The Relationship between Spatial Velocity and Magnitude Electrocardiograms

By using an analogue computer with the X, Y and Z components of Frank's lead system as inputs, spatial velocity electrocardiograms (SVECG, SV), and spatial magnitude electrocardiograms (SMECG, SM) were recorded. At the same time, utilizing a direct writing vectorcardiograph and a X-Y plotter, a correlation curve between SVECG and SMECG was traced. Thirty normal human subjects, 21 patients suffering from hypertension without cardiac involvement and 70 cases of ischemic heart disease (IHD), such as myocardial infarction, angina pectoris, and asymptomatic IHD were studied in a recumbent position before and after Mster's two-step test. The SMECG of QRS of the hypertensive patients was significantly greater both before and after exericise than that of the normal group, while that of the IHD group showed a significance only after the exercise. If the peaks of QRS and T of SVECG are called ρ1, ρ2, τ1, and τ2in their respective order, the ρ2 after exercise, τ1 before and after ex-ercise, and τ2 before exercise are significantly elevated in the hypertensive patients. τ2 showed a significant increase after exercise in each group studied, while τ2 in the normal and hypertensive groups declined noticeably. SV and SM showed good positive correlation, but the correlation coefficient was poor in the IHD group and worsened after exercise. In the IHD patients, the positive group of the two-step test showed significantly poorer correlation than the negative group at ρ1. This indicates that SV is not determined by SM alone.