AUSTIN (KXAN) — As Austin ISD students head back to class next week, one P.E. teacher has a life-saving lesson plan ready to go. It’s because he spent the summer recovering from a massive heart attack — a type that strikes nearly one-third of patients.

Doctors took a scan of Justin Ballou’s heart back in May, moments after the 31-year-old Paredes Middle School physical education teacher had a massive heart attack.

“This is all muscle here that’s not getting blood. So at least 40 percent of your heart was being getting shut down,” said the cardiologist who performed Ballou’s surgery.

The blockage in his vessel was so large doctors spotted it right away. They are called STEMI (ST-Elevation Myocardial Infarction) heart attacks because health workers can clearly see them on a scan.

“I never knew that with me being in shape that I would have a heart attack,” Ballou said.

He also did not know that it would strike in the middle of a high-intensity interval workout. Staff members at his gym quickly jumped into action performing CPR and using an automated external defibrillator.

“I just dropped the band and I fell back and blacked out. I was gone,” Ballou said. “They got out the AED machine and put the pads on me and shocked me. And, that’s when I came back.”

Looking back, Ballou said there were signs, especially while working out, before his heart attack.

“I would get shortness of breath and sharp pain in my chest,” he said. “But I would calm down, move to the side and catch my breath — and it would go away. But every time I would get active, I would feel that same pain.”

Doctors say STEMI heart attacks are the most lethal because the artery is 100 percent blocked, cutting off blood flow to a large portion of the heart. Dr. Robert Wozniak led the emergency team at St. David’s North Austin Medical Center that day. He said of all the heart attacks, STEMIs strike about 30 percent of the time and patients usually feel symptoms before they hit.

“Some of those symptoms could be a discomfort anywhere in their chest anywhere between their jaw and navel,” said Wozniak, who is the director of Cardiology at the hospital. “Some discomfort that happens with physical activity or emotion should cause you to pause.”

As a P.E. teacher, Ballou is required to know CPR. He has also taught the importance of learning the life-saving training to his students. He said when school starts next week, he plans to drive that lesson home with his own personal survival story.

“In my situation, someone that it was done on and is here today because of it, I think they would take my story seriously,” Ballou said. “A lot of people don’t know, especially kids. They don’t know what to do in this situation.”