Mortality Lower When STEMI Patients Sent to the ICU, but Why?

A new analysis of Medicare data raises additional questions about which patients with STEMI require management within an intensive care unit (ICU), a practice currently used for most such patients in the United States.

After zeroing in on a population of STEMI patients who could reasonably be managed in either an ICU or a non-ICU setting, researchers led by Thomas Valley, MD (University of Michigan, Ann Arbor), showed that admission to an ICU was associated with a lower 30-day mortality rate compared with admission to another part of the hospital (14.9% vs 21.0%; P = 0.04).

Valley noted to TCTMD that much work has been dedicated to understanding the best ways to open up arteries quickly for patients with STEMI, but less attention given to where patients should go in the hospital after that. About three-quarters of US patients with STEMI end up in the ICU—with variation across centers—but recent research has suggested this level of care may be overused, he added.

The current study, published online June 4, 2019, ahead of print in BMJ, “doesn’t necessarily disagree with that,” Valley said. But he indicated that it adds nuance to the discussion “by saying that there might be patients that are vulnerable and may be harmed if we just consistently take those patients out of the ICU and that in particular we need to better understand which patients benefit from the ICU and which ones don’t.”

Jason Neil Katz, MD (University of North Carolina School of Medicine, Chapel Hill), agreed with that assessment and credited the investigators with providing some insights into the uncertainties surrounding this important issue.

The study “sends many providers back to the drawing board. [They] have to ask themselves whether STEMI patients derive a benefit, whether it’s worth admitting patients to an ICU with marginal indications in the setting of STEMI given the challenges, particularly from a cost standpoint, of leveraging ICU care,” Katz commented to TCTMD.

Ultimately what is needed to provide clarity around who should go to the ICU are prospective, randomized studies, he said.

“It’s not until we get together and decide to tackle these controversial subjects in a prospective fashion that we’re really going to be able to come up with meaningful answers that are going to change care practices,” Katz said, adding that “we owe it to our communities to try to understand this better.”

Focusing on the Borderline

Most STEMI patients in the United States are admitted to an intensive or coronary care unit, and the associated costs are “enormous,” according to the authors. However, the uncertainty about whether it’s necessary is reflected both in variations in practice and differences in guidelines. The European Society of Cardiology recommends sending all STEMI patients to an ICU, whereas the most recent update to the US STEMI guidelines does not contain any specific advice to guide clinicians.

Valley et al explored whether ICU admission has an impact on STEMI outcomes by using Medicare claims data on 109,375 fee-for-service beneficiaries 65 or older who were admitted with a STEMI to one of 1,727 acute care hospitals between January 2014 and October 2015. Overall, 68.8% of patients were admitted to an ICU (which included coronary care units) and the rest were admitted to a non-ICU unit (which included general/telemetry wards or intermediate care).

The unadjusted 30-day mortality rate was higher in those admitted to an ICU (18.2% vs 13.8%), a difference that was mostly mitigated after accounting for patient and hospital characteristics in a multivariable regression analysis (17.0% vs 16.5%).

Going further, however, the researchers used an instrumental variable analysis to account for the differential likelihood of being admitted to an ICU based on distance from centers that had high ICU usage in the setting of STEMI. In that way, Valley et al identified a subset of patients—about 10% of the overall cohort—who were admitted to an ICU or non-ICU based only on how close they lived to a certain hospital. In this group, which was considered to have borderline or marginal ICU needs, ICU admission was associated with an absolute 6.1% lower risk of 30-day mortality compared with non-ICU admission.

Who Benefits?

Valley emphasized that the results apply only to those patients in whom admission to an ICU or non-ICU depended on where they lived, noting that some patients have clear indications for or against an ICU stay.

The study additionally forms a foundation upon which further studies looking into which STEMI patients within this borderline or marginal group benefit from ICU admission can be built.

Though this study gives a population-level view of who might have the most to gain from ICU admission—borderline patients were more likely to be over age 85 and to be free from organ failures—there’s still no way to pick out individual patients from within these groups who should receive more intensive care.

“A clear next step is for us to be able to identify their characteristics so that we can tell doctors: this is the type of patient who might benefit from going to the ICU,” Valley said.

Beyond that, researchers should seek to confirm whether ICU care has a benefit in these types of STEMI patients and identify what aspects of ICU care are most important, which would potentially allow clinicians to apply those features to non-ICU settings, he said.

Indeed, for Katz, the study highlights the need for additional research—particularly prospective and randomized—to sort this out.

“The value of those intensive care units, the cost-effectiveness of those intensive care units, really hinges on admitting the right patients that are going to derive some type of benefit from intensive care therapy over and above what they would have received in a non-ICU setting,” he said.