Limb Salvage Based on the Best Access Site to Maximize Crossing of Chronic Total Occlusion (CTO) Caps at Origin and at Reconstitution

A deeper understanding of CTOs in tibial arteries was recently described by Saab et al¹ in a study designed to determine if cap morphologies analyzed via angiograms and ultrasound performed in patients with advanced peripheral arterial disease (PAD) can be used to predict the success of different interventional approaches (i.e., antegrade vs retrograde vs combined antegrade-retrograde) for the access and crossing of transverse CTOs.  

This month, Dr. Mustapha interviews Fadi A. Saab, MD, FACC, FSACI, FASE, an interventional cardiologist practicing at Advanced Cardiac and Vascular Amputation Prevention Centers in Grand Rapids, Michigan. Dr. Saab is a member of the CLI Global Society and has a special interest in CLI awareness, education, and revascularization. 

Dr. J.A. Mustapha: Dr. Saab, can you describe the different types of chronic total occlusion (CTO) caps and their characteristics?

Dr. Fadi Saab: The Chronic Total Occlusion Crossing Approach based on the Plaque Cap Appearance (CTOP) trial describes four possible combinations of proximal and distal CTO caps (Figure 1). The different combinations of caps have been assigned numbers I to IV, with higher numbers representing a hypothetical increase in lesion complexity that would render these lesions increasingly more difficult to cross from a traditional antegrade approach. To the best of our knowledge, this is the first system to classify peripheral CTOs based on the morphology of their proximal and distal caps, and to correlate CTO cap characteristics with likelihood of a successful traditional antegrade approach to cross the lesion. The clinical application of the proposed CTOP classification is of paramount importance, as it could allow operators to plan an endovascular strategy encompassing access, crossing, and treatment prior to beginning the case. An increase in crossing success translates into time savings, improved efficiency, and decreased radiation and contrast exposure. 

Dr. Mustapha: Which one of the four CTOP types is more commonly found above the knee and which is more commonly found below the knee?

Dr. Saab: Based on our experience, we found that the Type II CTO represents the most common type of occlusion within the suprapopliteal vessels. However, when it comes to infrapopliteal vessels, a combination of Type II and IV are the most notable CTOs in that space. We don’t know the reasons behind these differences. We are just starting to understand that not all CTOs are created equal.

Dr. Mustapha:  How do you identify the type of CTO caps in your patients? Do you plan your approach based on plaque morphology?

Dr. Saab: In the CTOP trial, all patients underwent a detailed diagnostic angiogram with selective angiography of the ischemic limb. In addition to defining proximal and distal CTO cap morphology via selective angiography, we utilized ultrasound to better define the cap appearance. In the CTOP trial, we were only able to utilize ultrasound in two-thirds of the cases. This is secondary to a large percentage of patients suffering from heavy calcification that limits our ability to visualize these caps via ultrasound. Ultimately, it is for that reason we strongly recommend a detailed diagnostic angiogram on all patients with CLI and especially those with infrapopliteal disease. In the CTOP trial, almost one third of CTOs were planned dual access, with both pedal and common femoral artery access started immediately at the onset of the procedure. We believe this approach of attempting and seeing what happens can be very harmful to crossing and treating these complex lesions.

Dr. Mustapha: How do you justify spending the extra time and radiation/contrast exposure in a diagnostic angiogram? 

Dr. Saab: There is a false impression that performing the intervention immediately versus a planned, staged approach is better for the patient. Here are some of the reasons that a staged approach is superior to immediate intervention:

• Most CLI patients are frail with significant comorbidities that frequently include chronic kidney disease and cardiomyopathy, limiting the amount of contrast and procedure duration. 
• Alternative access with the pedal approach and common femoral artery (CFA) antegrade approach is essential to tackling complex, multi-level lesions and CTOs involving the supra or infrapopliteal vessels. 
• Distal tibial disease and the plantar circulation should not be addressed until the physician has obtained an antegrade CFA access. This access can not be performed when conducting a traditional angiogram with runoff.

Dr. Mustapha:  Has the combination of an initial diagnostic angiogram followed by a staged intervention changed your outcomes in terms of CTO crossing rate percentage? 

Dr. Saab: The quick answer is yes. On a clinical level, limiting the amount of contrast and its duration decreases the risk of contrast-induced neuropathy and improves patient comfort and satisfaction. From a procedural standpoint, the majority of CLI patients with complex popliteal and tibial disease require both antegrade and pedal access. This is something that is not feasible during traditional diagnostic angiography.

Dr. Mustapha: When a case has previously failed and presents to you, ca you describe how you plan and execute successful crossing and treatment?

Dr. Saab: A common scenario for prior failures is poor planning by not having a detailed baseline diagnostic angiogram or other imaging modalities, especially in patients with tibial disease. It is very common that computed tomography (CT) angiography leads to erroneous labeling of tibial vessels as occluded, when in reality, these vessels are only hibernating and possibly filling via collaterals. The most common solution to such a problem is obtaining antegrade CFA access and performing selective angiography of the tibial vessels. Suddenly collaterals are highlighting vessels that were thought to be occluded or not salvageable. Another common solution is after obtaining pedal access in an appropriate CLI patient,  performing a retrograde tibial angiogram to identify tibial vessels that were previously thought to be occluded or not present. 

Dr. Mustapha: CTOs are typically referred to as having both a proximal and a distal cap. Do you think there are additional anatomical variations to this concept?

Dr. Saab: I believe there are definitely variations in the way CTOs are created. One of the biggest predictors of the need for pedal access in the CTOP trial was lesion length. The longer the lesion, the higher the likelihood of requiring pedal access. We think this is most likely related to the presence of other CTO segments between the proximal and the distal caps. Unfortunately, there are currently no imaging modalities that can corroborate this theory.

Dr. Mustapha: Despite all the evidence supporting the use of pedal access, there remains a significant resistance to adopting it. You always discuss the safety of pedal access. Is there an advantage to pedal access?

Dr. Saab: Since our early adoption of this approach, a lot of our peers have questioned the safety of pedal access. This healthy skepticism is important to maintain adequate standards for patient care. However, the issue of safety has been addressed in multiple trials, including the pedal access trial with Walker et al² and the large retrospective trial evaluating ultrasound-guided access for pedal vessels³.  These trials show there is no significant risk of complications related to pedal access, particularly when ultrasound is incorporated. We feel that the harm created by avoiding pedal access outweighs the theoretical, unsubstantiated concerns related to pedal access. With that said, we believe there are many limbs and ultimately, lives, saved by simply adopting alternative pedal access techniques in complex anatomical CTOs. 

References

1. Saab F, Jaff MR, Diaz-Sandoval LJ, Engen GD, McGoff TN, Adams G, et al. Chronic total occlusion crossing approach based on plaque cap morphology: the CTOP classification. J Endovasc Ther. 2018 Feb 1:1526602818759333. doi: 10.1177/1526602818759333. [Epub ahead of print]
2. Walker CM, Mustapha J, Zeller T, et al. Tibiopedal access for crossing of infrainguinal artery occlusions: a prospective multi-center observational study. J Endovasc Ther. 2016; 23: 839-846. 
3. Mustapha JA, Diaz-Sandoval LJ, Jaff MR, et al. Ultrasound- guided arterial access: outcomes among patients with peri- pheral artery disease and critical limb ischemia undergoing peripheral interventions. J Invasive Cardiol. 2016; 28: 259-264.

Disclosures: Dr. Saab reports he is a consultant to Bard Peripheral Vascular, Boston Scientific, Cardiovascular Systems, Inc., Cook Medical, Medtronic, Penumbra, Philips/Spectranetics, and Terumo.

Dr. Fadi Saab can be contacted at fsaab@acvcenters.com.

Dr. J.A. Mustapha can be contacted at jmustapha@acvcenters.com.