If I told you guys that you wait 1 yr for "drug eluting stents" and continue the ASA and the plavix will be continued or discontinued based on the type of surgery, would you say I am crazy? Probably, but the recent recommendations at the Society of Cardiac Anesthesiologists is exactly that.
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Noncardiac surgery in patients with coronary artery stent: what should the anesthesiologist know?
CORONARY artery stents significantly decrease coronary restenosis and abrupt vessel closure as compared to standard coronary balloon angioplasty.14 Consequently, they are implanted in most patients requiring percutaneous coronary intervention (PCI).5 One major consideration with coronary stents is their thrombogenicity at the blood-tissue interface which may cause local thrombosis or distal coronary embolization. Those complications are associated with a 50% incidence of acute myocardial infarction (MI) and a 20% mortality rate,6 making prevention of stent thrombosis mandatory in all cases. The most effective antithrombotic strategy involves the administration of aspirin and a thienopyridine (clopidogrel or ticlopidine) for a minimum period of four to six weeks for bare metal stents and several months for drug-eluting stents, until significant re-endothelialization of the stent has occurred. With this approach, stent thrombosis within 30 days of implantation occurs in less than 1% of patients who had an uncomplicated PCI.6
In their most recent guideline update for perioperative cardiovascular evaluation for noncardiac surgery, the American College of Cardiology (ACC) and the American Heart Association (AHA) recommended a delay of at least two weeks and ideally four to six weeks between stent implantation and noncardiac surgery (e.g., four full weeks of dual antiplatelet therapy during stent re-endothelialization and two weeks for the antiplatelet effect to wear off).7 There is no prospective controlled trial to support that recommendation. However, at least two retrospective studies provide convincing arguments for its rationale.8,9 In the first study, of 40 patients undergoing noncardiac surgery less than six weeks after coronary stenting, seven (18%) had an MI, 11 (28%) had major bleeding and eight (20%) died.8 All deaths and MIs, and eight of the 11 bleeding episodes occurred in patients who had surgery less than two weeks after coronary stenting. In the second study, eight (4.0%) of 207 patients who had surgery within two months of coronary stenting suffered an MI, of whom six (2.9%) died.9 All deaths and MIs occurred among the 168 patients who had surgery within six weeks of stent placement. No major adverse event occurred in the 39 patients operated seven to nine weeks after stent placement. Those two studies did not determine whether the acute ischemic complications were due to coronary stenting or to the increased inflammatory and procoagulable state of those patients and the presence of other vulnerable plaques. In addition, they did not test whether postponing of surgery could improve outcome or not. However, they clearly indicate that noncardiac surgery within six weeks of coronary stenting is associated with an increased risk of serious peri-operative cardiac events.
It is difficult to argue against the authors second conclusion. To maintain their competence, anesthesiologists must continuously review guidelines related to perioperative care, particularly if they relate to coronary artery disease which largely contributes to perioperative morbidity and mortality. However, it is unclear how Patterson et al. reached their first conclusion. Did they interpret the most frequent anesthesiologists answers as the right approach? If that was the case, it would be wrong and maybe presumptuous for anesthesiologists alone to establish a policy on a highly specialized cardiology topic. To have any credibility, any perioperative policy on coronary stenting should involve experienced interventional cardiologists and expert perioperative physicians (e.g., anesthesiologists and intensivists). This is how the ACC/AHA guidelines were developed. It would probably be wiser for Canadian anesthesiology departments to refer to those guidelines or similar ones rather than develop their own.
It is possible that Patterson et al. intended to stimulate Canadian anesthesiology departments to develop a policy based on the existing ACC/AHA guidelines. This would make their first conclusion more acceptable, but not necessarily right for many reasons. First, there is a paucity of information and an absence of controlled studies on the perioperative outcomes of patients with recent coronary stenting. Second, the processes leading to stent thrombosis are complex and multifactorial. They involve the type of stent implanted, its total length, the size of the final lumen diameter and the possibility of persistent dissection at the time of procedure.6 The consideration of all those factors makes it almost impossible to establish guidelines applicable to all patients with coronary stents. Third, the current ACC/AHA perioperative guidelines regarding coronary stents apply only to patients with bare metal stents, not to brachytherapy (e.g., intra-coronary radiation with gamma or beta emitters) or drug-eluting stents.11 Finally, this highly specialized technology evolves rapidly and is constantly challenged by new reports. For example, the four to six weeks delay recommended by the ACC/AHA was recently questioned following a case of fatal MI due to stent thrombosis in a patient who underwent lung resection six weeks after the prophylactic implantation of a coronary stent.12 In their report, the authors strongly argued that complete stent re-endothelialization takes up to three months.13 Consequently, they recommended a waiting period of three months between stent implantation and elective surgery, as previously suggested by Chassot et al.14 This discrepancy between the waiting period recommended by Chassot et al. and the ACC/AHA guidelines is only one of the controversies that Canadian anesthesiology departments would face if they established their own policy.
The rapid development of new strategies to prevent in-stent restenosis is another argument against any policy setting a fixed delay between coronary stenting and elective surgery. In-stent restenosis is a phenomenon mainly due to neointimal proliferation. It peaks around the third month and reaches a plateau between the third and sixth month after the procedure. Brachytherapy has been used to treat in-stent restenosis and drug-eluting stents have been proven to prevent it.11 Brachytherapy inhibits the intimal hyperplasia by breaking the cells DNA and blocking mitosis. Covered with a polymer and a drug spread over the metal, drug-eluting stents provide the slow release of a substance inhibiting cell proliferation. Sirolimus (an antifungal with potent cell cycle inhibitory effect) and paclitaxel (a compound with potent anti-tumour activity) are the commonly used substances in drug-eluting stent therapy.11 A common effect of brachytherapy and drug-eluting stents is delayed re-endothelialization. Little is known on how brachytherapy or drug-eluting stents should be managed perioperatively. The management may differ considerably depending on the stent structure, its polymer coating and its active pharmacological agent. The clinical importance of delayed re-endothelialization by drug-eluting stents was recently highlighted in a patient who, 12 weeks prior to knee surgery, had simultaneous implantation of a bare metal stent in his right coronary artery (RCA) and two paclitaxel-eluting stents in his left circumflex artery (LCX).15 Two hours after the procedure, the patient developed acute MI. Coronary angiography revealed total occlusion of both drug-eluting stents in the LCX and normal flow in the RCA. Recanalization of the LCX was performed successfully and the patient did well. How long after the implantation of those drug-eluting stents should the patient have waited before that relatively minor surgery? This is another issue that cannot be resolved through a policy setting a fixed waiting period between coronary stenting and surgery.
In summary, the survey by Patterson et al. should alert all anesthesiologists about the risk of major adverse events in surgical patients with recent coronary stents. However, it would be hazardous for Canadian anesthesiology departments to establish on their own a fixed policy on the acceptable delay between coronary stenting and elective surgery. Such a policy could rapidly become obsolete with the risk of denying the appropriate surgery to a specific patient at the appropriate time. It seems wiser for anesthesiologists to adopt a case by case approach with the following precautions. First, in a surgical patient with a history of PCI and coronary stent, determine the date of the procedure, the kind of stent inserted and the possibility of complications during the procedure. Second, consider all patients with a recent stent implantation (e.g., less than three months for bare metal stents and less than one year for brachytherapy or drug-eluting stents) as high-risk and consult an interventional cardiologist. Third, any decision to postpone surgery, continue, modify or discontinue antiplatelet regimes must involve the cardiologist, the surgeon, the anesthesiologist and the intensivist who will balance the risk and benefit of each decision. Finally, if an emergency noncardiac surgery is necessary in a patient with recent coronary stenting, the surgery should preferably be performed in a centre with interventional cardiology care for prompt intervention in case of stent thrombosis. Those precautions are based on the currently available information. Anesthesiologists are encouraged to follow the new developments on coronary stents to provide the best possible care to patients presenting with this condition.
