The 34-year-old forward's long-term health is not in question, coach Paul Maurice said. Letestu has missed the past six games with an undisclosed injury.
Myocarditis, usually caused by a viral infection, can affect the heart muscle, reducing the heart's ability to pump and causing rapid or abnormal heart rhythms, according to the Mayo Clinic.
Letestu signed a one-year, $700,000 contract with the Jets on July 2 and has no points in seven games. He has 210 points (93 goals, 117 assists) in 567 NHL games in 11 seasons with the Pittsburgh Penguins, Columbus Blue Jackets, Edmonton Oilers and Jets.
The Jets (6-7-0) also will be without forward Patrik Laine (lower body) against the San Jose Sharks at SAP Center in Friday (10:30 p.m. ET; NBCSCA, TSN3, NHL.TV). Center Bryan Little is questionable for Friday, but Maurice said his issue is not related to the concussion that sidelined him for the first nine games of the season.
