HEART OF A CHAMPION

Bad heart? If you really believe MacKinzie Kline has a bad heart, then you’re not hearing her thump-thump-thump through life.

She became the top-ranked 14-year-old female golfer in the country even while breathing as if sucking air from the bottom of a sand trap,

She has won tournaments sponsored by Phil Mickelson, even as his green jacket is complemented by her blue lips.

She has two open-heart surgery scars, yet she proudly wears a bikini to the beach.

She has an extremely fragile chest, yet her favorite playground game was -- cover your eyes -- dodge ball.

Bad heart? We should all be so blessed to have MacKinzie Kline’s heart.

Now, that muscle underneath her shirt, that’s another story.

It has never worked right. It’s missing one of two pumping ventricles. This substantially decreases the amount of oxygen in her blood. Her home is near a San Diego beach, but she takes every breath as if she lives on Mt. Everest.

She could never run or swim or jump, so she played golf, dominating the junior circuit, winning so much championship crystal, her parents use the bowls as vases.

But about six months ago, as the courses grew longer and her body grew bigger, her breath grew shorter. After nine holes she was exhausted. By the time she reached the 18th hole, she was sometimes light-headed and loose-gripped and weeping.

Doctors didn’t know what was wrong. Could be her heart, could be the golf, could be fixable, maybe not.

Doctors asked her to undergo immediate catheter surgery for answers. Her parents agreed. But she stared at them through her huge green eyes that glow underneath thick blond hair. And she begged.

Couldn’t they wait until she played in the U.S. Girls Junior Championships this week, and U.S. Women’s Amateur championship next month?

“I don’t know what will happen after that operation,” she said. “I have a chance to take my dreams now, and I want to take that chance.”

Doctors said, fine, but how? How can she play as many as nine rounds of golf in one week when, in her last tournament, she barely lasted 18 holes?

MacKinzie Kline said, just watch.

She stuck an oxygen tank in her bag, and stuck her bag on the back of a golf cart, and her parents won U.S. Golf Assn. approval for both.

She will thus play the Girls Junior Championships in Charlotte, N.C., this week as if she were riding down a hospital hallway.

The oxygen will fit under her nose between shots. She will rest in the cart between holes. It will be ungainly, unusual, but undeniably MacKinzie.

Around her neck she will wear a silver heart given to her by her parents. Between shots, she will grip the heart tightly and pray.

If only she could be as sure about the other one.

“It scares me that I might not ever be the golfer I was meant to be,” she said. “I’ve got to find out.”

Heavy words for someone 5 feet 2, 110 pounds.

The real Big Mac.

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That’s what everyone calls her, “Mac.”

The old hackers at the Encinitas Ranch public course where she plays. The kids at the neighborhood public school she attends.

She is even called “Mac” by her parents, who inserted the capital ‘K’ in the middle of her first name so folks would break off the first three letters and make her sound like something tough.

When she was born with a heart defect that she would not have survived 30 years ago, they knew she would have to be tough.

“We knew it wasn’t going to be easy for her,” said her father, John.

After watching her undergo two heart surgeries before the age of 2, they worried she would never fit in with the other kids. They asked doctors if there were any sports she could try.

Soccer? Too much running. Softball? A home run might exhaust her. Track and field? Be serious.

One of the cardiologists casually mentioned that he was a golfer, offering it as a last alternative.

“We thought, ‘Golf?’ ” John said. “We knew nothing about golf.”

Neither he nor wife Elizabeth had ever played. They still don’t play.

They bought Mac some plastic clubs and she took a few swings and smiled. They drove around until they found a public course, and asked the pro if he could teach her.

“At the time, I didn’t teach 6-year-old children,” said John Mason, the Encinitas Ranch pro. “But one look at her, I made an exception. In her hand-eye coordination, in her swing, you could just see she would be something special.”

With everyone walking slowly and competing carefully, the golf course quickly became one of the places she felt normal.

Not like the school playground, where she couldn’t play on the jungle gym for fear that she would hang upside down and pass out.

Not like the school’s jog-a-thons, where she would always be the one walking at the end.

“I would get out of breath and have to stop,” she said.

Those solitary strolls were perfect for the golf course, where, at age 10, she won the California Junior Girls championship. It was the first of several wins that pushed her, in unlikely fashion, to the top of the national rankings.

“We’re not country-club people, we’re not even golf people,” John said. “But we know what makes our daughter happy.”

Her parents set up a driving net in the small backyard of her home, much to the dismay of neighbors who complained when she was banging balls off metal frame well into the night.

Her coach helped set up a putting green in her garage, forcing her parents to park the cars in the driveway.

The family even installed a ping-pong table next to the putting green so she could work on her hand-eye coordination.

She was named National Spokesperson for the Children’s Heart Foundation, and her path seemed set.

“Then all this started happening,” Mac remembered quietly.

It started in the spring, and it was swift and scary. The girl who finished everything she started suddenly couldn’t finish the thing she loved most.

One day she would play 15 strong holes, then struggle through the final three.

The next day, she lasted 11 holes before fading.

The next week, it was nine holes.

“All of a sudden she would get beet red and start missing shots she normally made,” said her caddie, Hugh Montgomery. “She just didn’t have anything left.”

On the final holes of a tournament in San Ramon in April, she exhaustedly cried out, “I can’t do this!”

Late in a June tournament in Arizona, she began swinging without thinking, wild shot after wild shot, the lack of oxygen affecting her concentration.

“It was like I would just pull out a club and hit, pull out a club and hit,” she recalled. “I didn’t care. I was so tired, I just wanted to go home.”

Her parents had seen enough, and accompanied her to their doctors for exams. The results were as bleak as they were expected.

She flunked the stress test. She was basically competing with the oxygen level of a mountain climber. Some were surprised she could even walk the course, much less play it.

“The decrease in her oxygenation was noticeable,” said John Lamberti, her heart surgeon at Children’s Hospital of San Diego. “Whether that is related to the increase in her level of competition, or a deterioration in the heart, we don’t know.”

And they won’t know until August, as she successfully fights for one more memorable summer.

“We should have done the catheter three weeks ago, but she really wants to play, and we respect that,” Lamberti said. “As long as she takes precautions, which she is doing, she’ll be fine.”

The oxygen precaution has been so finely tuned, the dial is turned to “4” during hills, and “2.5” on flat ground.

The golf-cart precaution has been a bit more awkward, initially refused by the USGA after the Klines failed to make the request in their initial application.

But after checking medical records and being swarmed with complaints from a group including Casey Martin -- a former pro golfer with a deteriorating leg who won a Supreme Court decision that allowed him to use a cart on the PGA Tour -- the USGA relented.

“We hate to deviate from our rules, but this is a pretty special case,” said Marty Parkes, USGA spokesman.

How special? She was the last qualifier at her site for the U.S. Girls Junior and U.S. Women’s Amateur.

How special? At an age when most girls are afraid to stand out in a crowd, this one is willing to be stared at by an entire gallery, which will surely follow her this week as she rides her cart and sucks her oxygen.

Every breath she takes, they’ll be watching her.

“I can’t imagine how hard that must be for her with all the distractions, it was so hard for me,” said Martin, now golf coach at Oregon. “But at least her biggest distraction is gone. Now that she has the cart, she can go for it, and she deserves that chance.”

Mac shook her head and said, “Yeah, sometimes I feel funny. I just hope everyone understands, this is the only way I can play.”

Is it any wonder that, after the women’s amateur qualifying round in Whittier, caddie Montgomery, a 45-year-old former Naval officer, openly wept?

“There is so much going on here,” he said. “It’s not just about golf anymore.”

It’s about a piece of a paper Mac keeps on her bedroom mirror that reads, Some people dream of success while others wake up and work hard for it.

“Sometimes I have to sleep a lot,” she said. “But when I’m up, I’m going.”

It’s about a song that Kline keeps in her iPod, from Queen, about rocking the world. “When I hear that song, I think, that would be cool, to rock the world,” she said.

It’s about two more tournaments before a day of medical reckoning, two more chances to grab that silver heart and say that little prayer and believe that there is no rough too deep, no green too fast, no thump-thump-thump too faint.

“It’s funny, but Mac always says that she’s lucky to have found golf,” said Montgomery, sighing. “You ask me, golf is lucky to have found her.”

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Bill Plaschke can be reached at bill.plaschke@latimes.com. To read previous columns by Plaschke, go to latimes.com/plaschke.