The normal range for a healthy heart is about 60-70 percent, said Dr. Brian Bruckner, the lead research investigator of the stem cell procedure Clegg later received at Methodist DeBakey Heart and Vascular Center in Houston. Using mixed cell populations rather than focusing on one kind of stem cell, Aastrom saw dramatic success in helping facilitate healing at the site of a break in cases that had already received to at least two attempts to fix the problem, Dunbar said.\n