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Sudden temperature swings may trigger MI

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Hitinder S. Gurm

ORLANDO, Fla. — Large day-to-day changes in temperature may increase risk for MI, leading researchers for a new study to suggest that extreme weather events and global warming may influence MI.

“It is well-known that environmental stress can trigger MIs,” Hitinder S. Gurm, MD, associate chief clinical officer of the cardiovascular/neuro subsegment at the University of Michigan, said during a web briefing before the American College of Cardiology Scientific Session. “Our study was focused on how changes in temperature impact MI risk.”

Gurm and colleagues evaluated data from the Blue Cross Blue Shield of Michigan Cardiovascular Consortium (BMC2)-PCI — a multicenter, quality improvement registry that tracks in-hospital outcomes of every patient who undergoes angioplasty or receives a stent at Michigan hospitals. In total, 30,404 patients with STEMI who underwent PCI at 45 hospitals were included in the analysis. Data on daily temperatures were downloaded from the Weather Underground website for each hospital ZIP code, and temperature fluctuation was defined as the difference between the highest and lowest temperature recorded on the day of presentation.

Results showed temperature fluctuations from 0°C to 5°C on 16.37% of days, 5°C to 10°C on 41.97% of days, 10°C to 15°C on 32.4% of days and more than 15°C on 9.26% of days.

As temperature fluctuation increased, Gurm said, the risk for MI also increased. For every 5°C increase in temperature fluctuation, risk for MI increased about 5%. Fluctuations of more than 25°C were also linked to greater increases in MI, as compared with smaller temperature fluctuations of 10°C to 25°C.

The researchers also assessed the effect of baseline temperature on the association between temperature fluctuation and risk for MI. Data demonstrated a strong, statistically significant interaction between the day’s average temperature and the effect of the temperature change on MI risk. On warmer days, the effect appeared to be more pronounced, according to Gurm.

“As the temperature rises, the effect that we see increases, so that around an average temperature of 30°C, we see a marked change in the likelihood of having more MIs with a change in daily temperatures,” Gurm said.

At the far end of the spectrum, for instance, a temperature fluctuation of 35°C to 40°C on a hot summer day could result in an almost doubling in the risk for MI than on days with no fluctuation.

One reason for this difference may be that people tend to stay indoors on cold days and, therefore, are not exposed to outdoor temperatures, according to Gurm.

“This is important because temperature is something everyone is exposed to. If we look at current temperatures, we have cold days and warm days and are used to what happens. With global warming, we expect to see warmer nights and actually a decrease in the diurnal variation. Paradoxically, this may lead to a reduction in heart attacks,” Gurm said while discussing the study’s implications. “In addition to that, though, we might find increased extreme weather events, which may have increased temperature swings that will lead to an increased risk for heart attacks.”

Although beyond the scope of the study, he noted that where a person lives may affect which of these factors may be more dominant, and physicians may see both a decrease and an increase in risk for attacks with global warming.

“Global warming, with its opposing effects, might impact how the population experiences MI,” Gurm said. “On another note, we can pretty much predict the temperature for a given day. In the short term, this might allow us to study why people have heart attacks on days with greater temperature fluctuation and may allow us to come up with strategies that may help us to negate that effect.” – by Melissa Foster

Reference:

Andersson HB, et al. Abstract 1155-267. Presented at: American College of Cardiology Scientific Session; March 10-12, 2018; Orlando, Fla.

Disclosures : The BMC2-PCI registry is funded by Blue Cross Blue Shield of Michigan. Gurm reports he receives consultant fees/honoraria from Osprey Medical.