Speaking from his home in Epsom, Mr Casey said: "My recollection of that day is limited, I don't remember leaving the house.
"My first memory is of waking up in hospital, people were talking and I remember thinking I must have had a heart attack.
"It's quite emotional. It brought home, if you know what to do then you can help but if you don't then you could watch someone die right in front of you.
"I am grateful to Aziz, the paramedics, the passerby who stopped and helped, everyone who was involved - without them I wouldn't be here today."
Mr Casey has been riding bikes for almost 30 years.
His doctor explained that he suffered a problem with his coronary artery, blocking the blood supply to the heart and causing cardiac arrest.
"Eight minutes with no heartbeat could have left me in serious trouble. Luckily I had people around me who knew what to do and were properly trained.
"Before I get back on to my bike I will be taking a refresher course in CPR and recommend anyone who reads this to do the same."
Mr Casey and Mr Bharuchi, 36, are both members of Eden Cycling Club, but until last Tuesday had never met.
The physiotherapist said the group were a few minutes from finishing their ride when he saw Mr Casey, who was towards the front of the pack, drop dramatically to the ground.
"He hit the kerb at a right angle and went straight over the handlebars. I immediately got off my bike and ran towards him but I couldn't feel a pulse, he wasn't breathing and he was turning pale," said Mr Bharuchi.
"After placing my shirt beneath his head I started doing resuscitation.
"Then an angel arrived. A complete stranger who stopped said he was a doctor and started doing chest compressions. When he got tired someone else from the group took over and we kept going until the ambulance arrived.
"I am lucky that because of my job I am trained in CPR, so I switched off and did what I had been taught. It wasn't until afterwards that I realised I had been a part of saving someone's life."
Chris Denny, emergency medicine specialist at Auckland District Health Board said: "Technically when your heart stops beating your death begins.
"I chatted with the team who worked on this gentleman and the chain of survival was crucial, his friends and colleagues and medial team did an amazing job."
Bridget Dicker, St John clinical research fellow, said: "For every minute of cardiac arrest without CPR or defibrillation, a patient's chance of survival falls by 10-15 per cent. This makes the community and bystander response integral to survival."
Chain of survival
• Cyclist Paul Casey suffers a heart attack at 7am and falls to the ground. His teammates gather around him, forming a protective circle. Fellow cyclist Aziz Bharuchi begins performing CPR.
• A passing cyclist stops and offers to help - he is a qualified doctor who begins chest compressions, which are continued by teammates.
• Two members arrive from the Auckland Rescue Helicopter Trust, which has a base nearby. Paramedic Marcel Driessen takes over the treatment and a defibrillator successfully restarts Mr Casey's heart.
• St John Ambulance transports Mr Casey to Auckland City Hospital in critical care. His body temperature is lowered to avoid any further potential brain damage. He awakes with no signs of damage to his brain or other organs.
