The Vectorcardiographic Diagnosis of Myocardial Infarction

¹ The Department of Medicine, Harvard Medical School, and the Electrocardiographic Laboratory, Beth Israel Hospital, Boston.

1. The initial, early, and terminal forces associated with ventricular depolarization can be studied in greater detail and more accurately by spatial vectorcardiography than by electrocardiography.

2. The initial, early, and terminal forces are stereotyped in the normal heart, right and left ventricular hypertrophy, and right and left bundle branch block, and are altered in a characteristic way by changes in heart position and rotation. The initial and/or terminal forces help in establishing the position and degree of rotation of the heart.

3. Changes in the initial forces which cannot be explained on the basis of heart position and rotation are diagnostic of septal disease.

4. Changes in the early forces indicate infarction of the free wall of the left ventricle. Localization of infarction is established in reference to the three natural coordinate axes of the body. The abnormal vectors are oriented posteriorly and down in anterior infarction, anteriorly and down in high posterior infarction, up and posteriorly in infero-posterior wall lesions, to the left in lesions close to the interventricular septum, and to the right in lateral wall involvement. Reversal in the direction of inscription of the vectorcardiographic projections frequently results from displacement of the forces, and furnishes valuable additional help in the diagnosis of infarction. Clockwise inscription of the posteriorly placed horizontal projection is diagnostic of anterior infarction, and clockwise inscription of the horizontally placed frontal loop is diagnostic of posterior wall infarction.

5. The QRS loop is open in acute infarction, and the position of the end to the beginning of the loop is characteristic in anterior infarction, posterior infarction, acute pericarditis, and right and left ventricular hypertrophy. The T loop is long and narrow in acute, and small and round in healing or old myocardial infarction.

6. Comparison of vectorcardiographic and electrocardiographic Interpretation in 50 cases studied at autopsy indicates unqualified superiority of the vectorcardiogram in the diagnosis of myocardial infarction, and right and left ventricular hypertrophy, singly or combined. The vectorcardiogram is superior for localization, and for detecting multiple areas of infarction. This superiority is evident in relation to anterior, posterior, and septal infarction. False vectorcardiographic diagnosis of infarction did not occur in this series.

7. Spatial vectorcardiography is a useful method of examination and its use should be extended.