Winter poses risks for those susceptible to heart disease. Three factors can combine to make it a dangerous time, specialists at the University of Pittsburgh School of Medicine suggest.

First, cold weather causes arteries to constrict, which reduces their ability to move blood and magnifies the significance of any blockages.

Second, winter is the time for shoveling snow. From complete rest, the body and heart must move to maximum exertion, usually in an irregular way as the shoveler alternates heaving snow and pausing to catch breath. It's no way to treat a weak heart.

Finally, many people feeling the symptoms of heart disease postpone taking them seriously until after the holidays are over. That just increases the risk of a heart attack.