The internal mammary arteries (IMA) that run along the inside of the chest wall make ideal conduits for coronary artery bypass surgery. Studies have proven that an IMA alone or in addition to saphenous leg veins contributes significantly to short- and long-term survival. So when a 2009 review of 541,368 coronary bypass operations performed in 745 U.S. hospitals from 2002 to 2006 showed that more men than women were offered this lifesaving option, the researchers were perplexed. IMA is considered the gold-standard bypass graft, and there are few reasons it should not be used. The disparity is "not fully justified on a scientific basis," the researchers said.