Quantitative VCG analysis in old myocardial infarction diagnosis

Abstract

'Quantitative' VCG method for diagnosis of old myocardial infarction have been evaluated with a pilot study, in 90 patients: 45 with old myocardial infarction (Group-A), and 45 control group (Group-B). Patients with 'non Q' infarction were included. A reduction of the values of these parameters: ΣA (sum of the areas projected on the three orthogonal planes (XYZ) by the spatial QRS loop), Σ1/2A (sum of the half-areas), ΣMV (sum of the maximum vectors of the QRS on the three orthogonal planes), ΣMV1/2A (sum of the vectors of the half-areas), witch show 'total' electrical activity, were considered as possible markers of myocardial necrosis. Difference between the two groups were tested for statistical significance using Student's t-test. Sensitivity and specificy of this method were also evalueted. A significantly difference in the parameters considered, was found between the two groups. - ΣA: Group-A (mean 0.98±0.1 cm2); Group-B (mean 1.81 ± 0.13 cm2); t = 4.6349; p<0.05. - ΣMV: Group-A 27.8±1.7 mm; Group- B 37.42±1.3 mm; t = 4.5073; p<0.05. - Σ1/2A: Group-A (mean 0.49±0.05 cm2); Group-B (mean 0.91±0.07 cm2); t = 4.4163; p<0.05. - ΣMV1/2A: Group- A 21.1±1.9 mm; Group-B 30.3 ± 1.9 mm; t = 4.4163; p<0.05. The patients with non-Q myocardial infarction (8 patients) did not show any difference in all parameters in respect of the others of Group-A. The greatest specificity of the test (80%) was obtained assigning a threshold value of >0.91 cm2 to the ΣA parameter. The greatest sensitivity of the test (62.2%) was obtained assigning a threshold value of <33 mm to the ΣMV1/2A parameter. Using the two parameters simultaneously, a teat efficiency of 71.1% was obtained. Using the VCG method described, it has been possible to identify a significant reduction in the 'total' electrical activity of the heart in patients with old myocardial infarction, as compared to the controls. Diagnosis was also possible in the patients with non Q myocardial infarction, since the parameters used are quantitative and do not depend by the presence of morphological modifications of the QRS complex, should be useful employed in patients with myocardial infarction and LBBB or ventricular preeccitation.