The spiritual leader of Eastern Orthodox Christians was staying overnight in a New York City hospital after having a stent placement Wednesday afternoon at the conclusion of his U.S. visit, according to the Greek Orthodox Archdiocese of America, writes ABCNEWS.

Ecumenical Patriarch Bartholomew, 81, of Constantinople underwent the procedure at Mount Sinai Hospital following an angiogram that determined the need for the stent, according to the archdiocese. A stent is a tube placed in a clogged blood vessel to increase blood flow.

He was expected to be released Thursday, it said. Further details were not immediately released.

The hospital treatment delayed Bartholomew’s return home to Turkey, which had been scheduled for Wednesday at the conclusion of a busy 12-day U.S. itinerary.

The trip, his first to this country in several years, also began with an overnight hospital stay in Washington when he felt “unwell” a day after his arrival, church officials said.