Vectorcardiographic evaluation of myocardial infarct size: comparisons with thallium myocardial scintigraphy

OBJECTIVE: To determine the usefulness of vectorcardiography (VCG) in assessing myocardial infarct size. METHODS: The correlation of spatial and scalar parameters of VCG with the percent defect volume (%DV) of thallium myocardial single photon emission computed tomography (SPECT) was investigated in 63 patients with first-onset myocardial infarction (MI). VCG parameters included: (1) spatial parameters: magnitude, azimuth and elevation of the maximal vector, vectors at 20 ms and 30 ms, and (2) scalar parameters: amplitudes of 20 ms and 30 ms vectors at X, Y, and Z scalar leads abbreviated as X20, Y20, Z20, X30, Y30 and Z30, respectively. RESULTS: For anteroseptal MI, the azimuth of 30 ms vector and Z20 showed a significant correlation with %DV (r = 0.572, P < 0.05 and r = 0.832, P < 0.001) while in anteroseptal MI with involvement of lateral wall, the azimuth of 30 ms vector and X30 were correlated with %DV significantly (r = 0.775, and r = 0.780, P < 0.01). For inferior and inferoposterior MI, the elevation of 30 ms vector and Y30 were correlated well with %DV (r = 0.871, P < 0.01, r = 0.928, P < 0.001 for inferior MI and r = 0.678, P < 0.01, r = 0.760, P < 0.001 for inferoposterior MI). CONCLUSION: VCG parameters, especially scalar parameters, can be used to evaluate myocardial infarct size easily and non-invasively with remarkable accuracy.