Study Hints That Many ICU Admissions for Acute MI Patients May Be Unnecessary

Whether patients with acute MI are admitted into intensive care units (ICUs) varies widely across US centers, according to a study published online September 11, 2015, ahead of print in the American Heart Journal. Hospital-level ICU use does not appear to influence risks of in-hospital mortality, but it is associated with greater use of critical care therapies. 

Take Home: Study Hints That Many ICU Admissions for Acute MI Patients May Be Unnecessary

“These findings suggest uncertainty about the appropriate use of this resource-intensive setting and a need to optimize ICU triage for patients who will truly benefit,” Harlan M. Krumholz, MD, SM, of Yale-New Haven Hospital (New Haven, CT), and colleagues write. 

The researchers retrospectively looked at data on 114,136 acute MI hospitalizations between 2009 and 2010 at 307 hospitals participating in the Premier hospital discharge database. Hospitals were divided into quartiles according to their proportion of acute MI patients who were directly admitted to the ICU—defined as having a room and board charge for a medical, coronary, surgical, or general ICU bed during the first day in the hospital.

The median proportion of patients admitted to the ICU was 48%, although that figure ranged from 0% to 98% across individual centers and from 20% to 71% across quartiles. Median ICU admission was highest for patients with STEMI (75%), followed by those who received or did not receive revascularization (67% and 38%, respectively), and NSTEMI patients (35%). Within each of those patient groups, however, there was substantial across-center variation.

Disconnect Between ICU Use and Outcomes  

In the overall acute MI cohort, risk-standardized in-hospital mortality rates were nearly identical across the 4 quartiles of ICU use: 6.0%, 6.0%, 6.1%, and 5.9% from lowest to highest (P = .73). The same held true for the subgroup of patients who were not admitted to the ICU.

In the subgroup of patients who were admitted to the ICU, however, the risk-standardized mortality rate was lowest among the hospitals with the greatest ICU use (6.5%) and increased across quartiles of declining ICU use (7.1%, 7.9%, and 8.7%, respectively; P < .01).

In general, the proportion of patients receiving particular therapies increased as ICU use grew, from the lowest to highest quartiles (P < .05 for all). These included:

  • Mechanical ventilation, excluding noninvasive positive pressure ventilation: 13% to 16% 
  • IV vasopressors and/or inotropes: 17% to 21%
  • Intra-aortic balloon pumps: 4% to 7%
  • Pulmonary artery catheters: 4% to 5%
  • Any of the 4 therapies: 21% to 26%

Those trends were reversed in the subgroup of patients admitted to the ICU, with fewer therapies used at a hospital level at centers with greater ICU use.

“Together with the similar mortality rates seen in the overall group of patients with [acute MI] and the non-ICU subgroup of patients with [acute MI], these results suggest that at the margin, hospitals admitting a larger proportion of patients to the ICU may be admitting a group of patients with weaker indications for critical care therapies,” the authors say.

Refinement Needed in the Contemporary Era

Before the introduction of ICUs, early death and complications were common among acute MI patients. Adoption of the units improved outcomes, but “given the marked evolution in the clinical care and evidence base for [acute MI], the value of ICUs for many of these patients in contemporary practice warrants closer scrutiny,” Dr. Krumholz and colleagues write.

“Although critical care may be a lifesaving intervention for appropriate patients, it may not be providing value for all patients,” they add. “The decision to use an ICU is important not only because it is resource intensive, but also because ICUs potentially pose inherent risks for patients. Our findings suggest that we may not be optimally utilizing these highly specialized resources.”

The wide variation in ICU use seen across subgroups of acute MI patients suggests that differences are due to hospital-level and not patient-level factors, the authors say, including “consideration of bed availability, patients’ wishes, physician incentives, and differing beliefs about best practices.”  

The study “suggests an opportunity where improving triage could enhance resource utilization without undermining outcomes,” they write, pointing to the possibility of efforts targeting both physicians and hospitals.

“At the provider level, a renewed emphasis may need to be placed on the use of appropriate risk stratification for [acute MI] patients at presentation,” the researchers advise. Another opportunity exists at the hospital level, they add, noting that “for many patients admitted to ICUs for monitoring and prevention of complications, an intermediate-care strategy such as step-down units or general telemetry units may provide an equally safe yet more cost-effective alternative.”

Finally, the authors say, future studies should focus on identifying the causes of variation in ICU use, the patients who are most likely to benefit, and the point at which any value from ICU treatment disappears.

Chen R, Strait KM, Dharmarajan K, et al. Hospital variation in admission to intensive care units for patients with acute myocardial infarction. Am Heart J. 2015;Epub ahead of print.


  • The study was funded by grants from the National Center for Advancing Translational Sciences, the National Heart, Lung, and Blood Institute, and the Patrick and Catherine Weldon Donaghue Medical Research Foundation.
  • Dr. Krumholz reports receiving research agreements with Johnson & Johnson and Medtronic through Yale University to develop methods of clinical trial data sharing and serving as chair of a cardiac scientific advisory board for UnitedHealth.

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