[Relationship between the occurrence of late potential and the location and size of myocardial infarction evaluated by thallium-201 SPECT].
High-frequency, low amplitude signals, late potentials (LPs), in the terminal portion of the body surface QRS of the signal-averaged ECG were frequently observed in ventricular tachycardia (VT) following myocardial infarction (MI). In this study, we evaluated the correlation between the occurrence of LPs and the size and location of MI estimated by Thallium-201 myocardial SPECT in 30 MI patients. The positive LPs were identified by the value of %RMS 40, the percent ratio of the root mean square voltage in the last 40 msec of the QRS complex to that of the total filtered QRS from the signal averaged ECG using bipolar X, Y, Z leads. The spatial distributions of LPs were evaluated by the LP30 area maps obtained by the body surface mapping using forty-five unipolar electrodes. Sixty projections were obtained over 180 degree by rotating gamma camera after 5 minutes intravenous injection of 74 MBq of Thallium-201. After low-pass filtering, images were reconstructed into short-axis, horizontal long-axis and vertical long-axis tomograms. The maximum count circumferential profiles for each short-axis cuts were generated from the apical to basal cut and they were expressed into two-dimensional polar functional maps (apex to the center), Bull's-eye map, to represent myocardial Tl distribution. Normal limits of myocardial Tl distribution were established as the mean minus 2 standard deviation from those of normal subjects. The MI size was estimated as defect volume ratio (DVR), the percent ratio of abnormal region to that of total volume of left ventricle. Significant differences in DVR were observed among MI with LPs and without LPs.(ABSTRACT TRUNCATED AT 250 WORDS)
Nakai
K
K
Department of Clinical Pathology, Iwate Medical University, Japan.
Ito
C
C
Moriai
N
N
Miyakawa
T
T
Aoki
H
H
Suzuki
T
T
Kato
K
K
Takahashi
T
T
Yanagisawa
T
T
D004562:Electrocardiography; D006801:Humans; D009203:Myocardial Infarction / Q000000981:diagnostic imaging* / Q000473:pathology; D009206:Myocardium / Q000473:pathology; D013794:Thallium Radioisotopes; D015899:Tomography, Emission-Computed, Single-Photon
D013794:Thallium Radioisotopes