Abstract
The success of bypass grafting to arteries of the lower leg depends greatly on the accurate identification of suitable distal vessels. Contrast angiography has been the conventional reference standard for preoperative vascular imaging of the lower extremities. It clearly defines the anatomy of the aorta, its branches, and the peripheral arteries and thus provides an accurate map of inflow and outflow vessels to plan therapeutic interventions, such as bypass grafts and angioplasty. In the past, contrast angiography was the only nonoperative, reliable, and accurate diagnostic modality used by vascular surgeons and interventional radiologists in planning therapeutic procedures for patients with lower-extremity arterial disease. However, conventional contrast angiography has definite risks and limitations.
23
It has an overall minor and major complication rate of approximately 8%, with a risk of severe contrast reaction varying from 0.04% to 0.22%.
11,13,15,25,26
Moreover, conventional contrast angiography fails to identify all patent runoff vessels in approximately 70% of patients with severe occlusive peripheral vascular disease.
12,18,21,22
Given that 29% of our patients show evidence of baseline renal insufficiency, contrast-induced worsening of renal function
11,13
has also been an issue of serious concern.
Magnetic resonance angiography (MRA) is an alternative, noninvasive imaging modality that avoids the complications of arterial puncture, eliminates the risk of contrast-induced renal failure, and has higher sensitivity than contrast angiography in the identification of patent distal vessels in patients with severe peripheral arterial occlusive disease.
9,17
MRA is as accurate and reliable as conventional contrast angiography in the preoperative imaging of inflow vessels
10
and the preoperative grading of stenosis severity in peripheral arteries.
14
MRA can accurately identify patent runoff vessels not visualized by conventional contrast angiography.
7,17
More importantly, results of bypasses performed to these “angiographically occult” runoff vessels are similar to those of bypasses performed to vessels detected by conventional contrast angiography.
7
The recent addition of the non-nephrotoxic contrast agent, gadolinium, has further improved the accuracy and expanded the available applications of MRA.
2,8,16,19,20,24
Magnetic resonance angiography is a cost-effective,
6,27
outpatient, noninvasive technique that, if properly performed and interpreted,
23
can be sufficient for planning peripheral bypass procedures.
2,6
Although many technical and practical limitations remain to be solved before the widespread acceptance and application of MRA, some centers have already replaced conventional contrast angiography with MRA in the preoperative evaluation of patients with peripheral arterial disease.
1,2,4,5
