Treatment of chronic total occlusions (CTO) produces more difficulties, angst and trepidation than any other lesion subset in interventional cardiology. Many of the difficulties stem from: difficulty engaging the occlusion, chronicity of the occlusion, plaque burden, consequences of failure or collateral loss, perforation and the inability to effectively pass the guidewire into the distal vessel’s “true lumen”. The benefits of revascularization may include improved survival, improved left ventricular systolic function and improved quality of life resulting from palliation of angina.1–8 To date, many techniques have been employed to aid in crossing CTOs. Beyond improvements in simple guidewire technology, there are several innovative devices that extend the armamentarium of interventionalists in their quest to conquer this formidable adversary. Alternative approaches and devices include the Frontrunner XP® CTO Catheter (LuMend, Inc., Redwood City, California), a blunt dissection implement that creates controlled dissection planes in the plaque, allowing the operator to then pass a conventional wire. The Safe-Steer Wire (IntraLuminal Therapeutics Inc., Carlsbad, California) utilizes optical coherence reflectometry technology to guide transit of the wire through plaque and away from the arterial wall. Lastly, alternative approaches include attempts to cross the occlusion via access to an adjoining vein9 or from the distal aspect of the occlusion and have been described in the literature.10 In the current study by Surmely et al,11 the authors describe their technique to cross CTOs using both an antegrade and retrograde technique — the CART technique — in 10 patients. This technique, which utilizes the concurrent collateralization of the distal myocardial bed as a conduit to advance a wire and then a balloon to facilitate passage of an antegrade device, is described in their paper. They were successful in all patients they treated, with no major adverse cardiac events (MACE) described at their specified endpoints acutely after the procedure or prior to discharge from the hospital. The technique described is a standard antegrade approach with a concurrent retrograde approach to the CTO. This technique of dual access tries to “create a channel” that is then dilated in the subintimal space from the retrograde wire until the antegrade wire can enter the distal vascular bed and traverse the “true-lumen”. The authors have shown this approach to be feasible for crossing coronary CTOs. Clinically, the process of distal access has been described in the coronary circulation previously10 and is often used with success in the peripheral vasculature to cross CTOs. The distal “cap” of a CTO is often softer, allowing an easier penetration to the CTO and eventual crossing of the occlusion than from the antegrade approach. Many times, the retrograde limb of the occlusion has more of a siphon to more aggressively engage the exit of the occlusion. However, the critical risk from a coronary standpoint is the loss of that specific collateral bed that subtends the occluded coronary artery, potentially leading to myocardial infarction, arrhythmia or death. The authors demonstrate excellent technique in crossing the CTO, particularly with the use of those collateral channels from alternative coronary sources. Despite using a bypass graft in one case (10% of their cases), all other cases used large-bore collaterals (either epicardial or septal). Larger collaterals can be several layers thick. Given this, selecting the appropriate channel is critical in this approach. Further, with today’s wire and balloon technology, deliverability of the balloon for subintimal dilatation can proceed to facilitate the antegrade crossing. Beyond the critical pitfall of loss of collateral beds or loss of the bypass graft, this approach, if done with a deliberate, technically sound and thoughtful approach, allows for recanalization of a CTO with few complications. This technically challenging approach provides an additional weapon in the interventionalist’s armamentarium in approaching this most difficult lesion subset. Several key limitations and caveats should be mentioned. First, because retrograde channels were used and were collaterals for the vast majority of cases shown, the inadvertent loss of these channels could be disastrous clinically. Furthermore, because many collateral beds used were “large”, one must consider their “sacrifice” should some untoward effect or occurrence develop. The risk/benefit of such a strategy must be weighed prior to embarking on such an intervention. Finally, this study has a relatively small sample size, and requires validation in a larger population. As with all approaches to CTOs, judgement, patience and skill are the sine qua non for a successful approach. Despite these limitations, the CART approach to crossing coronary CTOs does provide an additional approach and weapon in our interventional war chests to cross these most difficult lesion subsets.
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