In-Hospital Acute MI: Despite Numerous Predictors, Solutions Remain Elusive

In-hospital acute MI is linked to various cardiovascular risk factors and markers of acute illness, and it portends extremely poor prognosis, according to a study of 1.3 million US veterans encompassing more than a decade’s worth of data.

At 1 year, the mortality rate was almost twice as high—nearly 60%—among patients who had experienced acute MI while hospitalized for reasons other than ischemic heart disease compared with matched controls, Steven M. Bradley, MD (Minneapolis Heart Institute, MN), and colleagues report in a paper published today in JAMA Network Open. After adjustment for potential confounders, in-hospital acute MI patients saw an even greater increase in 1-year mortality risk, with an odds ratio of 2.41 (95% CI 1.83-3.18) versus controls.

Earlier research has shown that in-hospital STEMI can result in delayed revascularization and worse short-term outcomes compared with out-of-hospital STEMI, they point out, adding, “Little is known about the full spectrum of hospital AMI.”

The new study “doesn’t as of yet inform care, but it provides a better understanding of how often patients who are hospitalized have myocardial infarction, what appear to be risk factors that put patients at high risk of MI, and what the long-term outcomes are,” Bradley told TCTMD.

Most of the knowledge about how to manage MI is based on patients whose events occur outside of the hospital setting, often at home, he noted. Focusing on in-hospital acute MI offers a different perspective.

“These sorts of descriptive studies that first raise the questions of ‘how big is the problem, how often is it happening, and what are the outcomes?’ [should encourage] others to think as a community about how we can address these next questions” regarding prevention and management, Bradley urged.

Mortality Nearly 60% at 1 Year

For their analysis, Bradley et al looked at 1.3 million admissions at US Veterans Health Administration facilities between July 2007 and September 2009. Within this population, 5,556 patients experienced in-hospital acute MI more than 24 hours after their admission, amounting to an incidence of 4.27 per 1,000 hospitalizations.

Numerous factors were independently associated with an increased risk of in-hospital acute MI. Predictors of lower risk included atrial fibrillation, history of anemia, depression, and low heart rate (< 60 beats/min).

Independent Predictors of In-Hospital Acute MI

Informed by a detailed review of medical records, the researchers compared 687 cases with an equal number of individually matched controls. Patients who had experienced in-hospital MI had higher mortality during their hospital stay (26.4% vs 4.2%) as well as at 30 days (33.0% vs 10.0%) and 1 year (59.2% vs 34.4%; P< 0.001 for all comparisons). STEMI patients were more likely to die than NSTEMI. All-cause readmission rates at 1 year, however, were similar between the case and control groups at 54.4% and 52.4%, respectively (P = 0.52).

“This study highlights the importance of in-hospital AMI as a common and high-risk clinical condition among hospitalized patients,” the investigators conclude.

Awareness of in-hospital cardiac arrest—with an event rate of 4 per 1,000 hospital admissions—is far greater and may be leading to improved survival for this group, they comment, observing that more than $300 million has been spent “nationally to equip, train, and accredit clinicians and hospitals in resuscitation care. . . . Similar emphasis on research to understand the modifiable risks of in-hospital AMI and optimal treatment are lacking, despite a similar prevalence and poor long-term survival outcome of in-hospital AMI.”

While some of these MIs may be caused by traditional culprits like plaque disruption and thrombus formation, the current findings point to the possibility that “physiological disturbances” in hemoglobin level, heart rate, white blood cell count, and serum urea nitrogen level could be contributing factors, Bradley and colleagues suggest.

Exactly what leads to the very high 1-year death rate is an “outstanding question,” Bradley told TCTMD. Better care might improve outcomes, but “it is notable that these patients do have a lot of comorbidities and other factors during their hospitalization that suggest they’re sick patients to begin with. It’s probably not just the myocardial infarction” that puts them at risk, he explained.

Given the diverse clinical factors leading to the acute MI, “it becomes a lot harder to create standardized processes for patients who may have other active conditions that have led to their initial hospitalization and have to be considered when managing these patients,” he commented.