SCINTIGRAPHIC ASSESSMENT OF SILENT-MYOCARDIAL-ISCHEMIA AFTER EARLY INFARCTION USING MYOCARDIAL SPET IMAGING WITH TL-201 AND I-123 MIBG

To test the hypothesis that myocardial sympathetic denervation reflect s silent myocardial ischaemia early after infarction, 12 patients with myocardial infarction but without post-infarction angina pectoris und er-went single photon emission tomography (SPET) at rest with Tl-201 a nd I-123-metaiodobenzylguanidine (MIBG) shortly after and 3 months aft er infarction. Short-axis SPET images at the basal, mid-ventricular an d apical portions of the left ventricle were selected, and each short- axis image was divided into eight segments. Tracer uptake in each of t he 24 segments was scored using a 4-point scale. The total score in ea ch segment was calculated as the defect score for each image, and the difference between the total defect score for the Tl-201 and I-123-MIB G images was calculated as the Delta defect score. All 12 patients und erwent exercise stress Tl-201 scintigraphy 1 month after infarction, a nd they were divided into two groups: those patients with (Group A, n = 7) and those patients without (Group B, n = 5) transient perfusion d efects in the peri-infarcted region without chest pain. For the I-123- MIBG defect score, a marked reduction at 3 months was observed in Grou p A (24 +/- 12 vs 13 +/- 6; P < 0.01), whereas the defect score remain ed unchanged in Group B (25 +/- 7 vs 23 +/- 8; N.S.). The Delta defect score was significantly reduced in Group A (10 +/- 5 vs 6 +/- 4; P < 0.05), whereas it remained unchanged in Group B. The I-123-MIBG defect score early after infarction was higher than the exercise-induced Tl- 201 defect score (24 +/- 12 vs 20 +/- 9; P < 0.01), whereas at 3 month s post-infarction it was lower than the exercise-induced Tl-201 defect score (13 +/- 6 vs 20 +/- 9; P < 0.05). Moreover, effort chest pain d uring daily activities was noted in 5 of the 7 (71%) patients in Group A within 3 months post-infarction. The results of this study suggest that viable but denervated myocardium (mismatched I-123-MIBG defects) is present in peri-infarcted regions, and that myocardial sensory nerv ous disturbance, which may co-exist with sympathetic nervous denervati on, may induce silent myocardial ischaemia in patients with myocardial infarction.