I just saw this news about Doug Brocail. It seems he was very close to a heart attack, but the doctors found the blockage and opened up the artery:

The 38-year-old Brocail, who last pitched Wednesday, had complained of chest tightness that radiated into both arms. He already was being treated for an abscessed tooth and asthma.
Dr. Harry Albers ordered a stress test, which came back abnormal.
“We found a large abnormality on the front wall of the heart, a blockage,” Albers said. “He wasn’t getting significant blood to the heart under stress.”

Here’s wishing him a speedy recovery.