Description

A reverse redistribution pattern in rest thallium-201 (Tl)/stress technetium-99 m (Tc) tetrofosmin single photon emission CT (SPECT) is confusing. We present a myocardial perfusion SPECT in a 40-year-old patient undergoing coronary intervention in the left anterior descending coronary artery with an acute coronary syndrome. This pattern depicts a nearly normal perfusion in a resting Tl image and a perfusion defect in a stress Tc image, which indicates stress-induced ischaemia without significant coronary stenosis. This is frequently seen in patients who underwent an emergent reperfusion therapy. A nearly normal perfusion in a resting Tl image frequently changes into a perfusion defect mimicking a stress image in a 24 h delayed image (figure 1). This phenomenon can be explained by an excessive washout of Tl and Tc from the reperfused myocardium. Tl washout after reperfusion is well known as reverse redistribution.1 Washout of Tc agent is also reported in reperfused myocardium.2 In a rest Tl/stress Tc protocol, time course between the injection and imaging would be one of the reasons for reverse redistribution. A Tl/Tc protocol always requires rest-first imaging just after the Tl injection; this shorter time duration would not be enough for excessive washout. Therefore, a resting Tl image shows nearly normal perfusion. Conversely, post-stress images usually acquired 1 h after the injection for avoiding the emission of liver uptake. A 24 h delayed Tl image is enough to show reverse redistribution and it is an important procedure which can prevent misinterpretation after emergent percutaneous coronary interventions.

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Figure 1

Upper line: technetium-99 m (Tc) short axis images at post-stress showing a distal anteroseptal perfusion defect. Middle line: thallium-201 (Tl) short axis images at rest showing nearly normal perfusion. These images are interpreted as an evidence of ischaemia. Lower line: 24 h late Tl images showing a reverse redistribution pattern in the same area of Tc short axis images. In comparison to the Tc images, the interpretation changed to non-reversible perfusion defect which indicated an infarcted myocardium without ischaemia.