A chronic total occlusion (CTO) is the complete obstruction of a coronary artery, presenting a Thrombolysis In Myocardial Infarction (TIMI) 0 flow and an occlusion duration of at least 3 months. With the advancement of equipment, techniques and key indicators, the success rates of CTO percutaneous coronary intervention (PCI) have greatly improved. During CTO-PCI meetings in 2018, it was decided that the best practices surrounding this procedure should be made globally available. A total of 113 CTO-PCI experts from 56 countries were invited to participate in this collaboration.
7 key principles as best practices for CTO-PCI
- The primary indication for CTO-PCI is improving symptoms caused by myocardial ischemia. This has been shown in several observational studies and two randomized controlled clinical trials. The first was a single-center IMPACTOR-CTO trial involving 94 patients with isolated right coronary artery CTO. They were randomly assigned to CTO-PCI or optimal medical therapy only. The CTO-PCI cohort exhibited a significant reduction in ischemic burden at 12 months and improved 6-minute walking distance and quality of life.
- Dual angiography and detailed structured angiographic review is key for improving the technical success and reducing the CTO-PCI complications. This allows for clearer visualization of the CTO anatomy leading to increased understanding of lesion complexity and likelihood of success. There are 4 key angiographic parameters that must be assessed to plan CTO-PCI. This includes: the proximal cap, lesion length, course and composition, the distal vessel and collaterals.
- A microcatheter must be used for guidewire manipulation. There are many advantages to be gained by using a microcatheter. To name a few, it allows for rapid guidewire switching during both antegrade and retrograde wire manipulations. It improves both rotational and longitudinal guidewire movement precision within fluid or tissue. Finally, it allows the penetration force of the wire to be changed by modifying the distance between the guidewire tip and the microcatheter.
- There are 4 crossing strategies that are essential for successful CTO performance. They are classified according to wiring direction (antegrade versus retrograde) and whether the subintimal space is used. They include: antegrade wiring, antegrade dissection/reentry, retrograde wiring and retrograde dissection/reentry. While antegrade wiring is the most common, antegrade dissection/reentry involves entering the subintimal space and is often an unintended consequence of the former. In retrograde wiring, the occlusion is approached from the distal vessel and the guidewire advances against the flow of blood. Several algorithms are available to aide in crossing strategy selection, such as the hybrid, Asia Pacific and Euro-CTO. The decision is driven by the lesion characteristics in addition to the equipment availability and expertise.
- Adapting a new crossing strategy when progress has stalled is key for the success, safety and efficiency of CTO-PCI. When to administer a new strategy and which strategy to choose will depend on lesion characteristics, lessons learned from the original technique, available equipment and expertise. There can be many reasons to stop a CTO-PCI attempt. These include: high radiation dose, complication occurrence, large contrast volume administration, crossing failure or patient or physician fatigue. Indeed, flexibility is critical as initial crossing strategies have only proven successful in approximately 50% to 60% of CTOs.
- Dedicated CTO-PCI programs, continual physician training and rigorous outcome monitoring are associated with increased success rates. In comparison with non-CTO-PCI, there is an increased risk of complications. Having a skilled team is, therefore, even more critical. The average complication risk is approximately 3% but there is a large variation depending on the study and the lesion complexity.
- Optimal stent deployment is an often overlooked but critical parameter for successful CTO-PCI. Given the complexity and length of time required for CTO crossing, stent placement may seem more like an afterthought. However, multiple stents are often required during CTO-PCI in vessels that are calcified, diffusely diseased or negatively remodeled. Without proper care, restenosis and stent thrombosis may occur. Techniques such as intravascular imaging should be used to assess vessel size and calcification amount to aide in stent placement.
Goals and future direction for improved CTO-PCI outcomes
With these principles in place, the hope is to aide future training, improve clinical practice and overall education. The principles have already been implemented across many, experienced clinics. Those with less experience have consequently seen less optimal outcomes. This highlights the need for broader implementation as well as easy and safe CTO crossing and revascularization strategies.
Author: Catherine Sorbara
Original Article: Circulation. 2019. 140:420-433