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Neuroradiology |
1 From the Departments of Radiology (H.H., H.A., M.T., K.H., M.H.) and Thoracic Surgery (N.K., J.F., K.M.), Sapporo Medical University, S-1 W-16 Chuo-ku, Sapporo 060-8543, Japan. Received May 21, 2004; revision requested August 4; revision received September 21; accepted October 22. Address correspondence to H.H. (e-mail: hyodoh{at}sapmed.ac.jp).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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MATERIALS AND METHODS: This study had ethics committee approval, and written informed consent was obtained from all patients. Fifty patients (38 men, 12 women; age range, 47–83 years; mean age, 67.2 years) who were scheduled to undergo thoracoabdominal aortic surgery for treatment of thoracoabdominal aortic aneurysm (n = 42) or thoracoabdominal aortic dissection (n = 8) were enrolled in the study. MR angiography was performed with a 1.5-T system by using dynamic three-dimensional fast spoiled gradient-recalled acquisition in the steady state with a bolus of contrast material and saline injection (4 mL/sec). Differences in the cross-clamping time, bypass time, total surgery time, and spinal complication rate between patients in whom the artery of Adamkiewicz was identified (group A) and those in whom the artery was not identified (group B) were evaluated with 
2 or Mann-Whitney U testing.
RESULTS: In 42 of the 50 patients (84% [group A]), at least one artery of Adamkiewicz was seen to arise from an intercostal artery. Two arteries of Adamkiewicz were identified in four of the patients (8%). The artery of Adamkiewicz could not be detected with MR angiography in eight patients (group B). The ranges of cross-clamping, bypass, and total surgery times, respectively, were 30–199 minutes (mean, 78.4 minutes ± 39.1 [standard deviation]), 30–298 minutes (mean, 96.9 minutes ± 60.0), and 135–665 minutes (mean, 354.9 minutes ± 133.9) in group A and 53–124 minutes (mean, 72.8 minutes ± 29.8), 10–124 minutes (mean, 66.0 minutes ± 41.0), and 220–405 minutes (mean, 315.6 minutes ± 68.8) in group B. Spinal complications occurred in two patients in group B but in none of the patients in group A (P < .001).
CONCLUSION: The artery of Adamkiewicz was detected in a large percentage of patients in whom there were no spinal complications, unlike the spinal complications that occurred in the patients in whom the artery was not detected.
© RSNA, 2005
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Locating the artery of Adamkiewicz on the diagnostic angiogram is the best way to determine its branching level and side of origin (4,5). The angiogram can show the artery of Adamkiewicz originating from the radicular or lumbar artery at the aneurysm or paraaneurysmal aorta. Detection of the artery of Adamkiewicz can be difficult, however, because of the various possible branching levels of the artery, its small size, the amount of time needed to obtain the angiogram, and complications that can occur during the procedure (4,5). If the artery of Adamkiewicz can be detected noninvasively before surgery, the appropriate graft placement method that includes either selective radicular arterial anastomosis or no branch anastomosis can be chosen (6,7).
Magnetic resonance (MR) angiography (6–9) and multi–detector row computed tomography (CT) (9–11) have been used in the noninvasive detection of the artery of Adamkiewicz. The detection rates are reported to be high (7–11). The question, then, is how best to use these noninvasive imaging modalities when planning surgical repair of or placement of a stent-graft in a thoracoabdominal aortic lesion to ensure spinal blood flow and prevent paraplegia and/or paraparesis. We are unaware of any prospective studies in which the usefulness of artery of Adamkiewicz detection at MR angiography has been evaluated in cases of surgical graft placement. Thus, the purpose of our study was to prospectively evaluate the MR angiographic detection of the artery of Adamkiewicz and the influence of such detection on outcome after surgical graft placement in a series of patients with thoracoabdominal aortic disease.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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MR Angiography
MR angiography was performed with a 1.5-T unit (Signa Horizon LX Echospeed or, beginning in January 2003, Signa Infinity Excite; GE Medical Systems, Milwaukee, Wis). Reconstruction of the radicular artery is considered a necessary part of aortic graft placement at our institution. Therefore, we use the L5 vertebra and the 12th rib to localize the L2 vertebra as the lower boundary of the field of view; a 20-cm field of view above the L2 vertebra is examined in each patient.
Dynamic studies involving the acquisition of oblique coronal sections along the posterior line of the vertebral body were performed by using a phased-array spine coil, a contrast material–enhanced three-dimensional fast spoiled gradient-recalled acquisition in the steady state (SPGR) sequence, and the following imaging parameters: repetition time msec/echo time msec, 5.9/2.4; flip angle, 10°–25°; number of signals acquired, two; matrix, 256 x 128; section thickness, 1.6; zero-fill interpolation (section ZIP, 4; in-plane ZIP, 512); no phase wrap; and field of view, 20 cm. A double dose of gadopentetate dimeglumine (Magnevist; Schering, Berlin, Germany)—that is, 0.2 mmol per kilogram of body weight—was injected through the antecubital vein at a rate of 4 mL/sec, followed by a 20-mL saline flush. A power injector (Optistar MR; Mallinckrodt, St Louis, Mo) was used in all patients.
After injection, a series of five consecutive MR angiograms was obtained to capture the prearterial-to–early arterial, late arterial, capillary, venous, and equilibrium phases. The imaging time for each phase was 22 seconds without a time delay. After data acquisition, images were stored as Digital Imaging and Communications in Medicine, or DICOM, data sets and displayed on a diagnostic monitor (Flexscan L365; EIZO NANAO, Ishikawa, Japan) at a reconstruction pitch of 0.4 mm.
Image Reconstruction
The acquired data sets were transmitted to a workstation (Advantage Workstation; GE Medical Systems). A maximum intensity projection (MIP) image was reconstructed by a radiology technician for each of the five phases with subtraction of the prearterial-to–early arterial phase image. The resulting five MIP images were used for double subtraction (eg, subtraction of the venous phase MIP image from the arterial phase MIP image yielded a double-subtracted arterial phase MIP image) (12). The first phase image and the resulting four subtraction images—five MIP images in total—were presented in a video format that followed the imaging time course.
Detection and Criteria
Criteria for the detection of the artery of Adamkiewicz on source and MIP images were as follows: (a) clear blood supply from the intercostal arteries or lumbar artery in the arterial phase, (b) identification of a blood vessel oriented toward the anterior spinal cord and joining the anterior spinal artery (in a typical hairpin configuration) in the arterial phase, and (c) diminishing vascular signal intensity in the venous phase.
One radiologist (H.H.) with 14 years of experience determined the branching level of the artery of Adamkiewicz according to the three criteria given above. To determine the usefulness of the double-subtraction MIP images, we determined the rate at which the artery of Adamkiewicz was detected when only the arterial phase source image was used and the rate of detection when the venous-to-equilibrium phase source, MIP, and double-subtraction MIP images were added.
Surgical Methods
Thoracoabdominal aortic aneurysms and dissections were treated by means of surgical graft placement. All graft placements were performed by an experienced vascular surgeon (N.K., K.M., or J.F., with 17, 23, or 15 years of experience, respectively) by means of partial cardiopulmonary bypass with double-lumen endotracheal tube anesthesia. After access to the left thoracic cavity and/or the left retroperitoneal space was achieved, the right femoral artery and femoral vein were cannulated in all patients. For thoracoabdominal aortic aneurysm repair, a left thoracoabdominal incision was made with circumferential division of the left hemidiaphragm.
When the artery of Adamkiewicz was present in the region of graft placement, only the intercostal or lumbar artery in the aneurysm that had been detected as the origin of the artery of Adamkiewicz was reconstructed and anastomosed to the graft. When the artery of Adamkiewicz was not present within the graft placement region, the cross-clamping level was adjusted and no intercostal or lumbar arteries were reconstructed. When the artery of Adamkiewicz had not been detected with MR angiography, conventional graft placement (involving reconstruction of all patent intercostal or lumbar arteries) was performed. The 12th rib was used as a landmark to estimate the level of origin and branching of the artery of Adamkiewicz.
Visceral and renal arteries were also reimplanted with an island cuff technique or preserved in a beveled distal aortic anastomosis. During reconstruction, selective visceral and renal perfusion with 10–12-F balloon cannulas was performed by clamping the outflow tubing to the lower extremities.
Statistical Analysis
To determine the effect of preoperative detection of the artery of Adamkiewicz, three of the authors (H.H., N.K., K.H.) together reviewed patients' surgical records to collect information for statistical comparison. Data were compared between patients in whom the artery of Adamkiewicz had been detected preoperatively (group A) and those in whom the artery of Adamkiewicz had not been detected preoperatively (group B). The 2 test was used to analyze differences in the number of aneurysms, number of dissections, number of concomitant diseases, number of reconstructed arteries, number of patients requiring cerebrospinal fluid drainage, and frequency of spinal complications between the two groups. The Mann-Whitney U test was used to analyze differences between the two groups with regard to patient age, maximum aortic diameter, cross-clamping time, bypass time, and total surgery time. Statistical software (StatView version 4.58; Abacus Concepts, Berkeley, Calif) was used for all statistical analyses. A P value of less than .05 was considered to indicate a statistically significant difference.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Forty-eight of the 50 patients (96%) recovered without paraplegia or paraparesis. Two patients in group B developed paraplegia after surgical graft placement. Five patients died within 30 days (range, 13–24 days; mean, 16.6 days) of surgery because of pneumonia (n = 2), aortic dissection (n = 1), cancer (n = 1), or disseminated intravascular coagulation (n = 1).
There were no statistically significant differences between group A and group B with regard to cross-clamping time (P = .861), bypass time (P = .303), or total surgery time (P = .649), but the frequency of paraplegia and/or paraparesis was significantly lower in group A than in group B (P < .001).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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It is now possible to detect the artery of Adamkiewicz noninvasively with MR angiography (6–9) and multi–detector row CT (9–11). With use of these imaging techniques for preoperative analysis, it is now possible to anastomose only one radicular artery. Kawaharada et al (6) reported that preoperative detection of the artery of Adamkiewicz decreased surgery and cross-clamping times by 30% compared with times in patients for whom this artery was not detected preoperatively; the incidence of paraplegia was also decreased. In the present study, paraplegia occurred only in patients in whom the artery of Adamkiewicz had not been detected preoperatively (group B). Thus, we believe that preoperative detection of the artery of Adamkiewicz may result in a decrease in postoperative spinal complications. We did not achieve a reduction in cross-clamping, bypass, or total surgery time in group A versus these times in group B. We believe the 30% reductions in surgery and cross-clamping time reported by Kawaharada et al are due more to surgical technique and expertise than to identification of the artery of Adamkiewicz. Further study is needed to confirm whether preoperative MR angiography reduces not only the frequency of spinal complications but also the surgery time.
Takase et al (10) reported that patients with a relatively short circulation time may have dominantly enhanced venous structures and that the timing of image acquisition relative to the injection of contrast material may be crucial for the successful identification of the artery of Adamkiewicz. Yoshioka et al (9) reported that continuity of the artery of Adamkiewicz from the aorta to the anterior spinal artery is relatively infrequent as visualized at MR angiography and that the major difficulty in detecting the artery of Adamkiewicz is differentiating it from spinal veins (10).
We believed that if the aortic laminar flow were maintained in patients with aneurysm and dissection, the time-triggered method could be used to detect the artery of Adamkiewicz with dynamic MR angiography. Laminar flow in aortic aneurysms, however, is not always evident (15). Thus, we used five consecutive images to cover the arterial, venous, and equilibrium phases and to detect not only the arterial phase but also the venous and delayed phases. Therefore, we were able to detect the artery of Adamkiewicz and the continuity between the artery of Adamkiewicz and the anterior spinal artery (the hairpin configuration) during the arterial phase and decreasing signal intensity of the artery of Adamkiewicz and the drainage vein during and after the venous phase. The double subtraction method was also useful for differentiating the artery of Adamkiewicz from the drainage vein in patients who had relatively faster circulations.
Some surgeons no longer consider reimplantation of the artery of Adamkiewicz to be the best treatment strategy, believing it best to rely on collateral circulation and a short aortic cross-clamping time (16). Kieffer et al (17), who conducted an angiography-based study, reported that the artery of Adamkiewicz was visualized by means of anastomotic circulation in only 25% of almost 400 patients, and a relatively low incidence of paraplegia and/or paraparesis in patients who underwent surgery for thoracoabdominal aortic aneurysm has been documented (18).
In the present study, two patients in whom we did not detect the artery of Adamkiewicz preoperatively had postoperative paraplegia. No spinal complications occurred in patients in whom the artery of Adamkiewicz was detected preoperatively. We believe that preoperative detection of the artery of Adamkiewicz may influence decision making in securing spinal blood flow, may minimize the number of reattachments of intercostal or lumbar arteries, and may minimize the period of hypotension. Patients in whom detection of the artery of Adamkiewicz is difficult may be at high risk for spinal ischemia during surgery. Even allowing for differences among individuals, we believe that the artery of Adamkiewicz is responsible for supplying blood to the spinal cord. It is unclear whether a hypotensive event, failure to reanastomose the necessary collateral vessels, or some other phenomenon might lead to postoperative spinal complications. Further investigation is needed to determine which factor most affects the occurrence of postoperative spinal complications.
Heinemann et al (4) observed artery of Adamkiewicz branches outside the T8 through L2 level in one of 30 patients. Koshino et al (19) examined 102 cadavers and found that the artery of Adamkiewicz frequently (90.2%) originated at the T8 through L1 level, whereas it originated at T5 through T7 in 6.9% of cases and at L2 in 2.9% of cases. We examined only 50 patients with MR angiography and identified the artery of Adamkiewicz in 42; in no patient did the artery of Adamkiewicz originate at the L1 or L2 level. We evaluated the aortic replacement level (20 cm above L2) and anastomosed the radicular artery to prevent spinal ischemia in all patients.
Svensson (3) noted that successful reattachment of segmental intercostal or lumbar arteries from T7 to L1 is important for reducing the risk of paralysis. Thus, L2 was suitable as the lower boundary for detecting the artery of Adamkiewicz, and the branches above or below our determined level were considered not to pose a risk.
The detection rate for the artery of Adamkiewicz with use of multi–detector row CT is 68%–90% (9–11). We believe that artery of Adamkiewicz data yielded by multi–detector row CT may also influence the choice of surgical procedure and decrease the number of postoperative spinal complications. In our present series, two patients (4%) had renal insufficiency preoperatively, and one of these patients required hemodialysis. Okada et al (20) reported that contrast agents that contain a gadolinium chelate can be used in patients who require hemodialysis after the examination. Therefore, to prevent renal damage in such patients, it is advantageous to use MR angiography to detect the artery of Adamkiewicz.
In the present study, the spinal complication rate was 4% overall but was 25% in patients in group B (patients in whom the artery of Adamkiewicz was not detected preoperatively). We chose conventional graft placement for these patients, and there was no significant difference between groups A and B with regard to patient characteristics or intraoperative conditions. It may be that, as long as we use conventional graft placement techniques, the rate of spinal complications will not decrease even if preoperative artery of Adamkiewicz imaging with MR angiography and multi–detector row CT is performed. Laschinger et al (21) reported that direct noninvasive monitoring of spinal cord motor function could be performed by evaluating motor-evoked potentials during aortic occlusion. Thus, if we use such evaluation in patients in whom the artery of Adamkiewicz cannot be detected preoperatively, we may eliminate the occurrence of spinal complications.
There were several limitations to our study. First, we used a 1.5-T MR unit, and each fast SPGR session lasted about 20 seconds. We might have achieved higher spatial resolution and shorter imaging times by using a higher magnetic field strength. Second, our study group included only patients who were to undergo elective surgery because we could not use MR angiography in emergent cases. Third, we did not perform a power analysis but enrolled 50 consecutive cases. A randomized trial, if feasible, would further clarify the usefulness of preoperative detection of the artery of Adamkiewicz.
On the basis of the large percentage of patients in whom the artery of Adamkiewicz was detected with MR angiography and the lack of spinal complications in these patients, we conclude that MR angiography may be particularly useful for detecting the artery of Adamkiewicz and that such detection may prevent spinal complications in patients who undergo graft placement for thoracoabdominal artery disease.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Abbreviations: MIP = maximum intensity projection • SPGR = spoiled gradient-recalled acquisition in the steady state
Authors stated no financial relationship to disclose.
Author contributions: Guarantor of integrity of entire study, H.H.; study concepts and design, H.H., N.K.; literature research, H.H.; clinical studies, H.H., N.K., H.A., M.T., K.H., J.F., K.M.; data acquisition, H.H., N.K., J.F., K.M.; data analysis/interpretation, H.H., H.A., M.T., K.H.; statistical analysis, H.H.; manuscript preparation, H.H.; manuscript definition of intellectual content, H.H., N.K.; manuscript editing, revision/review, and final version approval, H.H., M.H.
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References |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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