Bypass Surgery vs Stents: The Rematch

There’s been a lot in the news lately about the relative benefits of coronary artery bypass surgery (CABG) and angioplasty/stenting (for the purpose of this blog post I’ll use the abbreviation PCI for percutaneous coronary intervention, the term we use to encompass all the fancy plumbing procedures my interventional colleagues perform).  I say “a lot in the news” with the acknowledgment that any story about cardiac health represents no more than a blip on the radar of the overall news cycle—on the same day that two articles about the heart appear there are probably a hundred reporting on the latest attire of the pop-diva-of-the-week.

The latest headlines to which I refer raised questions about the value of PCI in patients with coronary artery disease when compared to CABG, with the suggestion that PCI may not be as valuable as we had previously thought.  Apparently, I wasn’t the only one paying attention to the front page of the Omaha World-Herald as an elderly patient of mine asked about this news when he came to see me a few days later.  Over the last decade he had taken several trips to the cath lab and was disturbed by the report’s insinuation that patients commonly receiving stents might be better served by being referred for CABG.  I tried to explain that his particular set of coronary blockages were relatively simple and he had been well served with PCI, but when he continued to appear confused I finally asked him to clarify his question.  He paused briefly, then asked “What would it take to have my stents removed and do bypass surgery instead?”

As most of you know, PCI is a procedure that opens a blocked coronary vessel without ever opening the chest.  We take advantage of the fact that arteries in the legs and arms lead directly to the coronary arteries in the chest.  Catheters and stents can be easily passed from the leg to the heart without leaving a single mark on the chest wall.  CABG, on the other hand, is a major surgery that relies on direct visualization of the coronary arteries to repair them.  “Direct visualization” is a surgical term for cutting the chest cavity open and exposing the heart to the utensils of the cardiac surgeon.  The patient is left with a scar down the front of the chest large enough to serve as a Halloween costume accoutrement.

Over the course of the last two decades doctors have been turning more and more to PCI to treat coronary narrowing and the number of CABG cases has consistently trended downward.  The recent headlines suggest that perhaps this trend needs to be reversed.  On the surface the casual reader might conclude that the pendulum of PCI revascularization has swung too far and that our medical schools need to start training more cardiothoracic surgeons.  A closer understanding (one that I hope I can convey in this post) may show you this startling news isn’t really much news at all.

The impetus for the recent debate is the announcement of the results of the SYNTAX trial, a research study that compared PCI against CABG in patients with relatively complex coronary artery disease.  The results of this study suggest that the more invasive CABG—despite its longer and more painful recovery and increased risk of stroke—is actually a better fix in the long run than the relatively simple PCI (for which the patient typically stays in the hospital only one night).  To put this in perspective let’s look at the history of these two competing therapies.

Years ago the only recourse we had for any coronary blockage was CABG, a surgery developed 50 years ago.  In the mid-1980s the science of coronary angioplasty became successful enough that doctors were turning to this procedure for uncomplicated single-vessel coronary narrowing.  The main problem we faced with angioplasty, though, was the fact that blood vessels, after being expanded by the balloon, attempt to heal their inner wall by growing new cells (technically, smooth muscle cells) to line the interior of the expanded blockage (a process called restenosis).  In about 30% of cases this new growth continued to the point where the vessel choked itself off, resulting in the need for surveillance angiograms and frequent repeat angioplasty.

Along came the technology of stents.  These small metal coils compress the vessel outward and lessen the likelihood of significant restenosis.  The wide-spread use of stent placement led to a precipitous decline in the number of CABG surgeries performed in this country as more patients enjoyed the luxury of a quick and easy repair in the cath lab.  Even with stents, however, restenosis remained a troublesome problem that prevented cardiologists from safely opening blockages located in higher-risk regions of the coronary anatomy.

In 1996 the BARI trial was published.  This expansive study provided guidance to us as to what types of patients are best served with PCI and who should be referred on for CABG surgery.  Anyone with blockages in all 3 major coronary vessels, those with diminished ejection fraction (ventricular strength), diabetic patients, and those with narrowing in the left main coronary artery (the most important of the coronary vessels) should all be taken to the operating room rather than the cath lab.  The general idea was that these patients wouldn’t survive a complication in the cath lab or restenosis of even the most expertly placed stent.

A few years back someone got the bright idea to imbue the metal of the stent with a chemical (actually a drug borrowed form the cancer chemotherapy world) that inhibits growth of smooth muscle cells into the lumen of the artery.  The initial reports of the success of the drug-eluting stents (DES) were astounding—the rate of restenosis was cut from about 15% to less than 1%.  Now that these stents are used more broadly we know that they are not as perfect as they initially seemed, but they’re clearly successful at cutting the rate of restenosis and improving long-term success of PCI.

Of course, the interventional cardiologists, now armed with a tool that potentially allows them to encroach further into the world of complex coronary blockage, start to wonder if the new DES technology might make CABG obsolete in even the most complex patients.  The makers of the new stents eagerly jumped into the debate and funded the now-completed SYNTAX study in an attempt to broaden the purview of PCI to those patients previously ruled off-limits by the BARI study.  SYNTAX compared PCI with DES to standard CABG in patients with 3-vessel coronary disease, narrowing of the left main coronary artery, and those with diminished ejection fraction.  If this study had proved positive it would have been a bonanza for patients hoping for a less invasive therapeutic option (as well as for the companies who produce the costly stents).

In the end, the SYNTAX study showed that the findings of the previous BARI study still merit attention.  Patients with high-risk coronary disease will still do better and survive longer with CABG than with PCI despite the use of the more effective drug-coated stents.

In my mind (and in the minds of my interventional colleagues with whom I’ve discussed this subject) the big news about this latest revelation is that it’s really not news at all.  What we’ve found is that a promising new technology cannot be applied as widely as we had hoped and that the system we currently use to decide how to approach coronary narrowing (the longstanding guidelines of the BARI study) is still valid.  In other words, these results simply reinforce the manner in which we already practice this branch of medicine.

So, for now, there will be no vast overhaul of the system, no grand rollback of PCI, and really not much controversy.  And, of course, I’ll have to tell my patients that I regretfully won’t be scheduling their stent extractions anytime soon.