A 62-year-old cyclist went into cardiac arrest while participating in the Five Boro Bike Tour Sunday but was stabilized by a fellow rider and FDNY rescuers who treated 44 patients during the event, officials said.

James Hamilton of Bethany, Conn., lost consciousness and was clinically dead after he fell from his bike while cruising with his wife on the upper level of the Queensboro Bridge about 9:50 a.m., authorities said.

Another cyclist quickly performed lifesaving CPR as onscene medics arrived, FDNY officials said.

Emergency Medical Service technicians Valerie Vera-Tudela and Beth Tichman used a defibrillator to revive Hamilton, who regained a pulse and was taken to Mount Sinai Hospital of Queens in guarded condition, the FDNY said.

By the time he was transferred to Mount Sinai Medical Center in Manhattan, Hamilton was talking and breathing on his own, officials said.

A total of 44 people required medical attention during the 42-mile tour that attracted about 30,000 riders, said Deputy FDNY Chief Katherine Fuchs.

The injuries ranged "from bumps and bruises to [Hamilton], who was clinically dead," said Fuchs. "It's been a very busy, crazy day."