Experts Debate Future of Left Main Disease: More PCI or More Surgery?

Reed Miller

March 02, 2011

March 2, 2011 (Washington, DC) — Now that the professional guidelines regard stenting as a reasonable option for some patients with left main coronary disease, interventionalists expect to treat an increasing number of these patients, while surgeons are trying to maintain their share of this difficult patient population.

During a formal debate on the future of left main revascularization here at CRT2011, the Cardiovascular Research Technologies conference, conference chair Dr Ron Waksman (Washington Hospital Center, DC) argued that the portion of left main patients revascularized with PCI instead of bypass surgery will grow in the next few years. Surgeon Dr Michael Mack (Medical City Dallas Hospital, TX) argued that about 80% of these patients will continue to be treated with CABG surgery for the foreseeable future.

Recent guidelines from the European Society of Cardiology and a "focused guidelines update" from the American Heart Association/American College of Cardiology state that PCI in the left main, previously not recommended, should be considered an alternative to surgery in patients at low risk for procedural complications. The debaters agreed that this change was reasonable, but most of the debate centered on the results of SYNTAX, in which PCI failed to meet the prespecified margin of noninferiority against CABG in patients with left main coronary disease and/or three-vessel disease. SYNTAX also led to the creation of the SYNTAX score, which measures the complexity of the patients' disease. Surgery is the only option for patients with a score of 33 or higher, while patients with a score of 22 or lower are good candidates for PCI.

But, Mack pointed out, while 1800 patients were randomized in SYNTAX, another 1077 enrolled into the trial were put in a separate CABG registry, because both the surgeons and interventionalists reviewing the patients agreed they were not good candidates for intervention. "That's 59% of the SYNTAX patients that everyone agreed still should be treated with surgery," he said. "We shouldn't lose that context." Since nearly 60% of left main patients are definitely not suitable for PCI and PCI failed to beat surgery in a randomized trial of the other 40%, Mack concluded that about 80% of left main patients will still go to surgery for the foreseeable future.

In light of SYNTAX and the development of transcatheter valves, the new guidelines also recommend the creation of teams of interventionalists and surgeons who discuss the best options for the patient. Waksman said that these discussions are hastening the shift of left main patients from surgery to the cath lab. "There is a change in the paradigm. There is no more routine surgery for left main [disease]. This is over." But Mack hasn't seen much of a change in how these patients are treated as a result of these collaborations. "We have very little clinical debate about the management of these patients."

Both debaters agreed that the forthcoming Evaluation of Xience Prime versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization (EXCEL) trial will shed a lot more light on the issues of left main revascularization. As reported by heartwire , the 2500-patient EXCEL study, sponsored by Abbott, will compare PCI with drug-eluting stents vs CABG in patients with unprotected left main coronary artery disease who are considered candidates for either PCI or CABG. The three-year study's primary composite end point includes death, MI, and stroke. Target lesion revascularization will be a secondary end point. "These results will determine which way we go," Waksman said.

Race for Improved Outcomes

In SYNTAX, repeat revascularizations were higher with PCI, while strokes were more common in the CABG patients. But both Waksman and Mack argued that the SYNTAX results do not reflect the outcomes that can be expected from PCI or surgery in the future as both procedures continue to improve.

"PCI is getting simpler and better," Waksman said. "I think that we've seen that because the techniques and the pharmacotherapy have improved. We have safer procedures with more vessel predilations and mostly no need for hemodynamic support. We've learned how to use [intravascular ultrasound] IVUS for guidance . . . and we've improved the stents and have better antiplatelet therapy. And so we're getting better results."

Mack countered that surgeons are also refining their procedures. "We can make CABG better in the left main. There were some major issues with CABG that were brought up with SYNTAX." For example, he pointed out that the stroke rate of CABG patients in SYNTAX was highest in the period of 30 days to one year after surgery. "Why? Well, only 20% of the patients in the CABG group were on dual-antiplatelet therapy, and only 15% were on it one year, raising the question [of whether that is] possibly protective, especially with the 30% incidence of atrial fibrillation in the CABG group."

Also, only 15% of the CABG procedures in SYNTAX were done off-pump, and many of these patients did not undergo epiaortic scanning of the aorta for disease, Mack pointed out. The clamping of the aorta required for on-pump surgery is often blamed for strokes caused by emboli released from the aorta. "In these patients, off-pump surgery should be used. There's been concern that off-pump surgery isn't as safe in the left main, but since SYNTAX, there have been at least four series to show that it is safe in the left main," Mack said.

Commenting after the debate, interventionalist Dr Gregg Stone (Cardiovascular Research Foundation, New York, NY) said, "There's been a tremendous evolution in five years. Surgery has also improved, but I would hazard to say not as fast as PCI has improved. And I think that if SYNTAX were redone, using a little bit of common sense and reason, even with some higher SYNTAX scores, it could have been a positive study, meaning noninferiority for PCI."

Stone said that the PCI results in SYNTAX were not as good as they could have been because the interventionists had "a lot of bravado." At that time, the attitude was "we can do anything now with drug-eluting stents, we can do an all-comers trial and the worst anatomy." As a result, Stone said, too many of the cases were done as single procedures, when better results could have been achieved with staged revascularization. Also, too many interventions were completed without IVUS, which should be used to ensure optimal stent placement, or without fractional-flow reserve (FFR) imaging, which can show which lesions are not worth stenting because they aren't significantly impeding blood flow. Also, the stents and concomitant pharmacotherapy have improved since SYNTAX, he said.

Mack said that greater use of fractional-flow reserve imaging would also improve surgical results. "There's a lot of redundancy in grafts in surgery for the left main. Often, we put a graft to the [left-anterior descending] LAD [artery] and a graft to the circumflex with no lesion in between. I think in SYNTAX, we bypassed a lot of 50% lesions which, by FFR, would have been shown not be significant." He pointed out that in the LE MANS study, stent thrombosis was associated with mortality, but graft failure was not, because, Mack believes, the graft that failed was usually a redundant LAD graft that failed due to competitive flow from the [left internal mammary artery] LIMA graft that stayed open. "So rather than the concept of complete revascularization, we will move toward appropriate revascularization, and I would hypothesize, a fewer number of grafts, shorter operations, and shorter ischemic times, that will hopefully lead to better outcomes."

Despite his confidence in PCI for more left main patients, Stone reiterated the importance of interventionalists collaborating with surgeons to decide on the best course for every patient. "Patients should hear their options for most of these cases. Except for single-lesion, single-vessel circumflex disease, no case of revascularization is so straightforward and certainly no left main is so straightforward that I wouldn't want to hear about the surgical alternative."

Stone previously reported being on the advisory board for and receiving honoraria from Boston Scientific and Abbott Vascular and being a consultant for the Medicines Company. Waksman reports research support from the Medicines Company, Boston Scientific, and Medtronic and consulting for Abbott Vascular and Biotronik. Mack previously disclosed he has served as an advisor or consultant for Medtronic and Symetis.