El Segundo, Calif. ? Los Angeles Lakers coach Phil Jackson underwent an angioplasty Saturday after experiencing tightness and pain in his chest for about a week.

The procedure to open Jackson’s left anterior descending artery lasted a little more than two hours, team spokesman John Black said.

“There was over 90 percent blockage,” Black said. “The main threat would have been a massive heart attack.”

Black said a bypass operation wasn’t necessary.

It’s possible Jackson, 57, will be able to coach today’s fourth game of the Western Conference semifinal playoff series against San Antonio.

He was to remain at Centinela Hospital Medical Center in nearby Inglewood Saturday night for observation and will undergo further tests this morning.

The procedure was performed at Centinela by Dr. Phillip Frankel and Dr. Vern Hattori of the Apex Cardiology Group.

“If all goes well, he’ll be able to coach the game,” Black said.

Black said it’s also possible Jackson will be able to travel Monday to San Antonio for Game 5 Tuesday night.

“If all these tests go fine, he’ll be cleared to do everything,” Black said. “The procedure went very well. He’s resting comfortably. He’ll be on medication for several months.”

During an angioplasty, cardiologists thread a balloon into the clogged coronary artery and inflate it to push the blockage aside. A stent, or wire-mesh scaffolding, often is inserted to help keep the artery from further blockages. That was the case for Jackson.

Between 15 percent and 30 percent of patients suffer another blockage within a year, as scar tissue grows around and into the stent.

Jackson has coached nine championship teams to tie former Boston coach Red Auerbach for the most in NBA history. Jackson’s teams are 161-58 in the postseason for a record .735 winning percentage, and his 161 playoff wins are the most ever.

He coached Chicago to six titles in nine years and is going for his fourth title in as many years with the Lakers.

Jackson underwent tests Friday before the Lakers beat San Antonio 110-95, cutting the Spurs’ lead to 2-1 in the best-of-seven series.

Doctors wanted to complete all tests Friday, but Jackson decided to wait until after the game. Assistant coach Jim Cleamons ran Saturday’s practice and will lead the team today if Jackson can’t.