Biddeford High senior Hannah Gosselin warms up between innings during a May 31 game against Scarborough. Gosselin had a heart procedure on April 1 after being diagnosed with an arrhythmia that caused her heart to surge to 280 beats per minute during one episode earlier this year. Derek Davis/Staff Photographer

BIDDEFORD — Hannah Gosselin felt “funny.”

That was how the Biddeford High senior described the discomfort she began to feel during a basketball game on Jan. 8. Discomfort turned into chest pain, a ramped-up heart rate, difficulty breathing, and a trip to the hospital.

Gosselin, 18, soon had a diagnosis: supraventricular tachycardia (SVT), a condition that causes a heartbeat to suddenly and drastically accelerate. Three more episodes followed, leading to a heart procedure in early April. Gosselin, a standout second baseman on one of the top high school softball teams in the state, wondered if her season was over before it had started.

“I was worried about that,” she said. “These girls are my family, I’ve been playing with them since I was 9 or 10.”

Chantelle Bouchard, a senior catcher for Biddeford, was playing alongside Gosselin on the basketball court that January night when she looked over at halftime and saw that something was wrong.

“In the locker room, I noticed that she was kind of breathing a little heavy,” Bouchard said. “She just wasn’t herself. She was looking really pale, and I was like ‘OK, well that’s not good.'”

Gosselin went from the game to Maine Medical Center in Portland. A normal heart rate for teenagers rests between 60 and 100 beats per minute. By the time Gosselin got to the hospital, hers was at 280, she said.

“It was definitely the heart racing, and I was just struggling to breathe,” she said. “They brought it down with methods like holding my breath, putting my legs up, putting ice on my head.”

SVT, according to Boston Children’s Hospital pediatric cardiologist Dr. Edward O’Leary, is an umbrella term for arrhythmias, and Gosselin’s subtype is atrioventricular nodal reentry tachycardia (AVNRT), the most common form among teenagers and adults. It affects around one in 1,000 people, O’Leary said, and is rarely life-threatening among those, like Gosselin, with otherwise healthy hearts.

“If they’re very infrequent episodes, if it happens once a year for two minutes, we generally say (to) keep on living your life,” O’Leary said. “When it starts interrupting school sports and (causes) frequent trips to the ER, we recommend treatment.”

Gosselin fell into the second group. Her heart rate spiked again during two travel softball practices and a basketball practice before the end of February, and doctors recommended she undergo a cardiac ablation, the most common procedure used to fix SVT. Ablation aims to correct the condition by triggering an arrhythmia, and then burning the problematic tissue with catheters inserted through the major blood vessels in the groin.

Gosselin had the three-hour procedure, performed by O’Leary, at Boston’s Children’s Hospital on April 1 – three days after Biddeford’s first practice of the season, and two weeks before the first game.

“Before the surgery, it was constantly on my mind, anywhere I went,” she said. “I was just stressed it was going to happen (again).”

Despite her worries, Gosselin tried to project a sense of calm.

“Throughout the winter, we were kind of going through that with her and it was really scary. Anything with the heart, you’re like ‘That’s never good,'” said junior pitcher Charlotte Donovan. “She kept on saying ‘Oh, it’s just a simple procedure.’ I was like ‘Oh, this is so scary.'”

Biddeford High second baseman Hannah Gosselin celebrates with teammates after scoring during a game against  Scarborough. Derek Davis/Staff Photographer

Following the surgery, Gosselin was out of action for 10 days. She started slow as she worked her way back, giving herself mini checkpoints to clear.

“I definitely had to do a couple of sprints to make sure I was fine,” she said. “Hitting, definitely, that jump out of the box was something I had to work on.”

Gosselin soon returned to the Biddeford lineup, playing a key role as the Tigers won their first eight games. And then on May 16, in the sixth inning of a game against Kennebunk, she felt the all-too-familiar symptoms. The chest pain. The racing heartbeat. The inability to catch a breath. And this time, a wave of dread.

Not again.

“I was nervous, because I just wanted the surgery to work and I was hoping everything went well,” she said. “I was very stressed.”

Gosselin tried to make it through the top of the seventh, but quickly found it was a losing battle. One of the best-fielding second basemen in the state, she made errors on two grounders, then had to summon trainer Stephanie Gabriner. She couldn’t continue.

“It was really tough. I couldn’t get it out of my head,” Gosselin said. “That last ball I went for, I was like ‘I can’t keep playing.’ It’s just panic, that I’m not going to be able to get (my heart rate) back down.”

Her teammates were concerned as Gosselin left the game.

“My heart just dropped,” Donovan said. “I was terrified.”

Watching from the dugout, Coach Mike Fecteau had a similar thought.

“It was scary,” he said. “You always think in the back of your mind, is it going to happen again?”

For all the concern, there’s good news. Gosselin’s heart rate after the game, O’Leary said, reached 160, which falls short of the levels of AVNRT. O’Leary said Gosselin going forward should be in the clear.

“The prognosis is good,” he said. “My hope is that this is over and done with for her.”

Hannah Gosselin stands with her parents, Keith and Tina Gosselin, and her grandfather Dennis Gosselin, left, on Senior Day for the Biddeford High softball team on May 31. Derek Davis/Staff Photographer

Gosselin makes sure she monitors her heart rate with both an Apple watch and a finger pulse oximeter.

“I feel much more confident now in my ability to stay out there,” she said. “It’s tough, but it’s something that I’m trying to keep as far in the back of my mind as possible, just because I don’t want that to mess up the way I play.”

The Tigers haven’t seen any caution out on the field.

“When she’s between the lines, she competes. It’s great to see,” Fecteau said. “She’s going to come here and play. She’s not thinking about what happened. She wants to win. It’s her senior year, these kids want to go out and get to the championship.”

During the regular season, Gosselin, a team captain, batted .442 in 15 games with 23 hits, 10 RBIs and 12 runs, and she’s helped lead Biddeford (13-2) to the No. 2 seed in the Class A South regional. The Tigers, who advanced to the state championship game last year, open the playoffs against Deering on Tuesday.

“She contributes a ton to the team,” said Bouchard. “And coming back from having heart surgery done, she’s progressed and she hasn’t let that slow her down at all. … She’s bouncing back, and it’s great to see.”

For Gosselin, who will be playing softball next year for St. Joseph’s College in Standish, the key is just staying calm. Stress mounts during a game, but Gosselin has found ways to keep herself centered.

“If I’m stressed or I make an error or get a bad hit, I come in (the dugout) and I calm myself down,” she said. “Or if I’m on the field, I just take a minute, take my glove off and I just breathe.”

The people around her help out as well.

“My dad (Keith) will come to me, and he’ll just be like ‘Breathe. Relax. You’re good,'” Gosselin said. “In all reality, it’s not a life-or-death situation. I just need to calm myself down so I can continue the rest of the game.”