Abstract:Objective The electrocardiogram and vectorcardiogram were synchronously collected by stereo electrocardiograph using Wilson and Frank dual-lead system to timely detect and diagnose left anterior branch block. MethodsThe case of left anterior branch block with clinical manifestations and welldefined by vectorcardiogram were selected. Results Vectorcardiogram of 4 patients with left anterior branch block showed that the starting vector of frontal QRS ring was located at the lower right or left side, while the maximum vector shifted to the upper left. The main feature of the ring is that it ran counterclockwise and expanded to the upper left quadrant. Conclusion Vectorcardiogram is superior to electrocardiogram in the diagnosis of left anterior branch block. In the practical work, we should adopt the principle of complementary advantages of ECG and vectorcardiogram to well serve the clinic. The combination of the two methods can improve the accuracy of diagnosis.