This risk is particularly high when dual antiplatelet therapy is stopped. Brilakis, Banerjee, and Berger1 recently published a state-of-the-art paper on the perioperative management of patients with coronary stents. I thought it would be worthwhile to review what this paper and the American College of Cardiology (ACC)/American Heart Association (AHA) Guidelines2 tell us about this particularly vexing problem.

The problem with coronary artery disease (CAD) and non-cardiac surgery
Some patients with CAD need coronary revascularization before noncardiac surgery. Revascularization, either by coronary artery bypass graft surgery (CABG) or percutaneous coronary intervention (PCI), is thought to reduce the risk of perioperative (a period including the first few days right after surgery) myocardial infarction and death. PCI preceding surgery has become a favored methodology for obvious reasons. However, PCI using stents may engender the rare but severe complication of acute stent thrombosis, which is associated with cessation of dual antiplatelet therapy. Acute stent thrombosis is increased in the setting of an activated thrombotic cascade. Activation of the clotting cascade occurs more in patients undergoing general anesthesia than regional anesthesia. The perioperative period predisposes the patient to stent thrombosis regardless of the type of stent used. Thus, in considering the potential of stent thrombosis after noncardiac surgery, the 2 most critical issues are 1) the timing of the surgery and 2) the method of discontinuation of antiplatelet therapy.

When to operate?
The approach to limit ischemia during surgery in the patient with CAD depends on the urgency of the surgery. Patients undergoing emergency surgery which cannot wait 1 day might best be treated with beta blockers and other medical therapy regardless of the severity of CAD and ischemia. No ASA (acetylsalicylic acid, or aspirin) or clopidogrel is needed.

If the surgery can be deferred for a week but no longer, then perhaps simple balloon angioplasty without stenting (if possible) would be best. Again, after balloon angioplasty, ASA but no clopidogrel is required. If the surgery can be deferred for a month but no longer, then a bare metal stent may be best, given the ability to rapidly re-endothelialize the vessel. Clopidogrel and ASA can be stopped before surgery. If the surgery can be put off for 6-12 months, then a drug-eluting stent may be acceptable, with a lesser risk of stent thrombosis after stopping the ASA and clopidogrel.

What is the risk of acute myocardial infarction (AMI) after stent implantation?
For a bare metal stent, Kaluza et al3 reported a very high risk of death or MI early after coronary stenting of approximately 30%, with 8 of 25 patients undergoing noncardiac surgery within two weeks (14 days) of bare metal stenting and dying. In contrast, none of 15 patients who underwent surgery 15-39 days after stenting died. On the other hand, in a larger series from the Mayo Clinic4, patients undergoing surgery within two months of receiving a bare metal stent had a 4% incidence of death or acute myocardial infarction. The risk of death, MI, or stent thrombosis is lower in the Mayo Clinic study, but the risk remains present for six weeks, not just two weeks as previously suggested by Kaluza et al.3

For drug-eluting stents, McFadden et al5 reported subacute stent thrombosis in three patients undergoing gastrointestinal or genitourinary surgery late (> 300 days) after the implantation. Nasser et al6 reported thrombosis in two patients, 4 and 21 months after drug-eluting stent implantation following surgery.

Most, if not all stent thromboses were in the postoperative period and associated with the discontinuation of the dual antiplatelet therapy.

Prevention of stent thrombosis: Perioperative or postoperative
Brilakis et al recommend 5 ways to reduce the potential of acute stent thrombosis before surgery:

1) Avoid preoperative vascularization. The Coronary Artery Revascularization Prophylaxis (CARP) study7 suggested that revascularization may not necessarily be of benefit for a large number of patients without unstable coronary syndrome or high risk of ischemic features. This study was further supported by Poldermans et al8 who also found that in patients with extensive ischemia preoperative revascularization did not improve their outcome.

2) Revascularize patients without stents. Can we avoid stenting in the short term and achieve reduction of ischemia for the surgical period without the risk of stent thrombosis by performing simple balloon angioplasty alone? This approach is certainly feasible and must be balanced against the risk of coronary restenosis or abrupt occlusion during or immediately after the PCI. Revascularization with balloon angioplasty alone may be safer than stent placement, especially if the angiographic result is good and if the noncardiac surgery is planned within a 4-week period. The 2002 ACC/AHA Guidelines in perioperative cardiovascular care2 tell us that when there is uncertainty as to the timing of noncardiac surgery after balloon angioplasty, delaying cardiac surgery for a period of 6-8 weeks appears to be less optimal because restenosis will have advanced, thus leading to potential ischemia or infarction and thus delaying surgery for at least a week after balloon angioplasty has theoretic benefits.

3) Select the stent to be implanted for the timing of surgery. Does a stent type make a difference? In the practice of coronary balloon angioplasty, stenting at times cannot be avoided, either because of complexity or because of unsatisfactory angiographic outcome. Using bare metal stents is preferable to drug-eluting stents in this setting because of the more rapid endothelialization, lower risk of stent thrombosis and shorter duration of dual antiplatelet therapy until the time of surgery. Although restenosis may be more likely to develop with a bare metal stent, in-stent restenosis can be addressed with a drug-eluting stent. Clearly, the timing of surgery makes a difference. If surgery can be delayed for more than 12 months, then a drug-eluting stent may be appropriate. If the patient can wait that long, it removes any issues regarding dual antiplatelet therapy and drug-eluting stents.

4) Delay surgery until stent endothelialization. According to the ACC/AHA Guidelines2, noncardiac surgery should be delayed for at least two and ideally four weeks after bare metal stent implantation for partial or complete endothelialization. The optimal timing of surgery is unknown, but appears that it would be longer than 12 months given the existing data on timing of endothelialization and requirement for dual antiplatelet therapy.1

5) Continue dual antiplatelet therapy throughout the perioperative period. How should we manage antiplatelet therapy in the perioperative period? As a result of the issues with regard to acute stent thrombosis when dual antiplatelet therapy is stopped, confidence in endothelialization of the implanted stent must be high enough to permit this to occur. Antiplatelet strategies to minimize perioperative stent thrombosis have discussed continuation of aspirin and clopidogrel before, during and after the procedure as well as discontinuation of one of the two agents with institution of a short-acting glycoprotein IIb/IIIa receptor inhibitor and the reinstitution of clopidogrel soon after the surgery. The alternative would be to simply continue aspirin therapy, discontinue clopidogrel and restart after the procedure. There are advantages and disadvantages to each of these methodologies but no firm data to guide us.

Improving the awareness for all physicians of the catastrophic complications of subacute thrombosis (SAT) will improve the care of these patients. For a general approach for both the patient and physician team, the need to delay the elective surgery approach whenever possible after stent implantation is of paramount importance. Brilakis et al1 report in their survey of anesthesiologists that 63% were not aware of any recommendations about the appropriate length of time between stent implantation and subsequent surgical procedure and at least 30% recommended no delay or delay of only 1-2 weeks, which is insufficient for re-endothelialization of both bare metal stents and certainly drug-eluting stents. Anesthesiologists, surgeons and other physicians involved in the care of these patients should be alerted to the high risk of stent thrombosis in patients who have received coronary stents.

In summary, the risk of stent thrombosis after implantation is low when the surgery has been delayed for at least 4-6 weeks after bare metal stenting. The risk of stent thrombosis after a drug-eluting stent and surgery is poorly studied, but in general, probably should not proceed before at least 6 months, 12 if possible. If major non-cardiac surgery is planned within four weeks and certainly within two weeks with the need for PCI, one should consider coronary balloon angioplasty to relieve ischemia. If the surgery is planned for between 1-12 months, particularly if the anatomy is complex and stenting is required, selection of a bare metal stent might be preferable to a drug-eluting stent. If surgery is planned after 12 months, a drug-eluting stent is certainly an acceptable alternative.

I believe it is worthwhile for all of us to think about when to operate on patients who have had recently implanted stent and provide them with best possible outcomes through education, timing of surgery, and appropriate cessation of the dual antiplatelet therapies.