IMAGES PROVIDED BY:
1) SPL / Photo Researchers, Inc.
2) James Cavallini / Photo Researchers, Inc.
3) 3D Clinic
4) Stephen Smith / Riser
5) Nikolaevich / Photonica
6) Brand X Pictures
7) 3D4Medical
8) David Gifford / Photo Researchers, Inc.
9) PDSN / Phototake -- All rights reserved.
10) ERproductions Ltd
11) Medicimage
12) Arno Massee / Photo Researchers, Inc.
13) Corbis
14) Sheila Terry / Photo Researchers, Inc.
15) Living Art Enterprises, LLC and SPL / Photo Researchers, Inc.
16) Doug Martin / Photo Researchers, Inc
17) Oxford Scientific
18) Anthony Gray
19) Jesús Tarruella / age fotostock
20) Jeffrey Coolidge / Iconica
21) ISM / Phototake -- All rights reserved.
22) Stockbyte
23) Getty Images
24) Brand X Pictures
25) Photosindia
26) Jose Luis Pelaez/ Iconica
SOURCES:
American Heart Association.
APS Foundation of America.
CDC.
Cleveland Clinic.
National Heart Lung and Blood Institute.
The Texas Heart Institute.
U.S. Dept. of Health and Human Services Office on Women's Health.