Novel Classification System Proposed for Aortoiliac Occlusive Disease

PROPOSED AORTOILIAC OCCLUSIVE DISEASE CLASSIFICATION

Gross anatomy
A: Aorta
C: Common iliac artery
E: External iliac artery
F: Common femoral artery 5 mm

Disease categories
s: Stenotic (> 50%)
o: Occluded
0: No significant disease

Laterality
R: Right
L: Left

ENDOVASCULAR TODAY ASKS…

Study author Phillip Puckridge, MBBS, with Flinders Medical Center and Flinders University in Bedford Park, Australia, was asked to comment on the development of the classification system and its applicability in practice.

What were the clinical needs that prompted the development of this novel classification system for AIOD?

Treatment of AIOD has changed significantly over the last 20 years. With endovascular techniques and experience developing rapidly, the majority of AIOD treatment at our institution had become predominantly endovascular rather than open surgery. As a result, the TransAtlantic Inter-Society Consensus (TASC) classification had become less relevant to our planning than which portions of the aorta or iliac arteries needed to be dealt with to achieve a good result. We needed something to help designate targets for treatment, and there was no structure or established classification system that guided treatment planning.

In comparison, the TNM classification system in cancer therapy is beautiful in its simplicity, and this system in cancer surgery guides treatment planning. We wanted to have a similar simple process classifying disease into “bite sized” pieces to plan surgery regardless of whether the treatment was open surgery, endovascular surgery, or a combination of both. Essentially, we wanted something like the TNM system to help AIOD treatment planning. Therefore, we developed this new classification system, and we have found it very useful in our own experience.

How is this classification different from existing classification systems, and how can its use support clinical decision-making?

To date, classification of AIOD was essentially through the TASC classification system. This classifies AIOD on extent of disease, particularly on whether disease is simple or complex. TASC classification was then used as a surrogate for difficulty in treatment using endovascular techniques, suggesting that with more complex disease, an open approach was preferable. As time has passed, these original premises, although useful, have become less valid, as more complex disease was able to be treated endovascularly with good results due to development of new techniques and expertise. TASC classification was designed to stratify simple through to complex disease but is not specifically classifying each arterial segment.

In comparison, this classification system is intended to be practical in nature and a help to guide surgical planning. The proposed AIOD classification system is based on each separate anatomic location within the aortoiliac segments and the extent of disease. This system classifies based on which zones of the aortoiliac segments down to the femoral arteries are affected on each side. The degree of stenosis is not the issue, but whether the arterial segment is stenosed or occluded is important to classify, as it may affect what techniques are utilized as part of a treatment strategy. The location of the disease within the artery also affects planning of procedures. For example, treating a diseased aorta to the level of the renal arteries is very different than if the disease is limited to the distal segment only. Therefore, the classification is broken down into segments within each artery to guide treatment planning. From the letter and numeric descriptors, a picture of what is needed is established.

The concept is not to state whether the disease is severe or not, but whether that segment needs to be considered to achieve successful reconstruction. The major difference in this system compared to previous classification systems is that it is designed to assist planning treatment.