Jimmy Kimmel Brought to Tears Describing Newborn Son's Open Heart Surgery During Monologue

Jimmy Kimmel was on the verge of tears during his opening monologue Monday as he described the terrifying experience immediately after the birth of his son ... who needed life-saving heart surgery.

Jimmy's son, Billy, was born a little over a week ago and seemed fine at first ... but hours later was diagnosed with a heart condition that required open heart surgery.

The comedian says Billy's pulmonary valve was completely blocked, and he also had a hole in the wall between the left and right sides of his heart. His first open heart surgery was apparently a success ... but Jimmy says he'll have to have more operations in the future.

It's a pretty emotional clip ... grab the tissues.