The Oregonian newspaper reports (http://is.gd/ovLF9e ) Dr. Joaquin Cigarroa was just a few steps behind the man who collapsed Saturday. The doctor immediately performed CPR.
Cigarroa and another cardiologist on the walk, Brad Evans, pumped on the man's chest and detected spontaneous heart beats.
Paramedics who had struggled to get to the scene because of the big crowd and a closed bridge then used a defibrillator to restore the man's heart rhythm.
The unidentified man was taken to a hospital. Cigarroa told the paper he heard the man will survive and is neurologically intact.
The event drew 8,000 participants.
Information from: The Oregonian, http://www.oregonlive.com