CHICAGO, Ill. (WGN) — Two sisters in suburban Chicago put years-old lessons to the test and saved their dad’s life after he collapsed at home with a heart attack.

Mark Sagan was doing some painting around the house on January 15 when he felt something come over him.

“I think I was getting lightheaded or something and walked downstairs and said, ‘You better call somebody, I don’t feel well,’ and that was it,” Sagan said. “I went down, turned blue and that is the last I remember.”

In that moment, Sagan’s daughters — who were home from college — jumped into action.

“The only thing I was thinking when you’re not breathing what do you do? You do CPR,” Cora Sagan said.

Kalie called 911 as Cora started chest compressions, which she’d learned as a student at Deerfield High School.

In 2014, Illinois mandated high school students receive AED and CPR instruction as part of their health curriculum.

The law was named for Lauren Laman, a St. Charles, Ill. student who suffered cardiac arrest but didn’t receive immediate attention from bystanders. Her parents envisioned future generations trained in CPR.

“If they learn it in high school and they continue down the generations, we’re going to have rooms full of people that are going to know what to do,” mother Mary Laman said in 2014.

But long before it was law, Marc Pechter was teaching the skills at Deerfield High School, and the lesson stuck with the Sagan sisters.

“I knew the chest compressions part which is the part you want to know for a heart attack, but it came back so fast because I haven’t thought about it much since high school,” Sagan said.

First responders eventually took over compressions and used a defibrillator at the hospital.

Doctors discovered a 100% blockage in Sagan’s left anterior descending coronary artery, which NorthShore cardiologist Dr. Jonathan R. Rosenberg said can “definitely be a fatal situation.”

“There is no question that Mr. Sagan’s daughters giving him CPR is what saved his life. Not having CPR for an extended period of time, even a few minutes, can cause lack of oxygen to the brain and can cause someone to die,” Dr. Rosenberg said.

A stent was placed and restored blood flow. Still, Sagan’s chances for survival were less than 40%. For those who do not receive bystander CPR or AED assistance, the survival rate is 10%, compared to 50% for those who do.

The Sagans just celebrated Mark’s birthday, saying they’re grateful to be able to do so together.