The Timed Vectorcardiogram: A Useful Clinical Tool

(As Applied to the Study of 1,500 Subjects)

¹ Assistant Professor of Medicine and Associate Director, Cardiopulmonary Laboratory, Loma Linda University; work initiated under Cardiology Fellowship, National Institutes of Health
² Assistant Professor of Medicine, Loma Linda University; work done during tenure of fellowship from National Medical Fellowships, Inc.
³ Clinical Professor of Medicine and Coordinator, Cardiovascular Teaching, Loma Linda University

1. The data from 1,500 normal and abnormal subjects have been surveyed in which the vectorcardiographic loops are recorded along a continuous axis, producing a timed vectorcardiogram.

2. Time relationships (rate, rhythm, PR interval, QRS interval, QT interval, etc.) were routinely recorded and readily measured in all timed vectorcardiograms.

3. P Vectors — Two separate components to the P vector, an early (right atrial) component and a late (left atrial) component were recorded in every subject with a sinus rhythm. These are more easily seen in the timed vectorcardiogram than in the spatial vectorcardiogram and not usually seen in the electrocardiogram.

4. QRS Vectors — At least three separate components to the QRS forces were identified in both the normals and abnormals with normal intraventricular conduction, and their mean values both as to magnitude and spatial orientation were recorded. They are (1) Early septal forces (initial 0.015 second), (2) Mid septal plus apical forces (0.0 15 to 0.040 second vectors), and (3) Late septal plus main ventricular depolarization (terminal 0.040 second vectors). The timed tracing produced no significant distortion of these vectors.

5. The ST and T Vectors were usually well seen in the timed vectorcardiograms. In 5 per cent of cases, however, these vectors were slowly written and small enough so as to be obscured by the addition of time to the transverse axis of all three planes. This was not a problem if the spatial vectorcardiogram which was done at the same time was reviewed in conjunction with the timed tracings.

6. QRS-T Angles — The good correlation previously reported between the timed vectorcardiogram and electrocardiogram as far as the mean QRS, mean T, and QRS-T angles are concerned when the Burger Triangle is used as a reference frame in the frontal plane, and the Grant and Estes reference system is used for precordial leads, was further confirmed.

7. It would thus seem that a frontal plane timed vectorcardiogram records in a single tracing information equivalent to that of the six limb leads of a conventional electrocardiogram. The horizontal plane timed vectorcardiogram recorded the information available from six or more precordial leads of the conventional electrocardiogram. The sagittal plane tracing records this same information in a third plane.

8. It is concluded that the timed vectorcardiogram appears to combine the advantages of the time relationships as best shown in the electrocardiogram, and the graphic portrayal of vector forces as best seen in the spatial vectorcardiogram into a single simplified graphic method.