Attenuation correction improves the detection of viable myocardium by thallium-201 cardiac tomography in patients with previous myocardial infarction and left ventricular dysfunction

The aim of this study was to determine the influence of attenuation-corrected thallium-201 stress/redistribution/reinjection single-photon emission tomography (SPET) on the number of viable segments in patients with previous myocardial infarction and dysfunctional myocardium. Fifty-one patients with previous myocardial infarction and left ventricular dysfunction were included in the study. In all patients, Tl-201 non-corrected (NC) and attenuation-corrected (AC) SPET was performed using a stress/redistribution/reinjection protocol followed by coronary angiography, A semiquantitative analysis was performed using polar maps for NC and AC stress, redistribution and reinjection short-axis and vertical long-axis (apex) slices. Severe (perfusion defect below 50%/maximal count rate: PD<50), mild and moderate persistent defects for redistribution and reinjection were evaluated for both NC and AC studies. A total of 1581 segments were evaluated by semiquantitative segmental analysis for both NC and AC studies for each redistribution and reinjection map. In the redistribution maps, NC revealed a total of 352 segments and AC a total of 222 segments with impaired perfusion below 50% of the maximal count rate (PD<50). The mean number of affected segments was 6.9 +/- 5.5 in the case of NC and 4.4 +/- 4.8 in the case of AC (P < 0.001), In the reinjection maps, NC revealed a total of 263 non-viable segments (PD<50) and AC a total of 169 non-viable segments. The mean number of affected segments was 5.2 +/- 5.3 in the case of NC and 3.3 +/- 4.2 in the case of AC (P < 0.001), Recovery of function was better predicted by AC than by NC in 20% of patients in the follow-up group. Therefore, the use of attenuation correction influences the extent of viable segments by showing more viable segments in either redistribution or reinjection maps. Tl-201 imaging without attenuation correction may underestimate the extent of tissue viability, which may contribute to the lower sensitivity compared to fluorine-18-fluorodeoxyglucose positron emission tomography, where attenuation correction is a routinely performed procedure.