High prevalence of the thallium-201 reverse redistribution phenomenon in patients with syndrome X

To evaluate the stress-myocardial perfusion pattern in patients with angina, positive exercise test and angiographically smooth coronary arteries (syndrome X).

Prospective study.

Twenty-five consecutive patients (seven males, mean age 54 +/- 8 years) with typical angina, positive exercise test, normal coronary arteries and no inducible spasm, underwent stress-redistribution thallium-201 myocardial perfusion scintigraphy. Thirty-two consecutive patients (14 males, mean age 49 +/- 7 years) with atypical chest pain and negative exercise test, undergoing stress-redistribution thallium scan, served as controls.

Exercise was discontinued for angina and/or ST-segment depression after 12 +/- 3 min. Thallium stress images revealed 40 hypoperfused segments in 27 patients (77%); after 4 h, 16 of these segments had completely normalized, 10 remained unchanged, six exhibited partial reperfusion and eight worsened. Twenty-four patients (69%) exhibited thallium reverse redistribution in 33 segments. Thirty-four patients (97%) had at least one hypoperfused segment in one of the two scintigraphic phases. Of the 24 patients with reverse redistribution, eight also underwent stress-rest 99m Tc-MIBI SPECT: six exhibited reduced tracer uptake that was present at rest, but not on stress images, in the same segments showing thallium reverse redistribution. Thallium stress images revealed four hypoperfused segments in three controls (9%); at redistribution, one segment normalized, two remained unchanged and one exhibited partial reperfusion. Additionally, there were four new underperfused segments appearing on redistribution in four patients (13%). Overall, there were seven controls (22%) with at least one hypoperfused myocardial segment in one of the two scintigraphic phases.

Our study confirms that perfusion abnormalities are present in most syndrome X patients. Additionally, the data show that reverse redistribution (a perfusion defect that develops or becomes more evident on delayed imaging) is a common finding in these patients. The mechanisms of the phenomenon remain obscure: we suggest that it is due to inhomogeneous perfusion, and the hyperaemic response induced by exercise masks resting underperfusion of certain areas.