Atrial fibrillation may occur without evidence of underlying heart disease. This is more common in younger people, about half of whom have no other heart problems. This is often called lone atrial fibrillation. Some of the causes that do not involve the heart include the following:
- Hyperthyroidism (overactive thyroid)
- Alcohol use (holiday heart or Saturday night heart; a condition of A fib, supraventricular tachycardia, or other cardiac arrhythmia usually triggered by some holiday-related event such as increased alcohol drinking or discontinuing medications; the condition often subsides once the triggering behavior is ceased)
- Pulmonary embolism (a blood clot in the lungs)
- Pneumonia
