Former Pennsylvania Gov. Tom Ridge was recovering Friday after suffering a heart attack the day before, his wife said.

"It's going to be day-by-day," Michele Ridge said in her first public comments since his hospitalization a day earlier.

Her husband "remains in critical condition but he's resting comfortably" and responding to his doctors, she said in the statement. "And we all know what a fighter he is."

The former governor, 72, was transported to a Texas hospital Thursday morning after he contacted staff at the hotel where he was staying and asked for medical assistance. He had been attending the Republican Governors Association conference at the JW Marriott in Austin.

Ridge, who was also the first U.S. Homeland Security secretary, remains at Dell Seton Medical Center at the University of Texas, where he underwent cardiac catheterization, a procedure designed to help diagnose and treat heart problems.

The family had not initially disclosed Thursday that he'd had a heart attack. But news of his hospitalization stirred widespread concern and well-wishes among friends and former colleagues in government and politics.

Generally, someone who has a heart attack experiences a rupture in the waxy plaque that lines the coronary arteries of most older people. The body responds to this type of rupture by forming a clot, which blocks blood flow to the heart muscle and causes its cells to start dying.

If the damage is treated in time, most patients survive. At Dell Seton Medical Center, 85 percent of patients survive for at least 30 days following a heart attack, according to the most recent data from the federal Centers for Medicare and Medicaid Services.

A catheterization involves threading a tiny camera into the coronary arteries to inspect the damage. In most cases, a cardiologist would also insert a balloon to open the blockage and then prop it open with a cylindrical device called a stent — a routine procedure.

The Ridge family did not specify whether that second step was taken.

Michele Ridge said Friday that she wanted to thank the first responders who "worked heroically" to rush her husband to the hospital and the doctors, nurses, and others who cared for him there.

"It is difficult to find the right words to appropriately thank all of the men and women who continue to provide Tom with such tremendous care. I am thankful Tom was in Austin when this happened and close to world-class medical facilities," she said.

Staff writer Tom Avril contributed to this article.