References
http://www.webmd.com/heart-disease/ss/slideshow-visual-guide-to-heart-disease (signs and symptoms of a heart attack)
http://www.fitness.gov/
Coghlan, Andy. "Laughing all the way to a healthier heart." New Scientist 185.2490 (2005): 14. Academic OneFile. Web. 22 Feb. 2014.