Identification of susceptibility to ventricular tachycardia after myocardial infarction by nondipolarity of QRST area maps

Division of Cardiology, Showa University Fujigaoka Hospital, Yokohama, Japan.

The QRST area map has been related to susceptibility to ventricular tachyarrhythmias because it reflects the disparity of ventricular recovery properties. However, the clinical value of the nondipolarity of the QRST area map, a marker of nonuniform ventricular repolarization, has not been fully studied in myocardial infarction. The nondipolarity of the QRST area map (residue), the ratio of minimized deviation by an optimal dipole to the total measured potentials, was quantitatively studied in relation to susceptibility to ventricular tachycardia after myocardial infarction. The residue of the QRST area map was higher in 59 patients with myocardial infarction than in 44 normal subjects (25.0 +/- 9.0 versus 17.8 +/- 3.3%, p less than 0.01). Seventeen patients with ventricular tachycardia in the chronic phase (greater than 10 days) of myocardial infarction showed higher residue in their QRST area map (34.5 +/- 10.3%) than that in 29 patients without ventricular tachycardia throughout the study (22.7 +/- 6.7%) or that in 13 patients with ventricular tachycardia only in the acute phase (21.2 +/- 7.5%). QRST area maps with a residue greater than or equal to 25% (mean + 2 SD of normal subjects) identified patients with ventricular tachycardia in the chronic phase of myocardial infarction with a sensitivity of 82% and a specificity of 71%. These results suggest that quantitative assessment of the nondipolarity of the QRST area map is clinically useful for identifying susceptibility to ventricular tachycardia in the chronic phase of myocardial infarction.

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