Robert McGrath says he thought he was going to die last week at the hands of Edmonton police.

McGrath's wife, Stephanie Boswell, blames herself for calling 911 and inviting trouble into their west Edmonton home.

McGrath, 23, was diagnosed four years ago with congestive heart failure. He has been unable to work ever since.

But until last week he had been managing his health condition, he said. He started feeling unwell at the beginning of the week, then lost consciousness early Wednesday morning.

McGrath's wife panicked and called 911. Boswell said the paramedics and firefighters who arrived at their tiny basement apartment were very helpful and professional at first as they treated her unconscious husband.

Robert McGrath says he was assaulted by first responders. (CBC)

"They were definitely concerned, considering he has a heart problem and he's unresponsive at this point," she recalled. "They're smacking him and nothing, flashlight in the eyes, nothing."

The first responders decided to use a technique that involved pinching the back of McGrath's neck in an attempt to get him to respond, Boswell said.

"When they did that he sat straight up and took a big breath of air," she said. "And then he was out again, sitting up."

A firefighter and a paramedic crouched on the floor behind McGrath, each using a knee pressed against his back to keep him upright.

Boswell said the paramedic repeated the technique and her husband came to with a start. His hands and arms jerked backwards. The back of her husband's hand made contact with the firefighter's cheek, she said.

That's when things turned ugly, she added.

'You just assaulted somebody'

The whole mood changed, she said. "They tackled him, screaming at him, 'You just assaulted somebody. Now we've got to get the cops. You're doing this the hard way.' "

McGrath said he remembered little up until that point. But then he felt like he woke up in a nightmare.

"You're knocked out," he said, "and the first thing you're coming to is people on top of you, bending your arm behind your back. All I remember is screaming, 'Let go of my arm, let go of my arm.' "

Robert McGrath's wrist showing red marks and bruising he says were caused when police put him in handcuffs. (Facebook)

McGrath is a mountain of a man. He weighs 300 pounds and is six-foot-three. His wife thinks McGrath's size may have caused the first responders to panic.

"Because he is such a big guy and none of them are big at all," she said. "They were all smaller men."

McGrath said he was unable to move or resist.

"I literally couldn't," he said. "I had people standing on my legs, both my arms pinned behind my back. There was a knee on my neck pinning my head to the ground."

Then police arrived. McGrath said the officers treated him "like I was a murderer or a pedophile or something." They pulled his hands behind his back and handcuffed him, and screamed at him to "be a f***ing man," he said.

A half-dozen officers pulled McGrath up the steep stairs from his suite, while his wife sat shaking in fear in their living room.

"It honestly sounded like they were trying to take down a murderer or a gunman or somebody," she said. "They weren't talking to him like he was just unconscious. They were talking to him like he'd been conscious the whole time swinging fists."

McGrath said he was dragged across the road to a gurney outside an ambulance.

They weren't talking to him like he was just unconscious. They were talking to him like he'd been conscious the whole time swinging fists. - Stephanie Boswell

"They threw me onto it, and that's when my ICD went off for the first time," he said

After McGrath was diagnosed with congestive heart failure in 2012, an implantable cardioverter defibrillator, or ICD, was inserted to regulate his heart rate. It's designed to generate an electrical shock if the heart is beating too fast or too slow.

Until last week, McGrath said his ICD had never shocked his heart. At first he thought police had used a Taser on him. Then he felt a second shock.

'You're going to kill me'

"That's when I realized what it was," he explained. "I yelled at them, 'That's my ICD going off. You're going to kill me if you keep doing this.' And they did not care whatsoever. No paramedics tried to get involved, knowing that I have heart problems, knowing that I have the ICD."

He said two officers were still holding him down on the gurney when his ICD delivered a third shock.

"And that's when they started rolling me into the ambulance," he said. He was taken to hospital and released hours later.

Closeup shot of Robert McGrath's face showing red marks around his eye. He said he sustained the injury when police banged his head against a wall. (Facebook)

Doctors at the pacemaker clinic told him later that over a 10-minute period during the ordeal, his heart raced at 195 to 205 beats per minute. The norm is between 70 and 80 beats per minute.

Police did not formally arrest McGrath or charge him. McGrath said he has no criminal record.

"I've never been arrested," he said. "I've never even gotten a speeding ticket. They treated me like I was some convict."

McGrath launched a formal complaint with the Edmonton Police Service. An EPS spokesman confirmed the incident is now being investigated by the Professional Standards Branch.

McGrath also complained to Alberta Health Services about the treatment he received from the first responders. In an email, spokesman Kerry Williamson said: "We are aware of the complaint, are currently reviewing the call and have also connected the patient to Alberta Health Services Patient Relations. For the privacy of both patient and staff, we are unable to provide any further details."

'It's sad he got treated this way,' wife says

The events have changed the way they view police, McGrath and his wife say. McGrath said he was brought up to think of law enforcement as 'the good guys.' He recalls his parents taught him: "You respect them, they'll respect you" and "You don't get in trouble, they're not going to give you trouble."

But "in the matter of an hour, I had my complete opinion changed" about police, McGrath said.

"I can't look at police the same way anymore. I can't have that kind of trust because I feel almost betrayed and traumatized by how I was treated."

They could have ended my life. Were it not for my ICD, I would be dead. I would have had a massive heart attack right there. - Robert McGrath

Boswell said she hasn't slept much since the incident and has been suffering panic attacks. Her eyes glistened with tears when she admitted she feels guilty for calling 911.

"It's sad he got treated that way," Boswell said. "That's the only word I can think of. It's sad."

But McGrath is angry.

"They could have ended my life. Were it not for my ICD, I would be dead. I would have had a massive heart attack right there," he said. "We called for help. But instead we got more trouble."