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Import and Export of Interventional Technique

Something to Declare at the Border^_*

Scripps Clinic, Division of Cardiovascular Diseases, La Jolla, California

Key Words: chronic total occlusion • retrograde technique • procedural outcomes

As an example of the reluctance to attempt PCI for this lesion complexity, the frequency of CTOs was 4 times more common in the recent SYNTAX (SYNergy between PCI with TAXUS and Cardiac Surgery) surgical registry compared with the randomized trial (5). Nonetheless, still more than 90% of CTOs were attempted in patients randomized to PCI, and conversely, more than 30% of CTOs were not surgically revascularized for reasons that included an unsuitable distal target or simply operator's discretion (6). Thus, successful CTO revascularization by referral to bypass surgery does not occur by intention to treat alone.

Although there remains a rationale for the "late open artery hypothesis," clinical arguments for or against CTO revascularization are assisted by a less than complete evidence basis. Although limited by observational design, percutaneous CTO revascularization is supported by a remarkable consistency across several clinical trials associating procedural success with improved late-term survival compared with those patients for whom CTO recanalization was not achieved (7–11). A purpose for CTO PCI seems also reinforced by additional studies associating avoidance of CTO treatment with incomplete revascularization and its adverse clinical consequences (11,12).

Aside from the potential for improved late outcome, more immediate benefits of successful CTO revascularization include improved left ventricular function, decreased ischemic burden and associated symptoms, tolerance for future ischemic events, and possibly reduced predisposition for arrhythmic events (1). Despite the intuitive benefit of an open artery, however, no prospective randomized trial of CTO revascularization has ever been performed (or seems near), and the rationale for CTO PCI is challenged by a singular trial demonstrating no clinical benefit with revascularization of subacute total occlusions after recent myocardial infarction (13). Differences in the indication and pathophysiology notwithstanding, it is noteworthy that—unlike the clinical characteristics of patients included in the OAT (Occluded Artery Trial)—CTO patients selected for attempted PCI often represent a very different patient population, characterized by symptoms refractory to medical therapy, abnormal left ventricular function, multivessel coronary disease, and/or extensive ischemia demonstrated by noninvasive testing. Performance of CTO revascularization on the basis of these indications is also in accord with recent multidisciplinary committee recommendations regarding appropriateness of PCI in specific patient and lesion subsets (14).

In parallel with outcomes data indicating benefit after CTO revascularization and the successes of drug-eluting stents in maintaining target vessel patency is the stark reality that any potential advantage of CTO PCI is handicapped from the outset by the commonality of procedural failure, representing something more akin in magnitude to Achilles' leg than his heel. For instance, in spite of the frequency of attempted CTO PCI applying contemporary technical skills within the SYNTAX trial, procedural success was only achieved in 49% of lesions (6), and until recently, there was little indication by way of technique or technology that could seemingly improve rates of recanalization.

Apart from a variety of novel but ultimately disappointing technologies for crossing occluded coronary segments, specialized coronary guidewires remain the mainstay instrument in the CTO toolbox. Although CTO-specific guidewire technology itself has evolved considerably, a more revolutionary advancement has related to the technical skills and strategies regarding how these tools are used. In particular, the performance of sophisticated antegrade and retrograde guidewire manipulations introduced by Japanese interventionalists (15–17) and advanced throughout Asia and Europe have captivated audiences during live case presentations and have been uniformly met with a combination of intrigue, amazement, and speculation. What new complications might these novel techniques introduce? Without any standard means to describe case selection, procedural success, and safety, are these outcomes generalizable to the broader, international cardiology community with more variable experience and skill set? Altogether, how might interventionalists navigate a steep and narrow learning curve to develop these skills in a North American clinical practice with differing culture regarding risk tolerance and standards of care?

In this issue of JACC: Cardiovascular Interventions, Thompson et al. (18) report procedural outcomes among 636 consecutive patients undergoing attempted CTO percutaneous revascularization at 2 institutions. Among the 12 operators, 2 interventionalists were experienced with both antegrade and retrograde guidewire techniques compared with "antegrade only" proceduralists. Acknowledging potential for unmeasured biases that might influence case selection and procedural outcomes, the study is further limited by the absence of details regarding patient indications and clinical outcomes beyond the index procedure. Procedural outcomes were also not independently adjudicated, considering the interest in detailing as much as possible regarding angiographic and clinical adverse events related to this advanced technique; nor were standard definitions of myocardial infarction applied. Nevertheless, the salient findings are that: 1) incorporation of retrograde techniques for CTO PCI is possible in North American clinical practice; 2) retrograde CTO revascularization strategies seem to substantially improve procedural success rates compared with historical standards; 3) adverse safety events are similar between antegrade and retrograde techniques; 4) skills learned by retrograde operators also inform procedural success with the traditional antegrade approach; and 5) proficiency in the retrograde technique requires substantial learning and sustained experience.

The study by Thompson et al. (18) also suggests a model for describing systematic, measured adoption of complex procedural techniques directed toward complex anatomy. Pioneering methods may be: 1) shared through live case demonstrations, on-site didactic training and proctoring, Internet, and other media sources; 2) adopted selectively into practices; and 3) overall advance cardiovascular medicine by offering treatment options to patients previously without an alternative. The retrograde technique is 1 of many recent examples of interventional cardiologists' commitment to innovate, examine, and disseminate the practical aspects of evolving techniques so that they may be safely and effectively assimilated within the global interventional community.

As the investigators note, however, education regarding the retrograde approach requires extensive training over years rather than short term. Complexities of the retrograde technique extend well beyond guidewire manipulation (e.g., intravascular ultrasound, guiding catheter support technique), and it is likely for this reason that parallel advances in antegrade success were also observed. In part representing the effort required to learn these skills, only 2 of the 12 interventionalists performed the retrograde technique, yet all operators must be credited for submitting their individual outcomes as a quality and performance initiative within their programs.

The refinement of technique and advancing success in percutaneous CTO revascularization indicate that the pursuit of an open artery is anything but quixotic. Performance of advanced methods has in many instances overcome the historical predictors associated with CTO procedural failure (e.g., CTO length, calcification, sidebranch involvement) (16). Even so, not all CTO procedures are successful. New CTO techniques introduce new challenges and complications (e.g., collateral channel dilation and perforation). With the retrograde technique, still only approximately 75% of collateral channels may be traversed with a guidewire (16), and failure to do so is expectedly the greatest determinant of failure. Primary retrograde crossing is therefore successful in <70% of attempts without additional controlled dissection and/or antegrade wire techniques (16,17). It is uncertain then whether the retrograde approach should be considered a default for instances of failed antegrade recanalization or as a primary strategy in selected cases. And not all interventional cardiologists will learn these advanced methods. While there remains opportunity for improvement, the import of innovative techniques that might safely improve outcome in a lesion complexity termed the "last great barrier to PCI success" is welcomed.

	Acknowledgments

 
The author expresses gratitude to Dr. Christopher Buller for his editorial review.

	Footnotes

 
Dr. Kandzari has consulted for and received research/grant support from Cordis Corporation and Medtronic Vascular.

^_* Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.

^_* Reprint requests and correspondence: Dr. David E. Kandzari, S1056, 10666 North Torrey Pines Road, La Jolla, California 92037 (Email: kandzari.david{at}scrippshealth.org).

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