ECG Review: The QRS Complex in Lead V2

By Ken Grauer, MD

Figure. 12-lead ECG obtained from a 73-year-old man with dyspnea.

Clinical Scenario: The electrocardiogram (ECG) in the Figure was obtained from a 73-year-old man with documented coronary disease and heart failure. He now presents with a 10-day history of dyspnea. How would you interpret his ECG? How does the appearance of the QRS complex in lead V2 contribute to your answer?

Interpretation: The rhythm is slightly irregular. Although the amplitude of P waves in the limb leads is greatly reduced, the rhythm is probably sinus (suggested by regularly occurring atrial activity in leads V1, V2, V3). The QRS complex is widened. The pattern is most consistent with complete right bundle-branch block (RBBB) in view of the widened tall R wave in lead V1 that occurs in association with wide terminal S waves in lateral leads I and V6. The atypical feature of this RBBB pattern is the absence of an initial small r wave in lead V1 (a QR pattern is seen, instead of a more typical rSR’ pattern). Because a small (but definite) q wave is seen in lead V2, one should strongly suspect septal infarction as the cause of the initial Q wave in those two precordial leads. Further support of our suspicion that the patient has had an anterolateral infarction is supported by the presence of primary ST-T wave changes in each of the three key leads. Normally the direction of the ST segment and T wave in typical right or left bundle-branch block is opposite the direction of the last QRS deflection in each of the three key leads (leads I, V1, and V6). Thus, the T wave normally will be upright in both leads I and V6 (opposite the wide terminal S wave in those leads), and the ST segment and T wave are likely to be negative in lead V1 (opposite the positive R or R’ complex). The contrary is true in this case; note especially the hint of ST-segment elevation in lead V1. In addition, deep symmetric T-wave inversion is seen in leads II, aVL, aVF, and V3 through V6 of this tracing. The overall ECG picture, in conjunction with the history of heart failure in this 73-year-old man strongly suggest the possibility of recent ischemia and/or infarction superimposed on the underlying pattern of RBBB. Perhaps an event (e.g., a myocardial infarction) and/or ongoing ischemia precipitated this patient’s most recent episode of dyspnea?

Dr. Grauer, Professor and Associate Director, Family Practice Residency Program, Department of Community Health and Family Medicine, College of Medicine, University of Florida, Gainesville, is on the Editorial Board of Emergency Medicine Alert.