ABSTRACT & COMMENTARY
By Jeffrey Zimmet, MD, PhD
SOURCE: Holcomb CN, et al. The incremental risk of noncardiac surgery on adverse cardiac events following coronary stenting. J Am Coll Cardiol 2014;64:2730-2739.
Contemporary data suggest that approximately one in five patients will require non-cardiac surgery within 2 years of coronary stent implantation. The most feared complication here is stent thrombosis, which is more common in this setting due to the combination of stopping antiplatelet drugs and the systemic pro-thrombotic and pro-inflammatory effects of the surgery itself. While stent thrombosis is virtually always a serious event, it is especially morbid in the postoperative setting due to the need for antithrombotic medications and the consequent risk of bleeding at the surgical site. As an academic interventional cardiologist, I find that a significant proportion of my clinic consultations center around this topic: How soon can my stented patient undergo surgery? Can the antiplatelet agents be held for surgery? What is the risk of adverse cardiac outcomes if my patient with stents goes to surgery now?
One of the major issues with studying this question involves identifying large enough patient numbers to come to firm conclusions. Holcomb and colleagues mined the Veterans Affairs database to identify all patients receiving bare metal stents (BMS) or drug-eluting stents (DES) between October 1, 1999 and September 30, 2009. They then compared all patients who had noncardiac surgery within 24 months of coronary stent implantation to those with stents who did not undergo subsequent surgery. Each patient undergoing surgery was matched to two patients who did not have surgery. Importantly, the authors tracked events by time from stenting in both the surgical and nonsurgical cohorts, as cardiac events in post-stent patients are most frequent in the early weeks to months. The incremental risk of cardiac events following noncardiac surgery was then expressed as a risk difference.
As would be expected, the incremental risk was highest in the early weeks post stenting, and fell off with time. The risk difference for adverse cardiac events with noncardiac surgery, adjusted for surgical characteristics, was 2.8% during the first 6 weeks, 2.0% between 6 weeks and 6 months, and then decreased to just under 1% after 6 months, where it remained stable out to 24 months. These differences were driven primarily by disparities in death and MI. When surgery was performed more than 6 months after stenting, the incremental risk of surgery was decreased significantly, primarily for patients having more complex inpatient procedures and for patients who were defined as high risk by the revised cardiac risk index. Minor outpatient procedures were not associated with a significant incremental risk. Therefore, the authors suggest that waiting until at least 6 months post stent is important, primarily for higher-risk patients and procedures.
When looking at patients by stent type, the study found that event rates were higher in bare metal stent (BMS) patients whether or not they underwent surgery. Within the first 6 months post-stent, the incremental risk of surgery was similar regardless of stent type. The incremental risk dropped significantly after 6 months only in patients with DES, but not in those with BMS.
This study addresses multiple important issues in the care of this common and challenging set of patients. Firstly, it supports the notion that the initial 6 weeks post-stent is the highest-risk time period during which nearly 10% of patients in this study experienced an adverse cardiac event. Surgery should be avoided during this period if at all possible. Conversely, patients with a recognized need for noncardiac surgery within 6 weeks should avoid coronary stenting, with consideration given to CABG when appropriate, to balloon angioplasty alone when feasible, or to medical therapy without revascularization. Patients with stents who must go to surgery within 6 weeks should continue dual antiplatelet therapy if possible, although there are no data to suggest that this improves safety.
The incremental risk of surgery remains elevated between 6 weeks and 6 months, but then appears to plateau and remains relatively stable out to 2 years and most likely longer. Although current ACC/AHA guidelines recommend delaying surgery for at least 12 months after DES implantation, this study would suggest that a time cutoff of 6 months would provide similar outcomes. This is in line with several other recent studies, and is in agreement with the shorter 6-month duration currently recommended by the European Society of Cardiology. But while the peri-operative risk drops after 6 months, it levels off and remains significant even at 24 months. For all patients with prior coronary stents, serious consideration should be given to continuing aspirin peri-operatively regardless of time since implantation, and to performing complex and higher-risk surgeries at centers with full cardiac interventional capabilities.
Although it appears counterintuitive, the observation that patients with BMS have higher post-surgical event rates than those with DES is clearly demonstrated here. The evidence supports the idea that this increased risk is more likely due to the patient comorbidities that led to the preference for BMS, rather than to an interaction with stent type and surgery. It also calls into question the strategy of implanting BMS in patients requiring early surgery. More studies will be required to define the optimal solution for such patients.