Abdominal Aortic Aneurysm Morphology in Candidates for Endovascular Repair Evaluated with Spiral Computed Tomography and Digital Subtraction Angiography

Purpose:

To analyze the morphology of abdominal aortic aneurysms (AAAs) and to study the usefulness of spiral computed tomography (CT) versus digital subtraction angiography (DSA) in the evaluation of patients for endovascular repair.

Methods:

Of 133 AAA patients (120 men, mean age 67 years, range 52 to 84) evaluated preoperatively with CT imaging, 77 endograft candidates (68 men) were also assessed with intra-arterial DSA. Arterial parameters were measured on axial CT scans and angiographic films for comparison.

Results:

Mean maximum AAA diameter was 58 ± 11 mm (range 39 to 95). Aneurysmal neck diameter was consistently smaller on DSA than on CT (20.7 ± 3.6 mm versus 23.0 ± 3.5 mm, p < 0.0001). The distance from the most distal renal artery to the aortic bifurcation was longer on angiography than on CT (mean difference 10.0 mm, p < 0.0001). There was a positive correlation between the maximum AAA diameter and the AAA length (r = 0.49, p < 0.0001) and an inverse relationship between the neck length and the neck diameter (r = −0.36, p < 0.0001). No correlation was found between the maximum AAA diameter and maximum iliac diameter, angulation, or length.

Conclusions:

AAA anatomy varies widely and independently of the aneurysm size. Therefore, the maximum size of the aneurysm is a poor predictor of whether or not an aneurysm is suitable for endovascular repair. The discrepancy between angiographic and axial CT measurements suggests that neither alone is sufficient as a preoperative imaging technique when evaluating a patient for an endovascular graft procedure.

Spiral CT Angiography versus Aortography in the Assessment of Aortoiliac Length in Patients Undergoing Endovascular Abdominal Aortic Aneurysm Repair

Purpose:

To compare measurements of aortoiliac length obtained with spiral computed tomographic angiography (CTA) and aortography in patients undergoing endovascular aneurysm repair.

Methods:

The distances from the lower-most renal artery to the aortic bifurcation and from the aortic bifurcation to the common iliac artery (CIA) bifurcation were measured using both CTA and aortography in 108 patients with abdominal aortic aneurysms.

Results:

The level of agreement between CTA and aortography was high, with 69% of aortic and 76% of iliac measurements within 1 cm and > 90% within 2 cm of each other. Mean differences were −0.35 ± 1.20 cm and 0.25 ± 1.10 cm, respectively, for aortic and iliac lengths. Aortography overestimated renal artery to aortic bifurcation length in comparison to CTA (p = 0.003), particularly in patients with large aneurysms (> 6.5 cm) and lumen diameters > 4.5 cm (p < 0.0001). Measurements of CIA length were shorter by aortography than CTA (p = 0.02).

Conclusions:

There is a high level of agreement between CTA and aortography in the measurement of aortoiliac length, but aortography overestimates renal artery to aortic bifurcation length in patients with large-diameter aneurysms and wide aneurysm lumens. CTA is sufficiently accurate in the majority of cases to be used as the sole basis for the construction of endovascular grafts.

Multidetector CT Angiography Versus Digital Subtraction Angiography for Aortoiliac Length Measurements Prior to Endovascular AAA Repair

PURPOSE

To assess observer variation between calibrated-catheter digital subtraction angiography (DSA) and software-enhanced multidetector computed tomography angiography (CTA) in measuring vessel length prior to endovascular aortic aneurysm repair (EVAR).

METHODS

Thirty patients (25 men; mean age 65 years, range 61-85) scheduled for EVAR underwent CTA in 4x2-mm collimation using advanced vessel analysis software. CTA measurements were performed twice by 2 blinded readers in random order with at least a 4-week interval between readings. Nine patients were found unsuitable for endovascular repair after the CTA, so DSA was performed in 21 patients for morphometric evaluation of the abdominal aorta and the iliac arteries. The following segments were measured: H1 (aneurysm neck), H2 (lower renal artery to distal aspect of the aneurysm), H3 (lower renal artery to aortic bifurcation), and H4a/H4b (lower renal artery to iliac bifurcations). Length measurements on DSA were made by (1) following the catheter path in the aortic lumen and (2) dividing tortuous vessel anatomy into segments and measuring each segment along an idealized centerline. Addition of the various segments allowed comparison with data obtained from CTA measurements.

RESULTS

CTA was performed with good intraobserver agreement for all length parameters except H3 in reader 2 (p<0.05). While good interobserver agreement was demonstrated for CTA over long aortoiliac distances (H4a, H4b), higher interobserver agreement was obtained with DSA for shorter segments (H1, H2). Considerable differences were observed between CTA and DSA for the lengths H2 and H4b.

CONCLUSIONS

CTA produces better intra and interobserver correlations in measuring vessel length than DSA. It has the potential to replace DSA as an imaging method before EVAR.

Intravascular ultrasound assessment of iliac stent procedures

PURPOSE

To determine whether intravascular ultrasound (IVUS) is more sensitive in identifying incomplete stent deployment or mechanical disruption compared to angiography.

METHODS

Over a 9-month period, 44 patients (25 men; mean age 63 years, range 36-88) treated for common or external iliac artery stenoses with balloon angioplasty and stenting underwent IVUS interrogation following completion arteriography.

RESULTS

One hundred nine stents were deployed in the 44 patients. Of these, 29 (27%) stents (in 45% of patients) were found by IVUS to be incompletely deployed or to have an associated mechanical disruption despite a normal completion arteriogram. Further treatment (repeat dilation or additional stenting) was performed in 28 cases; 1 hemodynamically insignificant dissection was not treated. Twenty-six (93%) of these interventions were successful as determined by IVUS; 2 underexpanded stents did not respond to redilation.

CONCLUSIONS

Incomplete stent deployment or mechanical problems associated with stenting were common in this study, occurring in nearly half of the patients. IVUS has clinical utility in identifying incomplete deployment or mechanical problems in stents with an increased sensitivity compared to contrast angiography.

Can preoperative spiral CT scans alone determine the feasibility of endovascular AAA repair? A comparison to angiographic measurements

PURPOSE

To determine whether computed tomography (CT) alone can be used for excluding patients from endovascular repair for abdominal aortic aneurysms (AAA).

METHODS

Among 71 patients evaluated for endovascular AAA repair using spiral CT imaging and angiography, 31 were selected who had both studies performed within 6 months of each other using a graduated measuring catheter or guidewire. Measurements of aneurysm neck diameter, neck length, and infrarenal aortic length were made from the CT and angiographic images using handheld calipers with calibration markers as guides. Infrarenal aortic length and neck length were determined from CT images by multiplying the width of the cuts by the number of slices between the lowest renal artery and the aortic bifurcation or the top of the aneurysm, respectively.

RESULTS

CT neck diameter measurements differed significantly from the angiographic dimensions (6.3 +/- 5.1-mm mean difference, p < 0.001). In the majority of patients (25, 81%), CT neck diameters were larger (mean 7.3 +/- 3.8 mm). The mean difference in neck length measurements was 0.5 +/- 15.9 mm (p = NS). Twenty-two (71%) patients had aortic length measurements that were longer on the angiogram (mean 15.4 +/- 17.2 mm, p = NS). Five patients who would have been excluded as candidates based on overestimated CT neck diameter measurements subsequently underwent successful endovascular aneurysm repair.

CONCLUSIONS

Considerable discrepancies exist between preoperative neck diameter and infrarenal aortic length measurements obtained from CT scans and angiograms used to evaluate candidates for endovascular aortic aneurysm repair. CT alone may not be adequate for predicting the feasibility of endovascular AAA repair.

Abdominal aortic aneurysm morphology in candidates for endovascular repair evaluated with spiral computed tomography and digital subtraction angiography

PURPOSE

To analyze the morphology of abdominal aortic aneurysms (AAAs) and to study the usefulness of spiral computed tomography (CT) versus digital subtraction angiography (DSA) in the evaluation of patients for endovascular repair.

METHODS

Of 133 AAA patients (120 men, mean age 67 years, range 52 to 84) evaluated preoperatively with CT imaging, 77 endograft candidates (68 men) were also assessed with intra-arterial DSA. Arterial parameters were measured on axial CT scans and angiographic films for comparison.

RESULTS

Mean maximum AAA diameter was 58 +/- 11 mm (range 39 to 95). Aneurysmal neck diameter was consistently smaller on DSA than on CT (20.7 +/- 3.6 mm versus 23.0 +/ 3.5 mm, p < 0.0001). The distance from the most distal renal artery to the aortic bifurcation was longer on angiography than on CT (mean difference 10.0 mm, p < 0.0001). There was a positive correlation between the maximum AAA diameter and the AAA length (r = 0.49, p < 0.0001) and an inverse relationship between the neck length and the neck diameter (r = -0.36, p < 0.0001). No correlation was found between the maximum AAA diameter and maximum iliac diameter, angulation, or length.

CONCLUSIONS

AAA anatomy varies widely and independently of the aneurysm size. Therefore, the maximum size of the aneurysm is a poor predictor of whether or not an aneurysm is suitable for endovascular repair. The discrepancy between angiographic and axial CT measurements suggests that neither alone is sufficient as a preoperative imaging technique when evaluating a patient for an endovascular graft procedure.