A standard reference system for spatial vectorcardiography. Comparison of the equilateral tetrahedron and the Frank systems

The sVCG was recorded with both the equilateral tetrahedral and Frank reference systems and carefully studied in 450 patients and normal subjects, the hearts of 30 of these patients being studied carefully at autopsy. Ninety of the patients were geriatric, and all of the other patients had organic heart disease. The sVCG recorded with the two systems were remarkably similar in most instances. However, in many patients with heart disease the tetrahedron produced recordings which were more abnormal than those produced with the Frank system. In only one of the group of sVCG studied with wire models did the Frank system provide more clinical assistance than the tetrahedron, but the tetrahedron was more helpful clinically in detecting cardiac disease in many instances. The latter was especially true in the geriatric patients whose electrocardiograms appeared to be even normal in some instances. The study of these 450 people indicates that for practical clinical purposes the equilateral tetrahedral reference system is definitely superior to the Frank system. The technicians found the tetrahedron to be easier to employ. The back electrode was the only other electrode needed when recording the sVCG with the ECG. This back electrode was easy to place reliably and reproducibly. The Frank system was difficult and at times impossible to employ accurately in newborn infants, obese patients with small or large hearts, patients with deformed chests, very ill people, and in postoperative patients with dressings on the chest. The sVCG recorded with the equilateral tetrahedral system in general revealed abnormalities of the heart earlier and with greater disturbance in contour, direction of rotation, and spatial orientation than the sVCG recorded with the Frank system. The Frank system tended to make the contour of the complexes smooth, thus erasing early and definite irregularities and distortions in configuration which were often related to myocardial disease. We strongly advise the use of the equilateral tetrahedron as the standard system for clinical vectorcardiography the world over. Until a simple, easy, reliable, and reproducible reference system such as the equilateral tetrahedron is accepted for general clinical use, vectorcardiography is unlikely to become a useful routine procedure in clinical practice in hospitals, clinics, and physicians' offices.