Immediate 201Tl reinjection: an alternative approach in myocardial perfusion scintigraphy? A comparison with contrast angiographic findings.

Thallium-201 (201Tl) stress-redistribution/reinjection imaging provides a reliable diagnostic approach in patients evaluated for myocardial ischaemia. Immediate reinjection of 201Tl after completing the stress images followed by imaging 1 h later shortens the investigation time to 2.5 h and may provide a novel approach. In this study, we validated the immediate reinjection approach in the assessment of myocardial perfusion and viability using contrast angiographic findings as the reference standard. We studied 114 patients with documented cardiac catheterization data using quantitative planar 201Tl stress/immediate reinjection imaging. The 201Tl findings were compared with contrast angiographic data, coronary arteriographic findings and electrocardiographic data. Myocardial regions were considered to be viable if they (1) showed normal or hypokinetic wall motion, (2) were supplied by patent coronary arteries or by occluded arteries with adequate collateral circulation, or (3) were not related to electrocardiographic infarct site. Myocardial regions were considered to be non-viable if they (1) showed akinetic or dyskinetic wall motion, (2) were supplied by occluded vessels with inadequate collateral circulation, or (3) were related to electrocardiographic infarct site. Of 280 regions with normal or hypokinetic wall motion, 47 (17%) regions showed persistent 201Tl defects compared with 21 of 26 (81%) regions with akinetic/dyskinetic wall motion (P < 0.0001). Of 318 regions supplied by patent vessels, 65 (20%) regions showed persistent 201Tl defects compared with 14 of 22 (64%) regions subtended by occluded vessels (P < 0.0001). When the 201Tl findings were compared with electrocardiographic infarct site, 37 of 259 (14%) remote regions showed persistent defects compared with 42 of 83 (51%) infarct-related regions (P < 0.0001). We conclude that persistent defects on 201Tl immediate reinjection images are significantly more often associated with severe left ventricular wall motion abnormalities, coronary artery occlusion and infarct-related regions. In particular, agreement between the wall motion approach and scintigraphic findings was excellent, with 21 of 26 akinetic or dyskinetic segments showing persistent defects and 233 of 280 normal or hypokinetic segments measured as viable by the reinjection technique, resulting in a sensitivity of 81%, a specificity of 83% and an overall accuracy of 83%. These findings show the potential of immediate 201Tl reinjection imaging for assessing myocardial perfusion and viability.