Abstract
Patients with a coronary stent, particularly a drug-eluting stent, are treated for 6 to 12 months with dual antiplatelet therapy. Premature discontinuation of the GIIa/IIIb inhibitor can lead to increased risk of coronary stent thrombosis, particularly given the increased thrombotic tendency in the perioperative period. Therefore optimal timing of surgery and antiplatelet therapy management are critical in these patients, and a guideline from the ACC/AHA was published in 2016. Surgery can safely be performed at 6 months after stent placement and can be considered at 3 months after stent placement if the risk of delaying surgery is greater than the risk of stent thrombosis. Ideally, dual antiplatelet therapy should be continued for at least 6 months, and then aspirin can be continued. A robust discussion between the surgeon, anesthesiologists, and cardiologists is the optimal strategy but is not always possible.
Keywords
coronary stent, clopidogrel, dual antiplatelet therapy, aspirin, glycoprotein IIb/IIA inhibitors, thrombosis
Case Synopsis
A 65-year-old man is admitted for a colon resection for a nonobstructing cancer. He had a myocardial infarction 4 months ago with placement of a drug-eluting stent. He has been asymptomatic since the stent placement. The patient is currently taking clopidogrel and aspirin, as well as atenolol for his hypertension. Surgery is scheduled for 7 days from now.
The anesthetic management of a patient who presents with a drug-eluting stent is a major challenge for the anesthesiologist, the surgeon, and the cardiologist. Soon after the introduction of percutaneous coronary interventions with coronary stents, there began to appear in the literature a series of case reports of stent thrombosis. The key question for a patient with a prior coronary stent placement is the optimal timing of surgery and management of the antiplatelet agents. Specifically, should the agents be continued or held, given the risks of stent thrombosis versus the risks of increased bleeding in the perioperative period? Acute thrombosis of a coronary stent has been known to lead to myocardial infarction and potentially death.
Problem Analysis
When patients present for surgery who have had a prior drug-eluting stent placed, a key decision preoperatively is when the surgery should be performed (i.e., how long to delay after stent placement) and the management of antiplatelet therapy. In 2016 the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines published a “focused update” on the duration of dual antiplatelet therapy in patients with coronary artery disease. There are no randomized trials of the optimal perioperative strategy including bridging therapy and therefore the recommendations were based on both randomized trials from the nonoperative setting and cohort studies of surgical patients. A second factor is the changes in antiplatelet management based on the generation of drug-eluting stent. The newer stents need shorter therapy because of the lower thrombotic tendency. The key question is the balance of bleeding risk from surgery performed on dual antiplatelet therapy versus thrombotic risk and the development of a myocardial infarction given the time from stent placement and reendothelialization and the use of different antiplatelet agents. The interventional cardiologists may take the anatomy of the stent placement into the calculus to decide on optimal treatment.
Definition
In a patient with a history of coronary stent placement undergoing noncardiac surgery, it is critical to determine (1) the indication for the coronary stent, (2) the type of coronary stent (first or second generation), (3) current antiplatelet therapy, and (4) the urgency of surgery.
Recognition
Although the preoperative preparation of the patient with a coronary stent has been the primary focus, the intraoperative detection and treatment of a stent thrombosis is also critical. Intraoperative or postoperative coronary stent thrombosis presents similar to other myocardial infarctions in the perioperative period but may more likely manifest as ST-segment elevation as opposed to depression. The extent of myocardium at risk from a stent thrombosis may be extensive and therefore may manifest as hemodynamic changes and may result in heart failure.
Management
Evidence
Several reports suggest that drug-eluting stents may represent an additional risk over a prolonged period (up to 12 months) compared with those with coronary disease and no recent stent placement, particularly if the use of antiplatelet agents is discontinued. Schouten’s group retrospectively evaluated 192 patients who underwent noncardiac surgery after successful percutaneous coronary intervention (PCI) for unstable coronary artery disease within 2 years of the procedure. Drug-eluting stents accounted for 52% of the stents placed. Of the 192 patients, 30 underwent surgery before the recommended discontinuation of dual antiplatelet therapy for the particular stent (30 days for bare-metal stents and up to 6 months for sirolimus-eluting stents). In patients in whom antiplatelet therapy was stopped before the required time for use of clopidogrel (early-surgery group), the incidence of death or nonfatal myocardial infarction (MI) was 30.7% compared with 0% in patients who continued antiplatelet therapy. The elevated risk for stent thrombosis and cardiovascular events, however, seems to abate over time. In the Evaluation of Drug-Eluting Stents and Ischemic Events (EVENT) registry of 4637 consecutive patients, 4.4% underwent major noncardiac surgery in the ensuing year. They reported a relative 27-fold increased rate of cardiovascular events in the week following surgery versus any other week after stent implantation, but the absolute rate was only 1.9%. Wijeysundera and colleagues evaluated 8116 patients who underwent noncardiac surgery in Ontario, Canada, and found that 34% had a coronary stent implanted within the 2 years before surgery. Drug-eluting stents represented a third of the stents placed. Patients with bare-metal stents implanted less than 45 days before surgery had a 6.7% cardiovascular event rate, which dropped to 2.6% with a stent implanted 45 to 180 days before surgery. Subjects with a drug-eluting stent had a 20.2% cardiovascular event rate in the first 45 days after stent implantation, and the rate became similar to that in subjects without stenting when the stent was implanted more than 180 days before surgery. Bangalore and colleagues studied the impact of drug-eluting stents (DESs) compared with bare-metal stents (BMSs) placed preoperatively in 8415 patients in Massachusetts. In this cohort, the death, MI, and bleeding event rate was 8.6% in the first 30 days after PCI, dropping to 5.2% when surgery was performed more than 90 days after coronary revascularization. Using propensity matching to compare the BMS and DES populations, the death and MI rate was higher in the BMS cohort. In a Scotland-wide retrospective cohort analysis, perioperative death and ischemic cardiac events were much more common within the first 6 weeks after stent implantation than after 6 weeks, 42.4% versus 12.8%, respectively. Forty-five percent of the revascularizations in this cohort were performed for an acute coronary syndrome, increasing the baseline risk of the cohort. The event rate was higher in patients who underwent revascularization because of acute coronary syndromes within 6 weeks, in whom it reached 65%. In contrast to other reports, no temporal differences were noted between the BMS and DES groups. Data from more recent large observational studies suggest that the time frame of increased risk of stent thrombosis is on the order of 6 months, irrespective of stent type (BMS or DES). In a large cohort of patients from the Veterans Health Administration hospitals, the increased risk of surgery for the 6 months after stent placement was most pronounced in those patients in whom the indication for PCI was an MI. In nonsurgical patients with stable coronary artery disease or low-risk acute coronary syndromes treated with zotarolimus-eluting stents, 3 months of dual antiplatelet therapy demonstrated no difference in cardiac outcomes compared with 12 months of therapy. In contrast, dual antiplatelet therapy beyond 1 year after placement of a drug-eluting stent, compared with aspirin therapy alone, significantly reduced the risks of stent thrombosis and major adverse cardiovascular and cerebrovascular events but was associated with an increased risk of bleeding.
Guidelines for Perioperative Management
The recommendations as of 2016 are shown in Table 22.1 . Surgery can safely be performed at 6 months after stent placement and can be considered at 3 months after stent placement if the risk of delaying surgery is greater than the risk of stent thrombosis. Ideally, dual antiplatelet therapy should be continued for at least 6 months and then aspirin can be continued. Timing of noncardiac surgery is illustrated in Fig. 22.1 . A robust discussion among the surgeon, anesthesiologists, and cardiologists is the optimal strategy but is not always possible.
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