This electrocardiogram shows left ventricular hypertrophy and left anterior fascicular block. The characteristic features of left ventricular hypertrophy demonstrated here include increased voltage, reflected by the tall R wave in aVL exceeding 11 mm, ST-T abnormalities well seen in this lead as well as leads I, aVL, V5 and V6, a prolongation of the QRS interval , and left atrial enlargement, reflected by the wide P wave in lead II and the prominent negative P wave in lead V1. Left anterior fascicular block is manifested by left axis deviation of ≥ -45° and is reflected by the negative QRS in lead II with an rS morphology in lead II.

One common axis criterion is a deviation of ≥ -45°, as evidenced here by the negative QRS complex in lead II. Because of the marked left axis deviation, there is often delay in R wave progression across the precordium, as seen here.

Left anterior fascicular block may be seen in otherwise normal patients. When seen in association with electrocardiographic changes of anteroseptal ischemia and/or infarction, it likely represents left anterior descending coronary artery disease.