Scott Olson was asleep in the quiet darkness of his daughter’s home in north central Minnesota, when the lightweight vest he’d been wearing detected a dangerously erratic heartbeat. Without ever waking Olson, his LifeVest sounded alarms and delivered a jolt of electricity to his heart, saving his life.

He only knew what had happened after his granddaughter, Americiss, heard the alarms and woke him.

“I didn’t even feel the shock,” Olson said. “I just heard my granddaughter calling my name.”

Olson, 55, had been prescribed the wearable defibrillator only three weeks earlier by Dr. Raed Abdelhadi, an electrophysiologist at Abbott Northwestern Hospital in Minneapolis. The LifeVest, manufactured in Pittsburgh by ZOLL Medical Corp., has been on the market since 2001, when it was approved by the U.S. Food and Drug Administration. It’s meant for people whose hearts are at risk for sudden cardiac arrest but who for one reason or another have not been given an implantable cardioverter defibrillator (ICD).

Abdelhadi said Olson’s heart was weakened and he had an abnormal arrhythmia, but there was hope that he might improve with medication. The vest was meant to provide a security blanket.

“Not every shock means a life saved,” Abdelhadi said recently. “But looking at his electrocardiogram, it’s good it did. He likely would have died in his sleep.”

According to ZOLL, 100,000 LifeVests have been prescribed worldwide since the device won FDA approval. Abdelhadi said he has prescribed three or four over the past six months. It is intended to be used by people in four categories: someone with a weak heart at risk of cardiac arrest, but who doctors think may recover; someone who should get an ICD, but is temporarily prevented from doing so; someone who is waiting to complete a full evaluation for an ICD; or someone who is close to getting a heart transplant. Determining the best candidates for the device is not an exact science, he said.

“It works the majority of the time — when the patient is wearing it appropriately,” Abdelhadi said.

How it works

The LifeVest is worn under clothing. It comes in two pieces — a vest that contains electrodes and a small monitor worn at the waist or from a strap. Small sensing electrodes monitor the patient’s heart. If a life-threatening rhythm is detected, the device alerts the patient before delivering a treatment shock. A conscious patient has the option of touching a button to abort the jolt. If the patient does not respond, the device releases a gel over larger therapy electrodes at the back that deliver a jolt to return the heart to a normal rhythm. The device can deliver multiple jolts.

Data from earlier clinical trials shows the device is safe and delivers a lifesaving jolt. Other trials to determine whether patients who have recently had a heart attack could get better while wearing the device are underway, Abdelhadi said. The main issue, he said, is patient compliance with all the instructions — sometimes they just don’t do everything they are supposed to do. Still, he said, it is a good option for some patients.

“We’ve been more and more at least offering it to patients,” he said.

According to the company, the device is covered by most insurance plans. A ZOLL spokesman said he could not provide data to show how many Minnesotans are wearing LifeVests, or how many lives — like Olson’s — it has saved. According to ZOLL, the device has a first treatment shock success rate of 98 percent.

On Monday of last week, Olson received an ICD at Abbott Northwestern. The former house painter will no longer need the thin fabric vest or sensor that he wore on a strap for less than a month.

But he and his daughter are convinced that it saved his life — and just in time.

“When they gave it to him, they didn’t know if he was going to be shocked or not. We didn’t even know if he needed it,” Jessie Olson said. “Then it happened. I’d recommend it to anybody. The fact that he had it on him was really good.”

Said Scott Olson: “It saved my life, obviously.”