Thallium gated SPECT: relation between immediate post-stress evolution of ejection fraction and severity of perfusion pattern.

Background and aims A significant decrease of left ventricular ejection fraction (LVEF) at stress has been reported with 99 Tc m gated single-photon emission computed tomography (gSPECT) in severe myocardial stunning up to 1 h after exercise. This study was designed to show whether 201 Tl gSPECT can measure LVEF evolution from rest to stress in routine examination and give additional information to perfusion interpretation since acquisition starts immediately after stress test. Methods Post-exercise and rest 201 Tl gSPECT were performed in 187 patients with suspected coronary artery disease. Myocardial perfusion was quantified by 20-segment analysis. Patients were divided into four groups according to their summed perfusion score, reversibility rate and electrocardiographic findings, i.e. in order of severity: I = normal perfusion, II = fixed defect owing to a myocardial infarction, III = full reversible ischaemia, and IV = partial reversible ischaemia. LVEF was calculated by Germano's automatic algorithm. Results Normal subjects (n=29) and infarcted patients (n=34) showed a significant LVEF increase between rest and stress, +7±9% and +5±7% respectively. In full reversible ischaemic patients (n=46), stress LVEF showed no increase (+1±8%) and this group was statistically different from both group I and group II. Furthermore, when ischaemia was partially reversible (n=31), LVEF decreased significantly (-3±8%), particularly when exercise tests were abnormal (-4±8%). Group IV was statistically different from groups I and II. Conclusions Good agreement exists between the severity of ischaemic perfusion pattern and LVEF degradation at stress, which is consistent with previously published data using 99Tcm gSPECT. Additionally, the use of 201 Tl for immediate post-exercise imaging allows the observation of a physiological LVEF increase in normal and infarcted patients.