What is atrial fibrillation and how is it treated?

NEW YORK — Daniel Moore was about 30 the first time it happened. At the end of a long, hot, stressful day, he chugged an ice-cold glass of milk.

''It felt like a bunny rabbit trying to jump out of my chest," said Moore, now 60.

Moore, a radiologist, knew what it was: A-fib.

Short for atrial fibrillation, A-fib is a quivering or irregular heartbeat that is a worrisome stage-setter for blood clots, stroke and heart failure. Some researchers believe more than 10 million Americans have it — most of them older. And it's expected to become even more common in the years ahead.

Yet, University of Utah heart researcher Dr. T. Jared Bunch sees reason for optimism.

"Even though we see more of the disease, we're better at treating it,'' said Bunch, who co-authored a book on A-fib.

Symptoms can include shortness of breath

''I definitely have no exercise tolerance when I'm in it,'' Moore said. ''I can't run. Walking is tiring faster. I get a little light-headed standing up.''

The heart can surpass 200 beats per minute for someone with A-fib, more than double the 60 to 100 beats typical for a healthy adult's resting heart rate.

Symptoms can come and go, and it's not usually life-threatening by itself. But the erratic beating can lead to blood pooling in the heart that can become clots in days or even hours. Those clots, in turn, can travel to the brain and cause strokes.

A-fib also can increase the risk of developing ventricular fibrillation — a more serious condition.

Diagnosis is becoming more common

Many people who experience symptoms don't understand what is happening.

The American Heart Association found that more than half of people with A-fib didn't know about the condition before they were diagnosed.

Studies have suggested 15% or more of strokes can be tied to A-fib, and that the percentage rises in older people. The condition is one reason that U.S. stroke deaths rose in the last decade, although the stroke death rate has dipped in the last few years.

What causes A-fib?

Researchers attribute A-fib to damage in the heart's upper chambers and its electrical signaling. Genetics can play a role, but other contributors include high blood pressure, diabetes, stress, sleep apnea, smoking and alcohol.

Viruses can also pose a threat because they can affect the proteins behind the heart's electrical signals or prompt an immune response that damages heart tissue. COVID-19 is among the list of viral culprits, and likely contributed to A-fib in some patients, experts say.

Studies have found no link to COVID-19 shots, said Dr. Jose Joglar, a Dallas-based expert who helped author American Heart Association guidelines on A-fib diagnosis and management.

Doctors have a range of treatment options

There's no cure, but a number of therapies can help manage the problem.

''We're miles beyond where we used to be'' in treating A-fib, said Dr. Laurence Epstein, of Hofstra University and Northwell Health. ''The technology has really evolved.''

For some patients, doctors may recommend implanted devices. Pacemakers can regulate heart rhythm, and a device called a Watchman can close off a clot-prone area of the upper heart.

And then there's ablation. It's a procedure in which a doctor uses heat, cold or electric pulses to zap certain areas of the heart, creating scars that block faulty electric signals. Traditionally, ablation was used when other approaches failed, but in recent years ablation techniques have become more advanced and it has become a first choice for certain patients, including those with heart failure.

Medications to regulate the heart or thin the blood to reduce stroke risk can have problematic side effects.

How to lower your risk

People can lower their risk of developing A-fib by living a healthy lifestyle. That includes exercising, getting enough sleep, eating a healthy diet, managing high blood pressure, and avoiding tobacco products and alcohol.

If symptoms do develop, it's important to take them seriously, said Amy Stahley, who was first diagnosed three years ago.

She went to bed one night and her heart began racing to more than 150 beats per minute. She immediately went to a hospital.

''If you're feeling a little off, get it checked out,'' said Stahley, who is a nurse and dean of Davenport University's College of Health Professions in Michigan.

Moore, a radiology professor at UT Southwestern Medical Center in Dallas, agreed.

''The longer you stay in A-fib, the more likely you are to stay in it for life,'' he said.