NEW YORK —  Daniel Walker was on his final lap jogging in his high school gym class when he collapsed, his flawed heart giving out on him.

Days later, his heart at a standstill, kept alive by a bypass machine, it began beating again. The 17-year-old's parents called it divine intervention. His physicians were no less amazed.

"I've been a surgeon for 10 years, and this is probably one of the most incredible things I've ever seen," said Dr. Abeel Mangi, one of Walker's cardiac surgeons at New York-Presbyterian Hospital Columbia.

Walker's father described his son's recovery in spiritual terms. "God turned around, put His hand on my son, and recharged him," said William Walker, 58, a retired sanitation worker.

His son's ordeal began Jan. 19 when he collapsed in gym class. The younger Walker suffered from a rare congenital heart flaw that left his coronary artery pinched, giving him only 10 percent of normal heart capacity. He was shuttled to two hospitals before finding himself at Columbia, waiting for a heart transplant, attached to the bypass machine.

Walker's cardiac surgeons said they could not account for the young man's recovery.

"It's a miracle," Mangi said. "There's really no other way to put it."

Two days after it began to beat on its own, surgeons were able to fix the flaw in Walker's heart, increasing its capacity to 60 percent.