Left isomerism in a middle-aged woman with early-onset atrial fibrillation.

An unusual case of left isomerism in a 52-year-old woman with early-onset atrial fibrillation was presented. Magnetic resonance imaging clearly delineated the morphology of both atrial appendages, the vascular anatomy and all other associated anomalies, obviating further invasive studies. The discovery of left isomerism at advanced age indicates that abnormal atrial situs itself is of less clinical importance, and despite the associated sinus node dysfunction may predispose the heart to atrial fibrillation.