Heart palpitations caused by an eating disorder? A teen’s medical mystery reveals the dangers of weight talk.

A 15-year-old came to the emergency department with heart palpitations, and hospital staff weren’t sure what was wrong.

Aside from some muscle cramps he attributed to an intense workout, his day had started like any other: He filled a travel mug with coffee and sprinted out of the house to catch the school bus.

Then, during a particularly difficult math test, he suddenly felt his heart skipping a beat and thought he might pass out. He went to see the nurse, who found his pulse was extremely low. She called a parent to take him to the hospital.

A triage nurse at the hospital rushed him back to the treatment room because he looked so pale and ill. His vital signs showed a heart rate (pulse) of 30 beats per minute — well below the normal range for teenagers of 55-85 beats per minute. Doctors ordered an electrocardiogram (EKG) and blood tests.

Heart palpitations include the feelings of the heart skipping a beat, racing, or pounding. One of the first things we think of with teens who complain of palpitations is anxiety. Our patient’s symptoms sounded like a classic panic attack — the sudden onset of intense physical symptoms including heart palpitations and light-headedness, with a sense of impending doom. A panic attack, however, would cause a fast pulse (tachycardia), not a slow pulse (bradycardia).

Consuming too much caffeine can also cause heart palpitations. Caffeine is in many of the things we know and love including coffee, tea, soda, and even chocolate. Teens should consume no more than 100 mg of caffeine daily, the average amount in one cup of coffee. Our patient drank only one cup of coffee. But caffeine also causes a fast heart rate, while our patient’s heart rate was slow.

Anemia is another cause of teen heart palpitations. Anemia occurs when the number of red blood cells that carry oxygen to the body is low. Symptoms include pale skin, feeling light-headed, and heart palpitations. Four months earlier, our patient decided to become vegan. Vegans are at risk for anemia caused by iron-deficiency or B12 deficiency because they don’t eat meat or animal products, such as dairy and eggs, that are rich in those nutrients. Still, our patient’s blood tests came back normal, so anemia was not the cause of his heart palpitations.

Not anxiety, not over-caffeinating, and not anemia. What’s going on?

Clue No. 1: Our patient’s blood work showed a low potassium level, which is called hypokalemia. Potassium is found in foods like bananas, fruits, and vegetables. Low potassium can be caused by vomiting, diarrhea, kidney disease, and medications. Low potassium can cause bradycardia and muscle cramps. Now we were getting somewhere.

Clue No. 2: Our patient’s growth curve showed his weight was above average for his age and height, but that he’d lost 50 pounds rapidly over the past four months. His growth curve looked like a dangerous cliff. He told us that for as long as he could remember, his primary care provider had told him he was overweight and needed to exercise and eat healthier. He always hated the way he looked — he wanted to change “everything,” he told us.

Four months earlier, after his annual checkup, he decided to do something about it. He became vegan. He exercised for three hours every day. He skipped breakfast and lunch, except for coffee. After school, he was ravenous and consumed large amounts of food. Then, frantic about possible weight gain, he forced himself to vomit. He repeated this vicious cycle of bingeing and purging daily.

When he started to lose weight, people told him how great he looked, so he kept losing and losing. Our patient had an undiagnosed eating disorder.

Our patient had recently learned about a new social media fad called “water flushing,” which is drinking five water bottles and purging after each, to get rid of all stomach contents. Medical care providers would never recommend water flushing for any reason as it is extremely dangerous.

Our patient confided in us that the night before, he had tried water flushing for the first time.

He was hospitalized for heart monitoring while correcting his potassium level. Next, he needed to start treatment for atypical anorexia nervosa with bingeing and purging. It is called “atypical” because he was of normal weight, despite weight loss. His treatment team would require a medical care provider, dietitian, and eating disorder therapist.

» READ MORE: Preventing eating disorders starts at home. Here’s how to promote healthy habits for your teen.

Our advice:

Rachel Knapp is a pediatric resident and Rima Himelstein is an adolescent medicine specialist at Nemours Children’s Hospital in Delaware.