The mechanism of angioplasty is to create dissection

Figure 1: Image courtesy of Joseph Cardenas, MD
Figure 1: Image courtesy of Joseph Cardenas, MD

Percutaneous transluminal angioplasty (PTA) increases the arterial lumen by pushing the plaque outward with enough force to cause the plaque to rupture or fracture (Figure 1). Because plaque accumulates and adheres to the innermost layer of the vessel wall, the intima is also torn during inflation. As more force is applied to the lesion, the dissection can expand in multiple directions: deeper into the vessel wall (media, adventitia) and/or along the length of the vessel.

Dissections are often underdiagnosed

Figure 2: Image courtesy of Christian Wissgott, MD
Figure 2: Image courtesy of Christian Wissgott, MD

Dissections appear on angiography when contrast collects between the fractured intima and the exposed media (Figure 2). During endovascular procedures, operators use a real-time visual estimates to identify and classify post-intervention dissections. Challenges such as vessel overlap, foreshortening and non-concentric lesions can limit two-dimensional angiography. Like the plaque itself, dissections can be eccentric and misinterpreted or missed altogether if viewed from only one angle or if proper magnification isn’t used. Bone interference during angiography and small vessel caliber can also contribute to underdiagnosis of infrapopliteal dissections.

Dissections are often underestimated

While there is no established consensus on classifying peripheral arterial dissections, the National Heart, Blood and Lung Institute (NHLBI) classification for coronary arteries is often applied to the lower extremities. Six grades ranging from minor dissection (A) to total flow disruption (F) describe the severity of vessel damage.1

Click image to enlarge
Figure 3 - Bosiers M et al. J Vasc Surg 2016;64(1):109-16.
Figure 3 - Bosiers M et al. J Vasc Surg 2016;64(1):109-16.

During endovascular procedures, operators use a real-time visual estimate to identify and classify post-intervention dissections. In the Tack Optimized Balloon Angioplasty (TOBA) study, investigator-reported dissection grades were compared with the findings of the angiographic core laboratory (Figure 3). Investigators graded dissection as ≥C in 25.8% of lesions, whereas the core laboratory determined that dissection ≥C was present in 74.0%.2

This further underscores the fact that dissections are prevalent and often underestimated.

Which dissection grades matter?

While there is consensus that severe dissections result in poorer outcomes, an objective definition of “severe dissection” has yet to be made. NHLBI Type A and B dissections are generally excluded as severe dissections.  However, data demonstrates that these seemingly minor dissections still negatively impact long-term outcomes.

A retrospective by Fujihara et al3 investigated the incidence of post-PTA dissection. The overall dissection rate was 84%. Lesions with severe dissections (C-F) had a 34% TLR rate at six months. A 14% TLR rate was reported for the remaining lesions which included no dissection as well as grades A and B. Although the zero dissection group was included with grades A and B, the data reported that lesions with grade B dissections were nearly twice as likely to need revascularization than Grade A.

In the THUNDER study, Grade A-B dissections experienced similar rates of six-month target lesion revascularization (TLR) as did Grades C-E (33% and 43%, respectively). At 24 months, those rates increased to 43% for Grades A-B and 78% for Grades C-E.4

For informational purposes only. You should always consult with your doctor when seeking medical advice or considering treatment.

References

  1. National Heart, Blood and Lung Institute. Coronary artery angiographic changes after PTCA. In: Manual of operations: NHLBI PTCA registry. Bethesda, MD: NHLBI; 1985. p. 6-9.
  2. Bosiers M, ,Scheinert D, Hendriks JMH et al. Results from the Tack Optimized Balloon Angioplasty (TOBA) study demonstrate the benefits of minimal metal implants for dissection repair after angioplasty. J Vasc Surg 2016;64:109-16.
  3. Fujihara M, Takahara M, Sasaki S et al. Angiographic dissection patterns and patency outcomes after balloon angioplasty for superficial femoral artery disease. J Endovasc Ther 2017;1-9.
  4. Tepe G, Zeller T, Schnorr B et al. High-grade, non-flow-limiting dissections do not negatively impact long-term outcome after paclitaxel-coated balloon angioplasty: an additional analysis from the THUNDER study. J Endovasc Ther 2013;20:792-800.