Hybrid Algorithm for CTO PCI Delivers High Success Rates, Registry Affirms

The widely used hybrid algorithm for PCI of chronic total occlusions (CTOs) creates the opportunity to achieve high success rates even when the procedures are performed outside of the most experienced centers, findings from the European RECHARGE registry show.

That approach, which involves consideration of key angiographic characteristics to select the optimal crossing strategy before the start of each case, yielded an overall procedural success rate of 86% across 17 centers in France, the Netherlands, Belgium, and the United Kingdom, lead author Joren Maeremans (Hasselt University, Belgium), and colleagues report in a study published in the November 1, 2016, issue of the Journal of the American College of Cardiology.

And that was accompanied by a low 2.6% in-hospital MACCE rate and excellent results regarding procedural efficiency, radiation exposure, and contrast management, commented Dimitri Karmpaliotis, MD, PhD (NewYork-Presbyterian Hospital/Columbia University Medical Center, New York, NY), who was not involved in the study.

He pointed out to TCTMD that the success rate achieved in this study is slightly lower than that seen in the PROGRESS CTO registry in the United States (91.3%). He attributed the difference to the fact that the European centers had varying levels of expertise—though all operators met certain criteria to be included—and the US centers were all highly experienced.

The study “adds to a large body of literature suggesting that CTO PCI is safe and effective and that it can be applied to a broader range of hospital settings, not necessarily just expert centers, with the provision that they do have at least some minimum requirement as far as training and expertise,” Karmpaliotis said.

The Hybrid Algorithm

Introduced in the past half-decade, the hybrid algorithm for CTO PCI employs four key angiographic characteristics—proximal cap ambiguity, lesion length, quality of the distal vessel, and presence of appropriate “interventional” collaterals—to guide the choice of the preferred crossing strategy before the procedure.

“The usefulness of the hybrid algorithm is not to serve as a crystal ball, to predict with 100% accuracy that the initial strategy chosen is going to be the one that is eventually successful,” Karmpaliotis said, noting that additional sophisticated and demanding techniques like antegrade and retrograde dissection and reentry are needed to achieve high success rates. “But it’s still very, very useful,” he added, “because it creates the framework . . . [needed] to be successful and alternate efficiently between the different techniques that are available.”

To assess the real-world application of the hybrid algorithm, Maeremans and colleagues examined RECHARGE registry data on 1,177 patients who underwent a total of 1,253 elective CTO PCIs between January 2014 and October 2015. Although experience varied, all operators had performed at least 25 hybrid procedures (with an annual average of 64) and were certified antegrade dissection and reentry operators.

Procedure success rates were highest among centers or operators performing more than 100 cases per year and for CTO lesions considered “easy”.

The primary strategy selected using the algorithm was most commonly antegrade wire escalation (77%), followed by a retrograde technique (17%) and antegrade dissection and reentry (7%). Those initial strategies were successful in 60% of cases, and alternate approaches were used in another 34%. Roughly three-quarters of the bailout strategies were successful.

Median procedure and fluoroscopy times were 90 and 35 minutes, and the median contrast volume was 250 mL. Those figures, as well as measures of radiation exposure, represent reductions compared with previous reports, the authors say.

Randomized Controlled Trials Needed

The study shows that the hybrid algorithm, which is used extensively in North America, the United Kingdom, part of continental Europe, and the Asia-Pacific region, “can be applied to a broader group of interventional cardiologists who are willing to undergo training and invest the time and the effort to learn the techniques,” Karmpaliotis said. Additionally, he said, it demonstrates “that preprocedural planning and studying of the angiogram is critical [and that] alternating between strategies is key to procedural efficiency, safety, and success.”

But, as has been talked about in the CTO community for years, Karmpaliotis said, randomized trials are needed. “Until now, we didn’t have enough operators with expertise to perform the procedure with high rates of success and acceptable complication rates. Now this obstacle has been overcome.”

Although there are some CTO trials either completed or ongoing—including EXPLORE, EuroCTO, and DECISION-CTO—none employs the hybrid algorithm, he said. Designing a new trial to test the approach will be a challenge, he added, because of the variety of clinical scenarios and patient subpopulations represented in CTO populations.

Nevertheless, David R. Holmes Jr, MD (Mayo Clinic, Rochester, MN), and colleagues agree in an editorial accompanying the study that randomized trials are necessary.

“Given the maturation of the field with high and increasing technical success and acceptable complication rates, performance of well-designed RCTs should be the next priority using the clinical outcomes of death, myocardial infarction, quality of life, and repeat revascularization,” they write.