled in 1. Although previous studies have shown that PET/CT might affect patient selection based on aneurysm wall inflammation, our preliminary results show a big impact on patient management as a result of the sensitivity of PET/CT for detecting malignancy. Future larger studies are warranted to investigate the effect and cost effectiveness of routine PET/CT in abdominal aortic aneurysm (AAA) patients.

In vivo imaging of abdominal aortic aneurysms: increased FDG uptake suggests inflammation in the aneurysm wall.

PURPOSE: To study the potential of integrated positron emission tomography and computed tomography (PET/CT) to identify aneurysm wall inflammation. METHODS: The level of F18-fluorodeoxyglucose (FDG) uptake was studied in aneurysmal and normal-sized aortas of 34 male patients [17 with abdominal aortic aneurysm (AAA) and 17 age-matched controls] identified in a database of 278 consecutive patients evaluated for staging of primary lung cancer. The maximal standardized uptake value (SUV) was calculated to quantify FDG uptake in the AAA wall. RESULTS: AAAs showed significantly higher FDG uptake than the normal-sized aorta in age-matched controls (SUV 2.52+/-0.52 versus 1.78+/-0.45, respectively; p<0.001). The level of FDG uptake did not correlate with maximal aneurysm diameter (r=0.09; 95% CI -0.42 to 0.56; p=0.7). CONCLUSION: FDG-PET/CT is a promising technique to identify inflammation of the aneurysm wall. Irrespective of aneurysm diameter, asymptomatic AAAs show more FDG uptake and more inflammatory activity in the wall than the non-dilated abdominal aorta of sex/age-matched controls. Future studies will be directed at the predictive value of increased FDG uptake for aneurysm wall strength, rupture risk, and the utility of FDG-PET/CT in assessing the effect of medical interventions.

Discontinuous, staccato growth of abdominal aortic aneurysms.

BACKGROUND: To evaluate whether abdominal aortic aneurysm (AAA) growth in individual patients can be characterized as continuous or discontinuous (staccato). STUDY DESIGN: From 1996 to 2002, 609 patients presented with unruptured AAAs. Of these, 278 underwent prompt repair and 331 were observed. In this study, we included 52 patients (16% of the latter group) who had at least four CT scans and were observed for 18 months or longer without any intervention. AAA growth was defined as any increase in diameter of >/= 3 mm over any observation period(s). AAA nongrowth was defined as absence of growth for at least 6 months. Staccato growth was defined as at least one period of nongrowth combined with at least one period of growth. RESULTS: The 52 patients had a mean age of 75 +/- 8 (SD) years. The mean observation period was 42 +/- 20 months and the mean AAA diameter growth rate was 3.6 +/- 2.4 mm/y. Only 12 of these 52 patients (23%) demonstrated continuous growth. Staccato growth occurred in 34 patients (65%). Six patients (12%) showed no growth at all over 18 to 57 months (mean 30 months). No correlation was observed between initial diameter of AAAs and a patient's individual growth rate during the whole observation period (R = 0.04, p = 0.46). CONCLUSIONS: Individual AAA behavior is usually characterized by periods of nongrowth alternating with periods of growth, ie, staccato growth. Some aneurysms may have long periods of nongrowth. Accordingly, management decisions cannot be based on the presumption that observed growth rates of AAAs can be extrapolated to predict future growth rates.

Fate of collateral vessels following subintimal angioplasty.

PURPOSE: To evaluate the fate of collateral vessels adjacent to and within the target lesion following subintimal angioplasty (SIA). METHODS: Pre and postprocedural angiograms were reviewed for 29 patients undergoing SIA of the lower extremity arteries over a 3-year period. The number of patent collateral vessels

Endovascular abdominal aortic aneurysm repair to prevent rupture in a patient requiring lithotripsy.

Extracorporeal shock wave lithotripsy (ESWL) for urolithiasis may result in rupture of a coexistent abdominal aortic aneurysm (AAA). We report a patient who required ESWL and who had an AAA. Open surgery was precluded by morbid obesity and persisting incisional hernias after mesh repair. Endovascular AAA repair (EVAR) with bifurcated grafts was precluded by an 11-mm distal aorta. EVAR with stacked tubular AneuRx components was performed, followed by ESWL. The AAA was excluded, and the integrity and position of the endografts were not altered by ESWL.

Chlamydia pneumoniae serology: comparing a commercial enzyme immunoassay and microimmunofluorescence test in patients with cardiovascular disease.

Chlamydia pneumoniae has been associated with cardiovascular disease and the detection of C. pneumoniae antibodies has subsequently challenged many cardiovascular investigators. The micro-immunofluoresence (MIF) test is considered the gold standard for detection of C. pneumoniae antibodies, but requires a high-level of expertise for adequate interpretation. We compared an enzyme immunoassay (EIA) with a microimmunofluorescence test for the detection of C. pneumoniae IgG- and IgA antibodies in sera of 141 patients with atherosclerosis. The MIF test was read by two independent observers. The interobserver agreement of the MIF test for detection of seropositivity at various cut-off levels was good for IgG and for IgA. The intra-test agreement of the EIA was excellent for IgG and IgA. The agreement between EIA and MIF in detection of IgG- and IgA antibodies was adequate at low but not at high titer levels. At low titer levels, the sensitivity, specificity, positive and negative predictive value of EIA compared to the MIF test was sufficient. The sensitivity of the EIA increased, improving the agreement with the MIF at high titer levels by retesting sera with elevated titers at higher pre-dilutions. In conclusion, the EIA shows sufficient agreement with the MIF test in the detection of C. pneumoniae seropositivity. Therefore, the EIA is a practical alternative to the MIF in the detection of C. pneumoniae antibodies in patients with cardiovascular disease, bearing in mind that the sensitivity of the EIA depends on the antibody titer.

Chlamydia pneumoniae serology is associated with thrombosis-related but not with plaque-related microembolization during carotid endarterectomy.

BACKGROUND AND PURPOSE: Chlamydia pneumoniae has repeatedly been associated with atherosclerotic disease. Our study was designed to clarify whether this association is based on C pneumoniae-induced transformation of a stable into an unstable atherosclerotic plaque or on stimulation of hypercoagulability leading to increased thrombotic arterial occlusions by C pneumoniae infection. Transcranial Doppler ultrasonographic monitoring of the middle cerebral artery during carotid endarterectomy offers the opportunity to study, before removal of the plaque, atherothrombotic emboli dislodging from an unstable carotid plaque (plaque-related emboli) and emboli related to (excessive) thrombus formation at the endarterectomy site after removal of the plaque and restoration of flow (thrombosis-related emboli). METHODS: C pneumoniae IgA (> or =1/16) and IgG (> or =1/64) seropositivity was assessed in 53 patients with symptomatic carotid artery disease undergoing carotid endarterectomy. The removed carotid plaques were studied histologically to assess plaque instability. RESULTS: Plaque- and thrombosis-related emboli were registered in 43 patients with an adequate transtemporal window. IgA seropositivity (58%) was associated significantly with thrombosis-related embolization (P=0.030) but not with plaque-related embolization or with histological plaque instability. CONCLUSIONS: C pneumoniae serology is associated with microembolization after endarterectomy and restoration of flow. Since these microemboli represent platelet aggregations and are related to cerebrovascular complications, our data suggest that C pneumoniae infection contributes to cerebrovascular events in patients with carotid artery disease through stimulation of thrombosis.