Tom Signore will take over as pitching coach in Las Vegas until Viola is ready to return. Signore will then return to his job as pitching coach for Single-A Brooklyn.
Viola had served as the pitching coach for Single-A St. Lucie the last three seasons. This was going to be his first season with the Triple-A team.
The Viola family issued a statement:
"Frank Viola underwent a recent medical examination during Spring Training. Mets physicians discovered a heart condition that needed to be corrected as soon as possible. Frank will undergo surgery next week in New York. The family welcomes all prayers but requests privacy during this time."