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 4=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.