Vectorcardiographic Analysis of Left Axis Deviation, in the Differentiation of Diaphragmatic Infarction and Parietal Block

¹ Director, Vectorcardiographic Laboratory—Division of Medicine, The Mount Sinai Hospital of Cleveland
² The Division of Medicine, Vectorcardiographic Laboratory and Eva and Irving Hexter Cardio-Pulmonary Laboratory, The Mount Sinai Hospital of Cleveland

1. Vectorcardiographic analysis of abnormal left axis deviation (mean electrical axis between 270°-330° in the frontal plane of the scalar electrocardiogram) has shown that this condition results from an abnormal pathway of depolarization.

The two most common entities responsible for this condition are parietal block and diaphragmatic infarction.

2. An rS complex in aVF may be found in a significant proportion of diaphragmatic infarctions and when associated with abnormal left axis deviation, may superficially resemble parietal block on the scalar electrocardiogram.

The major feature differentiating these two abnormalities has been shown to be the direction of inscription of the QRS sE-loop in the frontal plane. Parietal block is characterized by counterclockwise inscription, whereas diaphragmatic infarction always produces clockwise inscription of some portion of the QRS sE-loop.

3. We believe that the initial r wave in aVF in the presence of diaphragmatic infarction results from inferiorly directed septal forces in most instances. An rS complex in aVF in cases of parietal block, on the other hand, is probably dependent upon early depolarization of the inferior wall. Septal fibrosis and infarction complicating parietal block requires vectorcardiographic display for correct interpretation.