Imaging vital for ensuring safe endovascular procedures, say Japanese physicians

The advantages of endovascular procedures are numerous, but the list of potential complications is just as long. A multidisciplinary team of researchers from Yamaguchi University School of Medicine in Japan summarized those complications, and the best way to image them, in the latest issue of RadioGraphics.

The group, made up of radiologists, surgeons, and internal medicine specialists, looked specifically at complications resulting from endovascular repair for thoracic and abdominal aortic aneurysm. Less blood loss, shorter stays in intensive care and subsequent hospitalization, and quicker recovery periods, give endovascular stent-graft implantation a certain edge over conventional open surgery, according to the authors.

But the complications range from the common, such as endoleak, graft thrombosis, and graft kinking, to rare, but generally fatal, occurrences of graft occlusion, shower embolism, colon necrosis, and hematoma at the arteriotomy site.

"Many studies show that endovascular stent-graft therapy is safe and effective…a few investigators have reported complications in the non-radiology literature, but the description of imaging findings is limited. Since some of these complications are fatal, radiologists need to instantly and accurately recognize them," they wrote.

Over a two-year period, the 49 patients who made up the study population were treated with endovascular stent-graft implantation. The stents were constructed from self-expandable Gianturco Z-stents, while the graft portion was thin-walled, woven Dacron (Ube Graft, Ube, Japan).

Follow-up imaging was done with spiral CT (Somatom Plus 4, Siemens Medical Systems, Erlangen, Germany) and 100 mL of nonionic contrast material. The imaging exams were done seven days after the procedure.

"When complications were suspected on the basis of spiral CT findings, plain abdominal radiography or digital subtraction angiography were also performed," the group explained.

Out of 49 patients, 25 experienced complications. The most common complication was leakage into the aneurysm, which can be caused by incomplete fixation of the stent-graft to the aortic wall of graft defects. Axial CT findings on the basis of configuration and location of the leak revealed the cause, the authors wrote.

However, with regard to graft kinking, axial CT images "cannot depict the shape of the stent-graft adequately, but maximum intensity projection or multiplanar reconstruction images can clearly demonstrate the graft kinking," according to the authors.

In terms of rare complications, pseudoaneurysm caused by graft infection occurred in one patient after a tapered stent-graft implantation from the aorta to the right iliac artery, and required several imaging techniques to be used. Abdominal radiography two weeks after the procedure revealed that the "occluded stent-graft at the left common iliac artery narrowed as the artery ran peripherally."

Two months later, the patient had fever, left inguinal swelling, and tenderness, and pelvic CT showed a soft-tissue attenuating area around the distal end of the occluded stent-graft. Finally, digital subtraction angiography showed pseudoaneurysm at the distal end of the occluded stent-graft in the left common iliac artery, the group said. In this case, the imaging was able to guide the emergency surgery by pinpointing the occluded stent-graft and pseudoaneurysm.

"The principle in such surgical treatment is total excision of the infected graft," the authors wrote. "A combination of administration of systemic antibiotics and surgery is necessary to obtain successful results…treatment with exclusive[ly] antibiotics is invariably fatal."

In another instance, a more extensive preprocedural CT exam may have prevented the death of a patient from a shower embolism. The 78-year-old woman had undergone preprocedural CT that showed an irregular, shaggy mural thrombus in the abdominal aorta.

During the endovascular procedure, "a guide wire and an angiographic catheter were repeatedly introduced via the brachial artery through the aortic arch to the abdominal aorta [and] the sent graft was deployed without difficulty."

Two days after the procedure, however, the patient was unconscious, and a brain CT depicted a cerebral infarction; the patient died a day later of renal failure and intravascular coagulation, they wrote.

"Shower embolism was confirmed at autopsy. We believe the shower embolism was caused by mural thrombus dispersed during the repeated introduction of the guidewire, angiographic catheter, and delivery systems. Preprocedural contrast-enhanced CT was not performed at the level of the thoracic aorta, but shaggy mural thrombus…might have been present," the authors noted.

The team concluded that spiral CT is the most efficient imaging procedure for assessing complications before and after endovascular procedures. The complex anatomy of the aorta are especially enhanced by shaded surface display, multiplanar reconstruction, and curved-planar reconstruction images.

In addition, "plain radiography and digital subtraction angiography sometimes play an important role in the detection of serious complications," they wrote.

To view the full text of this article, go to RadioGraphics, September 2000, Vol.20:5, pp.1263-1278.
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