Reverse redistribution phenomenon on rest (99m)Tc-tetrofosmin myocardial single photon emission computed tomography involves impaired left ventricular contraction in patients with acute myocardial infarction.

The purpose of this study was to investigate the clinical significance of the reverse redistribution (RR) phenomenon on technetium-99m ((99m)Tc)-tetrofosmin myocardial single photon emission computed tomography (SPECT) performed at rest. Twenty-five patients underwent myocardial SPECT 3 weeks after the onset of acute myocardial infarction. Myocardial images were acquired at 40 min (early) and 4 h (delayed) after the injection of 740 MBq of (99m)Tc-tetrofosmin. The regional myocardial uptake of the tracer in 26 segments of the left ventricular (LV) wall was visually scored from 0 (no activity) to 3 (normal activity), and then the RR was defined as a decrease of more than 1 point in the activity score on the delayed image compared with that on the early image. Regions with an activity score of 3 on both the early and delayed images were defined as normal, and those with a score of 0 or 1 on the early image were considered to have a fixed defect. The regional myocardial (99m)Tc-tetrofosmin uptake and washout rate were also quantitatively assessed in each region. In addition, exercise stress electrocardiograph-gated SPECT with (99m)Tc-tetrofosmin was performed within 1 week of the rest study, and the percent count increase (%CI) during myocardial contraction in each corresponding region was studied. RR was observed in 18 of the 25 patients. The regional washout rate of (99m)Tc-tetrofosmin was significantly higher in the RR regions (45.0+/-3.8%) than in either the normal regions (36.4+/-4.1%, p<0.001) or in those with a fixed defect (39.7+/-3.9%, p<0.001). The %CI in the RR regions (10.4+/-10.4%) was significantly less than that in the normal regions (23.5+/-10.1%, p<0.001); however, no significant difference was found between the RR regions and those with a fixed defect (8.0+/-7.2%). In patients with acute myocardial infarction, the regions showing the RR phenomenon on (99m)Tc-tetrofosmin SPECT have severely impaired LV wall contraction after exercise.