"Michael Tilson Thomas had a successful heart operation at the Cleveland Clinic and is recovering well. The doctors have called the procedures a complete success and have said that his heart is performing at 100%. He is currently recuperating at the Clinic and will return to the San Francisco area in the near future where he will spend the summer convalescing and preparing to open the 2019–20 seasons of the San Francisco Symphony (September 4) and New World Symphony (October 12)." Shuman PR
That below posted on June 5
NEW YORK, NEW YORK (June 4, 2019) — Michael Tilson Thomas announced today that he is withdrawing from all engagements beginning June 17 until September 3 in order to undergo a cardiac procedure. The operation, which will take place in Cleveland, is scheduled to follow his performances of Mahler’s Symphony No. 9 with the San Francisco Symphony on June 13, 14, 15, and 16.
“I deeply regret missing concerts and projects that I have been greatly anticipating,” said Tilson Thomas. “On the advice of my doctors, I need to undergo this procedure at this time in continuation of treatment for a heart condition I have managed for many years. I expect to make a full recovery in time to return to the San Francisco Symphony for the opening of my 25th season as Music Director.”
Previously scheduled engagements from which Tilson Thomas is withdrawing are performances with the San Francisco Symphony and appearances at the Music Academy of the West including concerts with the London Symphony Orchestra.