Dissections in Peripheral Vascular Interventions: A Proposed Classification Using Intravascular Ultrasound

Abstract: Dissections following interventions in the infrainguinal arteries occur very frequently and are mostly under-appreciated on angiographic imaging. Media and external elastic lamina injury can contribute to loss of patency, and intravascular ultrasound (IVUS) can identify this type of injury. The circumference of injury also has been proposed to be a predictor of outcome. We therefore propose a classification combining depth of injury from intima to adventitia with circumference of dissection. This classification exhibits six dissection grades (A1, A2, B1, B2, C1, and C2) as seen on IVUS (the “iDissection” classification).

J INVASIVE CARDIOL 2018;30(4):145-146.

Key words: dissection, angiogram, intravascular ultrasound, peripheral vascular interventions, superficial femoral artery, popliteal artery, femoropopliteal artery

Dissections following interventions in the infrainguinal arteries occur very frequently and are mostly under-appreciated on angiographic imaging. High-grade dissections seen on an angiogram after balloon angioplasty correlate with reduced patency and increased target-lesion revascularization.¹ It is unclear, however, how various dissections seen on intravascular ultrasound (IVUS) influence patient outcomes following infrainguinal arterial interventions. A dissection circumference ≥180° on IVUS with media involvement has been deemed a “malignant dissection.”² Also, a recent pathologic study has shown that external elastic lamina (EEL) injury can contribute to loss of patency after directional atherectomy, and IVUS can identify this type of injury.^3,4 We therefore propose a classification combining depth of injury from intima to adventitia with circumference of dissection. This classification therefore exhibits six dissection grades (A1, A2, B1, B2, C1, and C2) as seen on IVUS (the “iDissection” classification) (Table 1).  

Dissections are typically classified based on angiographic findings using the coronary artery disease classification.⁵ Although this classification has been shown to correlate with poorer outcomes, particularly with higher-grade dissections (C and higher),² there are several remaining unanswered questions. For example, do all low-grade dissections (A to C) behave similarly, or are there differences among them to explain recurrence of restenosis in some but not others? An A to C dissection on an angiogram can easily be seen involving the media and even adventitia on an IVUS; both strongly correlate with loss of patency. Tepe et al⁶ demonstrated in the Thunder trial that any dissection leads to higher loss of patency with balloon angioplasty, although drug-coated balloons seem to carry favorable outcomes in these cases. There is a general agreement that D and higher dissections require scaffolding with stents or tacks because of their adverse impact on flow. However, a high-grade E dissection, for instance, can be limited to the intima, with a large plaque falling into the lumen, therefore impairing flow. Does this type of dissection post stenting or “tacking” have a better outcome than a spiral dissection that penetrates into the media or adventitia and still appears as an E grade on an angiogram? To make things even more complicated, an angiogram that shows no dissections can have numerous dissections on IVUS. These dissections interestingly can be very significant, but manage not to be visible on an angiogram, which may explain the frequent failure of good angiographic results. The imperfection of an angiogram is not just in under-estimating dissections and their severity, but also in failing to identify the presence or severity of calcium, presence or absence of thrombus, the true size of a vessel, and the actual severity of a lesion. 

There is a clear need for a classification that combines what we know so far about the importance of the circumference of dissection and the importance of medial and adventitial depth of injury. Having a standardized classification will allow us to use IVUS to understand why failure occurs post intervention. Although there are probably multiple contributing factors, the various combinations of circumference and depth as seen on IVUS need to be factored in as seen in the iDissection classification (Figure 1). Currently, the iDissection pilot study is examining the correlation between angiographic and IVUS findings post atherectomy to the presence and severity of dissections. 

This classification does not take into consideration the length of the dissection and the presence of hematoma. Hematoma receiving significant flow via ChromaFlo Imaging (Philips Volcano) may pose a higher risk than low-flow hematomas. Also, lengthy lesions may pose a higher risk of acute closure than short ones. These factors need to be considered in conjunction with the classification above. 

A large, prospective registry is needed to determine the role of the iDissection classification on outcome post infrainguinal arterial interventions. Also, the current ability to do co-registration between IVUS and angiogram should allow us a more accurate correlation between angiographic and IVUS dissections. 

References

1.    Fujihara M. Angiographic dissection patterns and patency outcomes after balloon angioplasty for superficial femoral artery disease. Presented at TCT 2017, Denver, Colorado. 

2.    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;24:367-375. 

3.    Krishnan P, Tarricone A, Ali Z, et al. Intravascular ultrasound is an effective tool for predicting histopathology-confirmed evidence of adventitial injury following directional atherectomy for the treatment of peripheral artery disease. J Endovasc Ther. 2016;23:672-673.

4.    Tarricone A, Ali Z, Rajamanickam A, et al. Histopathological evidence of adventitial or medial injury is a strong predictor of restenosis during directional atherectomy for peripheral artery disease. J Endovasc Ther. 2015;22:712-715.

5.    Rogers JH, Lasala JM. Coronary artery dissection and perforation complicating percutaneous coronary intervention. J Invasive Cardiol. 2004;16:493-499.

6.    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. 

From the Midwest Cardiovascular Research Foundation, Davenport, Iowa and St. John Hospital and Medical Center, Detroit, Michigan.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr N. Shammas reports research grants from Intact Vascular, Bard, and Boston Scientific. Mr Torey and Mr W.J. Shammas report no conflicts of interest regarding the content herein. 

Manuscript submitted February 24, 2018 and accepted March 1, 2018.

Address for correspondence: Nicolas W. Shammas, MD, MS, FACC, FSCAI, Founder and Research Director, Midwest Cardiovascular Research Foundation, 1622 E. Lombard Street, Davenport, IA 52803. Email: Shammas@mchsi.com