LYNN – What happened to Penny Centrella could be described as the ultimate payback.The Lynn woman adopted a dog from the Northeast Animal Shelter in Salem last year, a mixed-breed puppy named Zeus. On Friday, July 13, the dog repaid that debt in full by saving her from certain death.Centrella was getting ready for a doctor’s appointment when she began feeling dizzy and collapsed face down in the bathroom of her 51 Belmont Ave. home. Sensing something amiss, Zeus licked, pawed, barked, and eventually nudged his owner until she rolled over and regained consciousness long enough to dial 911.When paramedics arrived, they found Centrella on the floor, suffering from a heart attack. Zeus was at her side.At North Shore Medical Center, surgeons quickly went to work reviving her heartbeat. A major artery in Centrella’s heart was 85 percent blocked. The surgeons inserted a stent.”The doctors told me if the dog had not woken me up, I would have been dead before my husband got home from work,” said Centrella, who has been recuperating at home. “What more can I say? Zeus is a hero. I told him from now on he can have anything he wants, no matter what.”Centrella, who owns and operates a mobile dog grooming service called Whisker Waggin, said it seems fitting the traumatic late-morning incident occurred on Friday the 13th.”I had no idea that I even had a heart problem. I thought the dizziness was caused by my diet because I had gastric bypass surgery and lost more than 100 pounds,” she said.Zeus, a cross between a Labrador retriever and a pointer, is just over a year old. Centrella and her husband, Robert, couldn’t be more pleased to have him as part of the household.”Zeus was spoiled before this, but after everything happened, I bought him the biggest steak, and I told him he could have as many toys as he wanted at the pet store,” she said. “Dogs are wonderful.”