October 08, 2013

Study could lead to revisiting non-cardiac surgery stent guidelines
Drug-eluting stents pose no greater risk of major heart attack following non-cardiac surgery than bare metal stents.

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In a finding contrary to current treatment guidelines, patients with drug-eluting coronary stents face no greater risk of heart attack than those with bare-metal stents if they have a non-cardiac surgery, according to a study by researchers at the University of Alabama at Birmingham published today in the Journal of the American Medical Association

mary hawn 02Current American College of Cardiology guidelines recommend delaying non-cardiac surgery in patients after coronary stent procedures for one year after implanting a drug-eluting stent (DES) and for six weeks after implanting a bare-metal stent (BMS). Undergoing a second surgery after having a stent implanted has been linked by past studies to the formation of blood clots around a stent, with the potential to block the coronary artery and cause a heart attack. 

The delays set down in the current guidelines were meant to reduce that risk. The rationale for why patients should wait a year after DES implant, versus just six weeks with a BMS, is that the risk of heart attack has been greater.

The UAB study showed, however, that major adverse cardiac events were associated with whether a patient had recent, emergency surgery or advanced cardiac disease (e.g., heart failure), not with stent type or timing of surgery. The study focused on patients undergoing non-cardiac surgery within two years of coronary stent placement.

“Our results suggest that we need to reevaluate the current guideline emphasis on stent type and surgical time for both DES and BMS,” said Mary T. Hawn, M.D., professor of surgery at UAB director of UAB’s program in gastrointestinal surgery and staff surgeon at the Birmingham Veterans Affairs Hospital. “Stent type was not associated with adverse events, and the risk of surgery after three to six months following stent placement returns to baseline. The data supports the design of future studies to determine safe timing of surgery following coronary stenting, as well as optimal medical management in these patient populations.”

The observational study investigated a large national sample of nearly 45,000 operations performed within 24 months of a coronary stent. UAB’s research team was able to assess detailed clinical and surgical factors associated with risk and determine which factors are most associated with the likelihood of having an adverse cardiac event.

“If the patient is having emergency surgery, that would definitely be more likely to be associated with an adverse outcome,” Hawn said. “If they had a recent myocardial infraction within six months prior to surgery, those patients were at a much more elevated risk than patients who had a coronary stent but didn’t have a myocardial infraction.”

Approximately 600,000 interventions using stents are performed annually, and up to 20 percent of patients will undergo at least one surgical procedure in the ensuing 24 months. Drug-eluting stents are preferred by cardiologists, as they have longer patency rates, but they also require longer treatment with anti-platelet medications. It is these anti-platelet medications that can also increase the risk of surgery.

“This is a daily clinical scenario that is confronting surgeons, anesthesiologists and cardiologists on how to best manage these patients safely,” Hawn said. “There is this tension of do we have to delay their surgery; how urgent is their surgery versus what is the risk of an adverse cardiac event?”

Hawn said previous data supporting delay for surgery following the use of a DES is limited and conflicting. Because this study provides better estimates of the risk in a large national cohort of patients with coronary stents, she believes the guidelines need to be re-evaluated.

“The main findings of our study suggest that it’s likely safe to operate on patients who have a DES sooner,” Hawn said. “And because of that, the guidelines probably should be revisited.”
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