Can U waves be "notched"?

Abnormal U waves (unduly larger or misshapen) are associated with several conditions such as hypokalemia, arrhythmias, cardiac ischemia, ventricular hypertrophy, and hypertension. Abnormal U waves have also been linked to certain cardiac medications, predominantly antiarrhythmics. However, mechanisms of U-wave-abnormality remains debated and perhaps elusive with the true U-wave relationship to T waves still being investigated. While there have indeed been reports of bifid ("notched") T waves, such comparably described U waves have escaped us thus far. We present a case of possibly bifid U waves that persisted over the course of 10 years in the setting of repeated negative Holter monitor findings and clinical absence of atrial tachyarrhythmias. We take this opportunity to briefly discuss common causes of "normal" and abnormal U waves.