Jul 11, 2005 - 3:32 am EST

A rapid drop in air pressure - as opposed to cold weather - may trigger some Heart attacks, research shows. According to a study published this month, the incidence of Heart attack, but not Stroke, is increased in the 24 hours after a rapid fall in barometric pressure.

“Previous reports have shown that there are more (Heart attacks) in the wintertime,” said lead author Dr. Philip D. Houck, from The Scott & White Hospital and Clinic in Temple, Texas. But, this does not seem to relate to cold temperatures because even warm locations, such as Hawaii, have shown an increase in heart attacks during the winter, he explained.

Houck and others correlated atmospheric pressure data with the occurrence of heart attack and stroke in central Texas between 1993 and 1996. A total of 1327 heart attack patients and 839 stroke patients were identified.

The fall and winter showed the greatest variability in atmospheric pressure readings, the report indicates. As noted, an increased risk of heart attack, but not stroke, was seen in the day following a drop in air pressure.

“My experience taking care of patients over the years told me that the day after a major weather event, like a thunderstorm, we would see a cluster of heart attacks,” Houck said. “Our study now shows that a relationship does exist. The more the pressure falls, the greater the chance someone has of having a heart attack the next day.”

Changes in atmospheric pressure don’t explain all Heart attacks, the researchers say, and the risk is likely highest in individuals with Heart disease.

“An atherosclerotic plaque may be a lot like a bathysphere,” Houck said. As a bathysphere descends in the water, pressure accumulates. When they fail, however, it typically occurs during ascent when pressure drops. In a similar way, changes in barometric pressure may cause plaque rupture, resulting in an MI (Heart attack).”

SOURCE: American Journal of Cardiology July 1, 2005.