The residue value on dipole analysis (the ratio of nondipolar component to the measured body surface potentials) was estimated mathematically in 16 patients with left bundle branch block. Patients ...were classified into those with (group A, nine patients) and those without (group B, seven patients) a perfusion defect on thallium-201 myocardial scintigraphy. For the entire QRS complex the residue of group B was smaller than that of normal subjects (20.0 ± 4.1% versus 24.6 ± 3.5%, p < 0.05). Group A showed a greater mean residue value than group B (27.4 ± 4.4% versus 20.3 ± 2.4%, p < 0.01) only during the initial one-third of the QRS complex. All but one patient of group A and only one patient in group B showed a high peak on the residue curve during the initial stage of the QRS complex. The maximal residue value of group A during the initial QRS complex was significantly greater than that of group B (40.9 ± 10.9% versus 23.4 ± 5.4%, p < 0.01). An arbitrarily selected criterion of the maximal residue value ≥30% during the initial QRS complex showed a sensitivity of 89% with a specificity of 86% for the diagnosis of myocardial infarction in the presence of left bundle branch block.
These results might be related to the complex ventricular activation around the infarcted area even in the presence of left bundle branch block in which intramyocardial conduction with a simple activation front predominates. Dipole analysis appeared to be a valuable method of diagnosing myocardial infarction in the presence of left bundle branch block.
The dipolarity of the body surface potential distribution and locus of the main dipole were estimated by means of the least square method in data base for body surface potential maps of normal ...population. The main dipole moved smoothly within the actual cardiac region and was inscribed in a clockwise direction during the QRS. The nondipolar content (residue) showed time-dependent fluctuation the QRS. The main dipole during the T wave moved near the center of the heart. The nondipolar content during the ST-T period was less fluctuation than that during the QRS. These results indicated that a large percentage of the body surface potential maps of normal population could be represented by a single moving dipole.
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 < 0.01). Seventeen patients with ventricular tachycardia in the chronic phase (>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 ⩾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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