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Usual MI pattern may shift after disaster, study finds

Thursday March 7, 2013
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The upheaval caused by Hurricane Katrina seems to have disrupted the usual timing of myocardial infarction in the New Orleans area, shifting peak frequency from weekday mornings to weekend nights, according to a study. The change in pattern persisted a full five years after the storm.

The study, which researchers said could inform decisions about hospital staffing after natural disasters, compared the timing of MI in patients admitted to Tulane Medical Center six years before and five years after the storm hit the Gulf Coast in August 2005, devastating New Orleans with floods and killing more than 1,800 people.

The latest analysis, scheduled to be presented at the American College of Cardiology’s 62nd annual Scientific Session, expands on previously published research that looked at these trends during the three years post-Katrina. The new data show that even five years after the hurricane, MI was still less likely to occur in the mornings or on weekdays and instead was more frequent at night and on the weekends. That pattern is a major shift from what cardiologists and hospitals normally see.

The researchers pointed to prolonged periods of stress as the most likely cause. "The stress and devastation brought on by Katrina doesn’t just make a heart attack more likely, but it also can alter when they occur," Matthew Peters, MD, the study’s lead author and a second-year internal medicine resident at Tulane University School of Medicine, said in a news release. "It may even outweigh or augment some of the psychological mechanisms" behind MI.

MI tends to be more common in the morning and on weekdays, especially Mondays, because of surges in cortisol and catecholamines, higher-than-normal blood pressure and heart rate, and a dip in the body’s ability to break up blood clots. The shifts in behaviors and routines seen after the storm may have trumped some of these factors, Peters said.

Still, researchers found a potentially encouraging sign from this latest analysis: a slight return of Monday-morning MI in a pattern closer to pre-storm events. Before the hurricane, 23% of MI occurred on Mondays. The rate dropped to 10% in the three years after the storm and only recently crept up to 16.5%, although the change is not statistically significant.

"It suggests some normalization in employment and work patterns, but generally things still appear to be pretty much in disarray," Peters said.

He speculates that with so many people forced out of work after Katrina, weekday mornings and Mondays, in particular, became less stressful. In the last two years, the unemployment rate in New Orleans has dropped from 17.9% to 15.2%, but still is more than twice the pre-storm unemployment rate of 7%. Night and weekend MI may be more likely because day-to-day life at home became more anxiety-ridden with temporary housing, rebuilding homes and financial stressors, the researchers said.

Researchers looked at trends in a total of 1,044 confirmed MI cases: 299 before Katrina, 408 in the three years after Katrina and another 337 spanning four and five years after the storm.

Compared to the pre-Katrina group, morning and weekday MI continued to be a significantly smaller portion of total MI in the fourth and fifth years after the storm. MI occurring over the weekend was nearly twice as likely as before the storm hit (30.6% vs. 16.1% of all MI), and night MI remained significantly elevated as well (43.6% vs. 29.8%). Compared to the period spanning one to three years after the storm, years four and five showed non-significant decreases in morning, weekday and weekend MI and a substantial (but still not statistically significant) reduction in MI at night.

Patients in the post-Katrina group were more likely to be smokers (52.3% vs. 34.4%) and lack health insurance (17.1% vs. 8.4%) compared to those before the storm. No significant differences were noted between groups in terms of age, sex, ethnicity, comorbidities, medications or substance abuse. Excluded from the study were non-New Orleans residents, hospital transfers, patients with symptom onset while hospitalized and patients without adequate documentation of timing of symptom onset.

Peters said the research may affect hospitals and healthcare workers in areas hard-hit by hurricanes and other natural disasters. Acute-care settings tend to be understaffed at night or on the weekends because, under normal circumstances, fewer patients arrive. However, based on these findings, the opposite might be true for several years after a disaster. The MI pattern could affect patient outcomes as well because patients who are treated at night generally have higher failure rates for angioplasty, longer door-to-balloon times and higher rates of in-hospital mortality, Peters added.

"With the increased incidence of major disasters in the U.S. and worldwide, it is important to understand how these disasters affect the heart, because clearly they do," Peters said.

The study is scheduled for presentation March 9 at the ACC meeting in San Francisco.


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