(RxWiki News) Heart disease patients may have an added reason to skip even simple activities such as shoveling snow on chilly days. They appear to be at an added risk of suffering coronary events when the air is cold.
Penn State researchers say that's because in individuals with heart disease, their bodies may be unable to compensate for the higher demand for oxygen when inhaling cold air.
"Discuss winter exercise with your cardiologist."
Lawrence I. Sinoway, Distinguished Professor of Medicine and director of the Heart and Vascular Institute at Penn State College of Medicine, noted that when individuals are doing some type of isometric activities -- strength training in a static position such as weight training or even carrying a briefcase -- and breathing cold air, the heart is doing more work and consuming more oxygen.
It's known that breathing in cold air during exercise may cause the oxygen to be unevenly distributed throughout the heart. In healthy individuals, the body will make changes and redistribute blood flow. In those with heart problems such as coronary artery disease, their bodies may be unable to make such adjustments in cold temperatures.
This may in part explain a peak in cardiac arrest deaths during the winter months.
"There are two different things going on here -- demand and supply," said Matthew D. Muller, a postdoctoral fellow at the Heart and Vascular Institute at Penn State College of Medicine.
"We thought that oxygen demand in the heart would be higher with cold-air breathing and we also thought that oxygen supply would be a little bit impaired. And that's generally what we found."
During the study researchers studied two groups of patients -- one healthy young adults in their 20s and the other healthy adults in their 60s in order to learn how the heart functions in patients without heart disease. The participants performed an isometric or static handgrip known to increase blood pressure. While they held down the grip for two minutes, investigators measured their heart and lung functions.
They found that there was a supply and demand mismatch in the heart's left ventricle, where oxygenated blood is received, but that the heart was still able to function appropriately. The findings suggest that healthy people can redistribute blood to the blood vessels entering the heart when faced with exercise while inhaling cold air.
The study was published both in the Journal of Applied Physiology and the American Journal of Physiology, Heart and Circulatory Physiology.