DISFORM Classification System Developed for Angioplasty-Induced Femoropopliteal Dissection

December 13, 2021—Based on a three-round, questionnaire-based process using the Delphi consensus methodology, Voûte et al describe the newly proposed DISFORM classification system for angioplasty-induced femoropopliteal dissection. The consensus study was published in JACC: Cardiovascular Interventions. 

The study aimed to achieve expert consensus in identifying clinical features of peripheral artery dissection and subsequently develop a comprehensive angiographic classification system.

Questionnaires were distributed via online software and/or email between April 2020 and January 2021. The panel consisted of equal proportions of vascular surgeons, interventional cardiologists, and interventional radiologists and a smaller sample of vascular medicine specialists from multiple regions. 

In the first round, a committee (2 vascular surgeons, 2 cardiologists) listed potential features of angioplasty-induced dissection of the femoral and popliteal arteries that may predict adverse clinical outcomes, defined as acute target lesion failure within 24 hours or early restenosis at < 6 months.

In round 2, the Delphi panel was presented with those features listed in round 1 and asked to score them for their predictive value toward the adverse outcomes, with a score of 1 representing no predictive value and 9 the strongest predictive value. A mean score of ≥ 6 was deemed significant panel consensus, with at least 70% of scores within a 3-point bandwidth. The most predictive features and preferred methods for determining morphology and flow impairment were used in round 3.

In round 3, all possible combinations of factors determined in round 2 were presented as a graphical illustration and an angiographic image (when available). Panelists were asked a single question: “Would you treat this dissection with an additional scaffold (eg, tack or stent placement)? Possible answers were, “No, I would leave it,” “Yes, I would scaffold,” and “I believe this scenario does not exist in real life.” A consensus of > 80% was considered an absolute recommendation to use a scaffold, and > 50% to 80% was considered a moderate recommendation. Conversely, > 20% to 50% was considered a moderate recommendation not to use a scaffold, and ≤ 20% was consensus not to scaffold. 

Each round had a 100% response rate. Eight features were chosen by the executive committee in round 1: (1) reduction in luminal diameter, (2) dissected artery length, (3) multiplicity of dissections, (4) contrast extravasation, (5) spiral shape, (6) double lumen lucency, (7) degree of flow, and (8) translesional pressure gradient. In addition, three methods of measuring flow impairment were suggested: (1) comparing flow through the dissected target artery to flow in the profunda femoris collateral vessels (same angiogram), (2) measuring the time for contrast filling and washout, and (3) using a flow grading system model modified from the thrombolysis in myocardial infarction (TIMI) flow grading system, which was redefined for the peripheral arteries as the flow limitation in peripheral intervention (FLIPI) grading system.

In round 2, the panel considered diameter reduction ≥ 50%, flow impairment, and spiral shape predictive of acute failure. For early restenosis, the same three factors plus length ≥ 2 cm, translesional pressure reduction, and multiple dissections were considered predictive. Most (53%) of the panel preferred the FLIPI method for assessing flow impairment, and there was consensus that real-time cine angiography was the best modality. For translesional pressure gradient, there was no consensus on what signified a pressure drop; thus, this was excluded from the classification system.

For round 3, of the eight features originally listed, diameter reduction ≥ 50%, length ≥ 2 cm, number of dissections, and spiral shape were chosen for the model. Scaffolding was recommended if the diameter reduction was ≥ 50% (100% of panelists), the dissection had a spiral shape (73%-100%), had severe flow reduction (FLIPI grade 2 or 3; 93%-100%), or if there were multiple dissections ≥ 2 cm (65%-100%). 

The final classification system, termed DISFORM, incorporates the features identified in the consensus study (diameter reduction [D], spiral shape [S], flow impairment [F], morphology [M]) and is designed as a descriptive tool to facilitate discussion around treatment options and prognosis. Morphologic and pathophysiologic features are reported as D_XS_XF_XM_X (Table 1). Four DISFORM dissection types (I-IV) are then defined based on severity, which is intended as a tool for grading in clinical trials, noted the investigators.