Problems with the speed or rhythm of the heartbeat are caused by disorders in the heart's electrical system. Atrial fibrillation (AF) is the most common type and can lead to an increased risk of stroke. Symptoms of AF include an abnormally rapid heartbeat, shortness of breath, difficulty exercising, chest pain, dizziness, and confusion. The CYP11B2 gene provides instructions for making an enzyme called aldosterone synthase. This enzyme is found in the adrenal glands and is a member of the cytochrome P450 family of enzymes. Aldosterone synthase helps produce a hormone called aldosterone. Aldosterone helps control blood pressure by maintaining proper salt and fluid levels in the body. A meta-analysis including 2,758 subjects from six individual studies showed that a polymorphism in the CYP11B2 T-344C gene was associated with AF risk.