Hypertrophic cardiomyopathy with asymmetric septal hypertrophy is one of the diagnoses that should be considered when abnormal Q waves suggestive of an infarction are encountered in younger patients. A second cause of Q waves simulating an infarction in younger patients is ventricular pre-excitation (WPW). Recall from chapter 3, the chapter dealing with intraventricular conduction disturbances, that pre-excitation of the ventricles by an AV nodal bypass tract, shown here in yellow, causes a short PR interval and an abnormal initial portion of the QRS complex that is referred to as a delta wave. The location of the bypass tract will determine whether, and in what leads, the delta wave will be positive or negative. In the example shown here, the bypass tract is on the right lateral wall and is responsible for the delta wave that is positive (or upright) in lead V5.