Atrial fibrillation, known as AFib, is the most common heart rhythm disorder in the United States and can significantly increase the risk of stroke and heart failure, according to a local specialist.Dr. James Berrios, a cardiologist with Our Lady of the Lake Health, said AFib occurs when the heart’s upper chambers beat irregularly and inefficiently. The condition affects millions of Americans and becomes more common with age.Symptoms may include heart palpitations, shortness of breath, fatigue and dizziness, though some patients have no symptoms. Dr. Berrios said early diagnosis, stroke prevention and routine medical care are critical to protecting long term heart health.