The Normal Ventricular Gradient Determined with Frank's Lead System and Its Relation to the Heart Rate Change Induced by Various Procedures

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Abstract
The ventricular gradient (G) vector was determined with Frank''s lead system in 60 normal subjects. In some cases, the effect of eyeball or carotid sinus pressure, atropine sulfate, upright position and amyl nitrite was examined. The average magnitude of the G vector was 80.3 uv.sec and its average direction was 44[degree] and 27[degree] in the frontal and horizontal plane, respectively. In acute experiments with various agents, the magnitude of the G vector increased or decreased along with the RR interval. The directional change of the G vector relative to the QRS vector was small. The importance of the G vector in analysing the acute electrocardiographic changes, especially in the horizontal plane, was discussed. The change in the G magnitude relative to the R-R or Q-T change was larger in the experiments with standing position and amyl nitrite than in the other 2 experiments, which might be related to the difference between the heart rate changes of sympathetic and parasympathetic origin.