According to Pedro Moura of ESPN Los Angeles, former USC defensive tackle DaJohn Harris revealed at USC's pro day Wednesday that doctors found a small hole in his heart during a physical exam, which is why he did not work out at the NFL combine last month. Per Moura:
Harris, projected as a midround pick in April's draft, visited an Arizona cardiologist with agent Joe Panos shortly after the combine and found that the hole was normal and natural. He said his doctor has since emailed all 32 NFL teams, alerting them of his status and permitting him to work out as usual.
Harris, a two-year starter for the Trojans, has a condition known as a PFO, or patent foramen ovale, discovered after NFL doctors ordered him to undergo an EKG and echocardiogram in Indianapolis.
The condition is a small hole located in the heart that all humans have until birth that assists with blood flow. Most holes close upon birth, but in roughly 25 percent of humans, the hole never completely closes naturally and for those people it is not typically treated as an issue.
You can read all of Moura's story here.