When is relatively moderate physical activity like mowing the lawn enough to cause a heart attack?

Bob Furlong, 53, of South Glastonbury found out. Physical exertion can make a partially blocked artery suddenly become fully blocked.

“It’s like a scab inside the heart artery, so then the scab rips open and it attacks you,” says Dr. Eric Oligino, a cardiologist at the Heart & Vascular Institute at Hartford Hospital. “It makes a 20 percent blockage and goes to 100 percent blockage.”

Furlong, after being taken to Hospital with heart-attack symptoms, went into ventricular fibrillation — a disruption of the heart’s rhythm that prevents the heart from pumping. The result, a heart attack, put Furlong’s life in danger. It took CPR, multiple medicines, a life-support device and 26 shocks to revive him.

“You can see the heart quivering,” says Dr. Tal Azemi, as he evaluated test results. “That’s when he was going into cardiac arrest.”

Furlong was also treated with extracorporeal membrane oxygenation, or ECMO, a life-sustaining device that removes blood from the body (extracorporeal), then extracts carbon dioxide and injects oxygen (membrane oxygenation, or “artificial lungs”) into it.

“I was as close as I could have gotten to death as possible,” he says.

February is American Heart Month.