[Assessment of left ventricular contraction kinetics by ECG-gated myocardial SPECT with 99mTc-MIBI: a new attempt with multi-plane long axial tomography].

To investigate left ventricular (LV) contraction kinetics, we performed ECG gated myocardial tomography (gated-SPECT) with 99mTc-MIBI (99mTc methoxy-2-isobutyl isonitrile) at rest. Data were obtained from 32 views and R-R interval was divided into 16. To clarify whether myocardial count change during systole (%CC) reflected LV wall thickening (%WT), we compared septal and posterior %CC in short axis image with %WT which were obtained by echocardiography. And %CC correlated well with %WT (r = 0.86, p < 0.01). In order to assess myocardial contraction kinetics in various parts of LV, multi-plane long axial tomograms were constructed in 10 normal subjects and 9 patients with myocardial infarction (MI). By multi-plane long axial tomography, LV was divided into 17 segments. In each segment %CC was calculated from time activity curves of myocardial count of 99mTc-MIBI. And the disparity of the appearance of peak count in each segment was also observed. In normal subjects %CC was greatest at apex and they decreased from apex to cardiac base. Besides %CC at lateral segments was greater than that in septal segments. Normal range of %CC was determined segment by segment. In normal subjects the intervals from ECG R-wave to peak count were not different in each segment. But in patients with MI they distributed in wide range and prolonged intervals were observed in segments with rest perfusion defect (infarcted segment). In patients with MI decreased %CC was observed in 91% of infarcted segments, in 83% of the segments with exercise induced ischemia and in 89% of the segments with 123I-BMIPP defects. These results indicated decreased %CC represented viable but compromised myocardium as well as necrotic myocardium. In gated-SPECT we obtained useful informations in addition to myocardial perfusion. But it took more than 30 minutes to perform. More experience will be necessary to ascertain the value of this technique.