Did guidelines affect post-stent surgical outcomes?

The American College of Cardiology and the American Heart Association released guidelines in 2007 advising physicians to delay surgery following a cardiac stent placement. But did they help reduce major adverse cardiac events (MACE) following these secondary surgeries? According to a study published Sept. 3 in JAMA: Surgery, the answer isn’t completely clear.

Researchers from the Veterans Administration medical system wanted to know if there had been an effect on their patients following the 2007 announcement. To that end, they gathered data from patients who underwent stent surgery followed by elective surgery from 2005 to 2010, to show rates before and following the guideline’s publication.

Laura A. Graham, MPH, of the Center for Surgical, Medical Acute Care Research and Transitions (C-SMART) at the Birmingham Veterans Affairs Medical Center in Alabama, and colleagues identified 8,034 patients from the pre-guideline period and 8,600 patients post-guideline. They compared length of time between stent implantation and elective surgery as well as whether there were major adverse events following elective surgery.

The research team found that the mean length of the period between stent and secondary, elective surgery did increase over time for patients who received a drug-eluting stent, from 323 days to 404 days, but decreased for patients who received a bare metal stent from 402 days to 309 days. Interestingly, these trends had already begun prior to the release of the guidelines.

While overall adverse events decreased from the start of the reviewed period through to 2010 by 0.9 percent, in a similar trend to the changes in length of delay between stent and surgery, over time the incidence of 30-day MACE decreased. Patients who received drug-eluting stents experience MACE rates which dropped from 5.5 percent in 2005 to 4.3 in 2006 and beyond. Major adverse cardiac events occurred at a rate of 4.3 percent for bare metal stents in 2005, increasing to 8 percent in 2007, before dropping down to 4.8 percent following the guideline’s publication.

In general, pre-guideline 30-day MACE occurred in 4.2 percent of cases prior to the guidelines and 3.3 percent following the release of the guidelines in 2007. A significant change was seen between the MACE rates if the subsequent surgery occurred one or two years following the cardiac stent implant, dropping from 4.8 percent to 2.6 percent between one year post and two years post stent.

Graham et al suggested a few possibilities as to why seemingly anticipatory trends occurred. They wrote that the trends the research team noted may have been due to physicians already having some knowledge of the research behind the guidelines or foreknowledge that the guidelines were coming.

In keeping with the shorter length of recovery time between stent and surgery suggested by the guidelines, one finding appeared to point to the use of bare metal stents more frequently in certain subsets of patients on a lesser health trajectory. Graham et al postulated that physicians, knowing that these patients were going to need further surgery went with bare metal stents to accommodate that need; however there was not enough data to confirm.

These trends, Graham et al wrote, may also have been impacted by other factors that would require more scrutiny. Consequently, the authors suggested further research into what these other factors may have been that impacted physician decisions and patient outcomes.