Treatment of Chronic Total Occlusions Using Optical Coherent Reflectometry and Radiofrequency Ablative Energy: Incremental Succe

Chronic total occlusions (CTO) account for 10–15% of patients undergoing coronary angioplasty. Recanalizing CTO has been a challenge to the interventional cardiologist because of the inability to visualize the vessel lumen and/or cross the hard fibrotic plaque. Success in treating CTO using conventional angioplasty techniques has been dependent on lesion and vessel characteristics and the skills of the operator and ranged from 25–75%.^1–3 Multiple technologies have emerged to treat CTO. Specialized guidewires, blunt micro-dissection, laser and recently high frequency vibrational energy have been used with modest improvement over conventional techniques. All these new technologies are “blind” unable to “see” the true lumen of the vessel. Recently, Optical Coherent Reflectometry with radiofrequency ablative energy (Safe-Cross wire, Intraluminal Therapeutics, Calif.) was utilized to treat CTO.⁴ Using near infrared light, this guidewire system can distinguish calcified from noncalcified plaque and atherosclerotic lesions from arterial wall and display the results on a monitor. In addition, when resistance is encountered, radiofrequency ablative energy can be delivered to facilitate crossing of the fibrocalcific plaque.

See Wong, et al. on pages 54–57

In the report by Wong et al.,⁵ the authors describe their experience with the Safe-Cross wire. Among 21 patients with CTO, conventional wires were successful in crossing the occlusion in nine (43%) patients. On the other hand, the Safe-Cross wire was successful in ten out of twelve remaining patients (83.3%) in whom conventional techniques have failed. The total success rate was 90% and appears significantly more than historic controls using conventional techniques (average success 50%). The data by Wong et al.⁵ is in concordance with Ng and colleagues⁶ who have recently reported a 60% success rate in recanalizing CTO after failed conventional techniques. In addition, a recent small (n=26) randomized trial between the Safe-Cross and conventional wires in treating CTO yielded a crossing success of 85% and 62% respectively.⁷ The success of the Safe-Cross has also been seen when treating CTO across other vascular beds. Recent data from our group demonstrated a 72.7% success rate in recanalizing CTO in the peripheral vasculature following failure of conventional techniques.⁸ The Safe-Cross guidewire system appears to be effective and safe in recanalizing CTO with an incremental benefit over conventional guidewires. Steering the Safe-Cross guidewire in a vessel can be challenging because of its relatively stiff and straight wire tip. Wong et al.⁵ describes a case where an angled catheter was used to steer the guidewire. In our experience, this technique can be very effective in directing the wire tip to the intended target and increase the chance of crossing the CTO. In addition the authors describe the use of the “buddy wire” technique to enhance crossing CTO with the Safe-Cross system. Traditional use of multiple simultaneous conventional wires in crossing CTO is not unusual. Theoretically, the presence of the conventional wire in the false lumen might act as a barrier preventing the Safe-Cross guidewire from penetrating the same false channel. Finally, the investigators utilized contralateral injection of dye in 76% of their patients to visualize collaterals to the occluded vessel. Despite this effort, they noted a success rate of only 46% in crossing CTO. Using the Safe-Cross as a primary crossing modality, operators might lessen the need to do simultaneous contralateral angiography, shorten fluoroscopic time, increase overall primary success and lower complications. The cost-effectiveness of this approach needs, however, to be validated. Treatment of CTO can be very important in reducing symptoms and medications and minimizing ischemic burden. In addition, some data suggest that treatment of CTO can result in improvement in the function of the hibernating myocardium supplied by the occluded vessel with subsequent increase in ejection fraction and possibly better long-term prognosis.^9–11 Currently symptoms and the burden of ischemia are major driving forces in the treatment of CTO. Also, a recanalized vessel might become an important source of collaterals to the rest of the coronary vasculature. With the incremental success offered by the Safe-Cross over conventional wires in the treatment CTO, interventional cardiologists can now tackle a very difficult lesion subset with an apparent high success rate. Finally, early data suggest that the high rate of restenosis seen on follow-up with treatment of CTO^12,13 is likely to be reduced significantly with the use of drug-eluting stents.¹⁴ With the acute crossing success of the Safe-Cross guidewire and the low restenosis rate of the Cypher stent, treating CTO with bypass surgery is rapidly becoming a practice of the past.