No one appreciates life more than those who have danced with death, and those who have watched from the sidelines, waiting to cut in.

It’s cliche to say that it changes people, but it does. The stress of a deadline or the annoyance of a project being delayed suddenly seems trivial. The sensation of a lemon drop melting on your tongue or the caress of your lover’s toe on your ankle becomes utterly important.

For Deborah Heffernan, now 49, and her husband, Jack, the dance began five years ago, in the middle of Deborah’s yoga class in Cambridge, Mass. She was languidly stretching, her back pressed against the polished floor, when she felt her chest constrict, like someone was tightening her breastbone with a vise.

“I am having a heart attack,” she calmly told her instructor. “I want you to call 9-1-1.”

It wasn’t supposed to happen to her. She never smoked. She ate her vegetables. She drank soy milk. She exercised regularly. She scaled mountains for fun. Her healthy lifestyle, her doctors told her later, is why she lived.

“I was in shape for the fight of my life,” Heffernan said, lying on a wicker couch, in the house she and Jack share in the western Maine town of Bridgton. “Most Americans are not.”

She vividly chronicles that fight in “An Arrow Through the Heart: One Woman’s Story of Life, Love, and Surviving a Near-Fatal Heart Attack,” recently published by Free Press, a division of Simon & Schuster.

It’s the story of the first year after the attack, from the moment the doctors wheeled her into the operating room, with Jack running behind them shouting, “Fight it, baby, fight it,” to the family reunion that took place on the one-year anniversary.

It was a year of trepidation and courage, change and constancy. Jack would wake in the middle of the night to poke Deborah, just to see if she was still alive. Deborah, normally strong and feisty, would shrink away from people on cellphones, for fear that the radiation would cause “the box” in her chest to misfire.

In that crucial first year, she and Jack decided to sell their apartment outside Boston and move to their lakefront home in Maine full time. She saw the changes in her life reflected in the changing seasons. With each blooming flower, each turning leaf, she grew stronger.

“It was a place for her heart and soul to heal,” Jack said.

There was a lot of healing to do. The emergency open-heart surgery that occurred after her yoga class left her with half a heart and an arrhythmia that needed to be corrected with a cigarette-lighter-size implant tucked under the skin above her breast. When it fired, it left her momentarily unconscious.

She also had a lot of healing to do in her “spiritual” heart – from past hurts, from feelings swept aside. The cozy home that she and Jack created under a canopy of pines on Sebago Lake provided the solace she needed. There, a stream of friends and family kept watch over her.

“The important thing is for people to seek out love in their lives, especially when they’re healing – by love, I mean kindness, compassion, generosity, thoughtfulness, humor and forgiveness – that is love,” Deborah said. “Too often when people are ill they retreat. Instead, it should be a time to listen to their heart and find love in themselves and be grateful for that.”

“An Arrow Through the Heart” is, more than anything else, a love story. When you meet Deborah and Jack, the bond they share is immediately clear. You can see it when he looks at her and can’t stop grinning. It shows in the easy way they laugh. In the way they finish each other’s sentences.

“The incredible love we had sustained us,” Deborah said. “It gave us the strength to fight when we had to.”

But even a love like theirs doesn’t come without complications. When they married, Deborah was 37. Jack was 50. He was divorced with five children. She had never been married. His children weren’t thrilled about the two of them getting together. Her father wasn’t sure what to think about his daughter marrying an older divorc?. In the year that followed Deborah’s heart attack, these lingering reservations gradually disappeared.

“I think it had something to do with our love story,” Deborah said. “Everyone loves a good love story and never wants to see it end. I think that touched everyone. What happened to us touched other people’s fears of abandonment.”

It also left people reeling. If something like this could happen to Deborah, a successful businesswoman who exercised, ate well, didn’t smoke and only occasionally splurged with one drink before dinner, surely it could happen to them.

“The idea that this happened to someone who seemed to have it all together and was living a healthy life struck a chord with members of my generation,” Deborah said.

The common perception is that heart attacks happen only to men, or they happen only to people who eat potato chips and pepperoni pizza every day and wash it down with beer and cigarettes. According to the American Heart Association, cardiovascular disease is the No. 1 cause of death among American women. It kills more women than the next seven causes combined. Not breast cancer. Heart disease.

“I didn’t ask for this and the fact that others ask for this makes me mad,” Deborah said. “Fifty to 70 percent of cardiac fatalities can be attributed to known risk factors – cholesterol, smoking, inactivity.”

The disease affects one in every two women, yet many know little or nothing about it. Had she not read an article about heart attacks in an airline magazine, Deborah never would’ve recognized the symptoms. This is one of the reasons why she wrote this book.

“It’s not about me at all – it’s about my mission to save women’s lives,” she said. “The book has got to reach women because I can’t.”

During a recent interview, Deborah had to lie down because she had been to the doctor earlier that morning. She tires in the afternoon. Though mountaineering was one of the passions she and Jack once shared, she can no longer climb higher than 7,000 feet. When she climbs now, she must stick to certain parameters. But Deborah isn’t going to let it get her down.

“I go slowly, but I go,” she said. “I’m the one who turns lemons into lemonade. I did it and I’m so glad for that. I did it and it was grand and this is just a change.”

It’s one of many that the couple have assimilated into their lives. But “lives” is the key word here. Sure, Jack still wakes up to poke Deborah in the middle of the night. And Deborah sprints through the doorways of stores so the anti-theft devices won’t set off “the box” in her chest. But these are small things. Being alive is one big thing. Being together is the other.

“That’s the neat thing about partnership and the incredible bond we have,” Deborah said. “I do believe there’s such a thing as two hearts beating as one.”

Jack agreed, as he looked over at his wife and smiled.

“Whatever faces us in the future we’ll address it together, hand in hand, Deb and Jack, Jack and Deb.”