Duration of abnormal SPECT myocardial perfusion imaging following resolution of acute ischemia: an angioplasty model.

Abstract

This study was designed to determine how long nuclear myocardial perfusion imaging (MPI) remains abnormal following transient myocardial ischemia. Acute rest MPI identifies myocardial ischemia with a high sensitivity when the radionuclide is injected during chest pain. However, the sensitivity of this technique is uncertain when the radionuclide is injected following the resolution of symptoms. Forty patients undergoing successful coronary angioplasty were randomized into four equal groups. Tc-99m sestamibi was injected intravenously during the last balloon inflation (acute MPI) in 30 patients and then reinjected 1, 2, or 3 h later (delayed MPI). In a fourth group, the radiopharmaceutical was injected at 15 min following balloon deflation (delayed MPI). A final injection was performed at 24 to 48 h (late MPI) in 37 patients (93%). A perfusion defect was detected in all 30 acute MPI studies; in 7/10 patients (70%) injected at 15 min; in 11/30 patients (37%) injected at 1, 2, or 3 h; and in 7/37 patients (19%) injected at 24 to 48 h. Perfusion scores were 13.0 +/- 9.2 on acute MPI, 5.1 +/- 2.8 at 15 min (p < 0.001 vs. acute MPI); 2.6 +/- 3.0 at 1, 2, and 3 h (p < 0.001 vs. acute MPI); and 1.3 +/- 2.4 at 24 to 48 h (p < 0.001 vs. acute MPI; p < 0.03 vs. delayed MPI). Myocardial perfusion imaging may remain abnormal for several hours following transient myocardial ischemia even when normal flow is restored in the epicardial coronary artery.