In-Hospital MI Linked to High Mortality Risk

Nancy A. Melville

January 29, 2019

The occurrence of acute myocardial infarction (MI) during hospitalization for other medical conditions is not uncommon and is linked to a significantly increased risk for poor outcomes, with 1-year mortality rates as high as 60%, new research suggests.

"Although significant work remains to determine the extent to which in-hospital AMI outcomes can be modified by addressing cardiovascular risk and concurrent illness, these findings should prompt clinicians to recognize patients with in-hospital AMI as having a high mortality risk," write the authors of the study, published online January 18 in JAMA Network Open.

Acute MI that occurs outside the hospital has been extensively studied, and those findings have improved treatment and led to substantial reductions in incidence and mortality, they note. Similar insights on patients who suffer acute MI when already in the hospital for other conditions are lacking.

For this analysis, Steven M. Bradley, MD, MPH, Minneapolis Heart Institute, and colleagues evaluated data from the US Veterans Health Administration between July 2007 and September 2009, and found that among the 1.3 million admissions, 5556 patients experienced in-hospital acute MI — an incidence of 4.27 in-hospital acute MI events per 1000 admissions.

In a matched cohort analysis, 687 patients who experienced acute MI (mean age, 73.3 years) were compared with an equal number of patients who did not (mean age, 73.4). In the acute MI group, 587 (85.4%) had ICD-9 codes indicating non-ST-segment elevation myocardial infarction (NSTEMI) and 100 (14.6%) had codes indicating STEMI.

Rates of in-hospital mortality were significantly higher in the acute MI group than in the non-MI group (26.4% vs 4.2%; P < .001), as were 30-day mortality rates (33.0% vs 10.0%; P < .001) and 1-year mortality rates (59.2% vs 34.4%; P < .001).

"Certainly, the 1-year mortality speaks to the very high risk associated with in-hospital MI, likely as a function of both the MI event and concurrent comorbidities," Bradley told Medscape Medical News.

The mortality rates are also significantly higher than previously reported rates for people with acute MI beginning outside the hospital — approximately 13% at 30 days and 25% at 1 year.

In the current study, key factors shown to be independently associated with in-hospital MI include being in the intensive care unit, having a history of coronary artery disease, and having markers of physiologic stress, such as an elevated heart rate (>100 beats/min; P < .001), a low hemoglobin level <8 g/dL; P < .001), and a high white blood cell count (≥14,000/μL; P < .001).

Other significant risk factors include a history of atherosclerotic disease, previous MI, and the presence of peripheral vascular disease.

"Decades of research have helped to clarify the risk factors associated with atherosclerosis and acute MI onset out of the hospital," the authors write. "The present study suggests a history of atherosclerosis and risk factors for atherosclerosis contribute to the risk of in-hospital acute MI, potentially reflecting a common pathway of spontaneous coronary plaque disruption and intraluminal thrombus formation (i.e., type 1 MI by universal classification schema) for some in-hospital acute MI."

The study adds to previous research by taking a broader look at various MI outcomes, Bradley noted.

"Previous studies have largely focused on STEMI and have compared in-hospital MI with MI that occurred outside the hospital," he said. "This study looks at the larger picture of in-hospital MI (STEMI and non-STEMI)."

"Further, by using matched controls, the study provides new insights into risk factors and outcomes of in-hospital MI."

The findings underscore the fact that "in-hospital MI is a high-risk finding that warrants careful clinical attention," Bradley noted.

Mortality Rates Higher Than Expected

Commenting on the study, Richard C. Becker, MD, Stonehill Endowed Chair and professor of medicine, University of Cincinnati College of Medicine, said the mortality rates are unexpectedly high.

"It might appear that these patients are already somewhat more prone to MI, but the mortality rates really suggest that there must be something more going on here because this is higher than what we would expect from individuals with this kind of risk profile," he told Medscape Medical News.

"This is clearly a unique group of individuals with very poor outcomes," he added, noting that not a lot of research has been dedicated this group over the years.

Although hospitals typically have carefully crafted algorithms to identify and treat patients who arrive having had an MI outside the hospital, the findings raise the issue of how well patients are managed when the event occurs in-house, he said.

"I think the impact of this study is that it poses the question of whether we are approaching patients who have a heart attack in the hospital with the same level of best-practice evidence, or is this an unmet need that requires our attention."

Ultimately, the study raises the question of why the mortality rates are so high, Becker noted.

"Was it because they had recurring heart attacks or heart failure or arrhythmia?" he asked. "We don't have a lot of that detailed information and, looking ahead, we therefore need to develop carefully constructed trials to understand these patients better and identify what the best practices are for this group of individuals."

The study was supported by the Veterans Administration Clinical Studies Research and Development Program. Bradley is associate editor of JAMA Network Open. Becker had no disclosures to report.

JAMA Network Open. Published January 18, 2019. Abstract

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