Medical mystery: What caused healthy teen’s heart to stop?

In March 2018, Maeve Quinn was starting an exciting but stressful week of high school with both softball tryouts and play rehearsals.

But about 20 minutes into softball tryouts, the 16-year-old collapsed without any apparent cause.

First, her coaches and classmates thought it was a seizure. But then her trainer couldn't find a pulse: Maeve was in sudden cardiac arrest.

Maeve’s coach and trainer had a portable automated external defibrillator (AED) on hand and recognized the need to use it quickly. Within 90 seconds, Maeve’s coach shocked her heart and began administering CPR.

“It was a normal day, and then I got a call: ‘Maeve collapsed, she’s not breathing, they’re doing CPR. You have to get to the hospital.'” said Marguerite Quinn, Maeve’s mother. “I was driving to the hospital with my sons, praying she wouldn’t be dead when we got there.”

By the time EMTs arrived, Maeve had been without a pulse for 6½ minutes; her heart was not beating, and she wasn’t breathing on her own.

Without oxygen, her skin had started to turn blue.

EMTs administered two more shocks with the AED before they got a pulse and she began to breathe on her own again.

Maeve was taken first to a local hospital and then airlifted to Children’s Hospital of Philadelphia. She had poor muscle tone and low blood oxygen levels, and her lungs were filling up with fluid.

"I was worried about brain damage," Marguerite said.

What caused sudden cardiac arrest in this otherwise healthy teen?

Maeve woke up in the hospital the next morning with little memory of what had happened. While she focused on recovering, other clinicians and I in the cardiac center at Children’s Hospital of Philadelphia tried to figure out what caused her sudden cardiac arrest, as the condition is rare in young patients.

We credit the swift emergency action plan by her coach as critical to Maeve’s survival.

During the next 10 days, Maeve had approximately 100 tests — 40 on the first day alone.

She was tested for a structural defect in her heart. Doctors also looked at possible dysfunctions in her heart’s electrical rhythms, using a cardiac stress test and genetics testing. In addition, her family members underwent diagnostic screening to find potential clues, as many arrhythmic conditions are inherited. All of those tests came back with generally good results,

Because the tests did not yield a specific diagnosis, Maeve was diagnosed with idiopathic (unknown cause) ventricular fibrillation (IVF).

In adults, sudden cardiac arrest (SCA) and sudden cardiac death (SCD) usually are disastrous outcomes of diseases, especially coronary artery disease. But in young patients, they are mainly caused by genetic disorders of primary arrhythmic or structural origin or due to a viral infection of the heart called myocarditis.

IVF is a rare cause of SCA. Patients with IVF present with a sudden onset of ventricular fibrillation of unknown origin that is not identified even after extensive diagnostic testing.

The only treatment in patients with IVF is an implantable cardiac defibrillator (ICD) for protection against a recurrent life-threatening event. An ICD is a relatively small, battery-operated implanted device used to detect dangerously fast heartbeats and give a lifesaving shock to correct the heart’s rhythm.

There are two types of ICDs and both were medically appropriate for Maeve.

She opted for a subcutaneous ICD for two main reasons: It’s less invasive to the heart because the wire lead is attached to the outside of the organ, and the position of the device was less likely to interfere with her favorite sports: softball and volleyball.

Thirty hours after her implant surgery, Maeve was home for the first time in 11 days.

Less than a year after her sudden cardiac arrest, Maeve was cleared to start playing softball again. She has surprisingly few limitations on what she can do. "Basically, the only thing I can’t do is the rope climb in gym class and no contact sports," Maeve said. However, as she recovers and heals, doctors hope that she will be able to return to full activity.

She's also had to adjust to some minor side effects from the beta blocker medication she takes to help regulate her heart rhythms. At times, she feels overheated or faint.

There are a few other changes. Maeve’s genetics tests were inconclusive, but both her brothers had unusual results on their cardiac stress tests and now take beta blockers, too. We will continue to monitor Maeve and her family and look for ongoing clues.

And the family has a portable AED now — just in case her brothers or other family members have a cardiac arrest.

Maully J. Shah, MBBS, is an attending pediatric cardiac electrophysiologist in the Cardiac Center at Children’s Hospital of Philadelphia.