Key Points:

A medical equipment salesman gave the ultimate demonstration of his lifesaving machinery when an elderly man had a cardiac arrest in a hardware store yesterday.

A St John Ambulance volunteer for 20 years, Gavin MacDonell, was showing staff a heart defibrillator - used for "zapping" hearts back into action after cardiac arrest - when he was called into action at PlaceMakers in Albany.

He managed to restart the heart of the pensioner who ambulance crew later described as "clinically dead" before Mr MacDonell's intervention.

"One of the women that works there came running into the corner and said 'quick, quick, quick, get that defib-y thing' - she knew it was there - 'someone's collapsed on the ground with a heart attack'," Mr MacDonell, 42, explained.

"So with that we grabbed that and went looking down the aisles and found him."

Mr MacDonell, a salesman for medical technology company Weinmann, said two people were performing CPR on the man in front of a crowd of people when he arrived about 11.15am. He said the man, who was in his 80s, had a scar on his chest from previous surgery. His heart was not registering a beat when the two chest patches from the defibrillator were first attached.

"Once we got a shock into him he started to gag ... and we thought 'this bloke's coming back!' The people in the shop that were working there were just blown away"

Mr MacDonell was modest about his lifesaving actions.

"It was just one of those things. I don't consider myself the hero or anything like that. It's just lucky that I had the machine and I was there.

"I know I was here and I did this but I think the two main heroes were the two that did CPR and got down and got into it ... I was just lucky to be there with the tool."

While he has attended many cardiac arrest calls in his 20 years with St John, Mr MacDonell said it was different to encounter the emergency in "real life".

Asked if he closed the sale, Mr MacDonell said everyone got distracted with the emergency but he would be going back for a follow up visit.

The man was taken to intensive care at North Shore Hospital and is expected to recover.

Shocked into life

* Defibrillators deliver electric shocks through two adhesive pads to the chest of people in cardiac arrest.

* The device works by stopping abnormal rhythms and gives the heart a chance to restart beating with a normal rhythm.

* The sooner the shock is delivered, the greater the chance of survival.