CTA builds reputation in peripheral disease

CT angiography performed with 16-slice scanners makes a significant difference in clinical decision making about the diagnosis, treatment, and follow-up of peripheral vascular disease.

Dr. David E. Allie and colleagues at the Cardiovascular Institute of the South's Lafayette, LA, clinic performed two analyses over six months to gauge the scanners' effectiveness. The anatomic percent stenosis analysis looked at the following arteries: iliac (138), superficial femoral (130), renal (110), infrapopliteal (108), internal carotid (86), celiac (62), and superior mesenteric (62). CTA results correlated very strongly with conventional diagnostic angiography/digital subtraction angiography in the iliac, superficial femoral, and internal carotid arteries. Strong correlations were found in the renal, celiac, superior mesenteric, and infrapopliteal arteries.

The second analysis involved a questionnaire that simply asked whether physicians in 144 cases believed that multislice CTA significantly influenced clinical decision making. Respondents answered in the affirmative in 94 cases (65.3%).

Allie, the director of cardiothoracic and endovascular surgery at the clinic, said he will not perform an intervention unless the patient receives a CTA scan.

"I thought I knew everything about peripheral vascular disease until I picked up this new technology," he said.

A radiologist interprets all nonvascular CT imaging and reviews all vascular MSCTA studies. Cardiologists and surgeons also interpret each CTA.

The clinic's mostly elderly patients have other diseases besides peripheral vascular disease and can be imaged in the office from head to toe in less than 45 seconds. Diagnostic angiography carries a small but real risk of stroke, and many patients have limited vascular access. CTA overcomes these problems. The 16-slice scanners are not often affected by artifacts, an important consideration for patients who have stents, clips, pacemakers, and a lot of calcium. Three-D reconstruction and multiple views are two significant advantages, Allie said.

Physicians can see inside vessels and stents, which will become more important as carotid stenting nears approval. CTA will help determine how to enter the carotid artery and where to place the distal protection device, he said. Cardiologists at the clinic are looking inside aneurysms and placing blood pressure sensors in the aneurysm sacs after endovascular repair. MSCTA also enables them to perform calcium scoring, see soft tissue and bone, and perform occult neoplasm screening.

"We have a thoracic practice, so we deal a lot with chest malignancies. MSCTA is ideal for this," Allie said.

Allie reported on a patient who had received two renal artery stents, but his hypertension persisted. Duplex ultrasound did not reveal much because of the patient's obesity. Curved coronal reformations of CTA data showed intimal hyperplasia. CTA showed flow and stent position in the celiac and superior mesenteric arteries. Another patient, who continued to have problems after the removal of his gallbladder, underwent CTA, which revealed a very tight stenosis of the inferior mesenteric artery.

"This is a rare type of lesion that couldn't have been found as nicely any other way," he said.

Contrast-induced nephropathy is the biggest concern with the use of CTA. Most patients with a creatinine level less than or equal to 1.8 mg/dL can tolerate an intravenous dose of 100 mL of nonionic low-osmolar contrast, Allie said. Multiple protocols are available for patients with chronic renal insufficiency. A one-week follow-up of creatinine is obtained from all outpatient CTA patients.