Cold temperatures put stress on the cardiovascular system. They do this in 2 different ways.
- Cold temperatures increase blood pressure.
When the body temperature falls, the blood vessels under the skin get narrower. This shunts warm blood away from the surface of the body to reduce the amount of heat lost from the skin. The narrowing of blood vessels under the skin causes an increase in pressure in the blood vessels. This makes the heart work harder.
For people with cardiovascular disease, this causes an increase in blood pressure and puts additional load on the heart. It may cause symptoms of angina or shortness of breath.
- Cold temperatures cause coronary arteries to narrow.
When you breathe in cold air through your mouth, the nerve endings in the back of your throat are stimulated. This causes your coronary arteries to narrow. This is called "reflex vasoconstriction".
The narrowing of the coronary arteries because of the cold is known as a spasm of the coronary arteries and may result in angina.