QS- and QR-Pattern in Leads V 3 and V 4 in Absence of Myocardial Infarction: Electrocardiographic and Vectorcardiographic Study

Abstract

A QS or QR pattern in the absence of myocardial infarction is frequently present in lead V₃ and occasionally in lead V₄. Exploration by means of multiple chest and abdominal unipolar leads and vectorcardiograms revealed that in almost all such cases, the vector of the initial portions of the QRS complex is directed downwards. Accordingly, in the absence of infarction, patients presenting this pattern almost invariably showed an initial R wave in the leads recorded from positions below the standard level of V₃ and V₄. The vast majority of patients with myocardial infarction with a similar QRS pattern showed a Q wave in the lower leads. Consideration of vertical components of cardiac voltages may be helpful in the interpretation of the precordial leads.