Use of vectorcardiography in determination of the left ventricular muscle mass.

Many studies have investigated different ECG and vectorcardiographic (VCG): criteria for diagnosis of left ventricular hypertrophy (LVH). In some investigations VCG was more sensitive than ECG in this respect. This study was performed to elucidate whether it is possible also to determine the degree of LVH using VCG. Eighty cardiovascularly healthy subjects aged 15-39 were investigated with ECG, VCG (Frank system) and echocardiography. The echocardiographic left ventricular (LV) mass has been shown by others to correlate closely to the anatomical and the angiographically determined LV mass and was used as reference standard. Thirty-eight of the subjects were endurance sportsmen and had a LV mass above standard reference limits. The measured ECG variables were R-amplitude in a VL, I, V5, V6, S-amplitude in V1 and SV1 + RV5/V6 and the VCG variables were QRS spatial area and circumference and left maximal spatial vector. The sensitivity and specificity of single criteria tested were similar for ECG and VCG in the quantitative determination of LVH. The correlations between ECG-amplitudes and the magnitude of the LV mass were weak. The correlations were higher with the VCG-variables, QRS spatial circumference being superior to the others, but not good enough to permit an estimation of the LV mass in individual subjects. In conclusion, normal VCG variables were highly specific for a normal LV mass but in individuals with LVH, VCG was not useful for the estimation of the LV mass.