Underestimation of regional myocardial perfusion with Tc-99m sestamibi single-day rest/stress SPECT: a “drug washout” pitfall?

Myocardial perfusion scintigraphy with Tc-99m sestamibi single-day SPECT protocol is a widely employed technique in the management of patients with suspected or known coronary artery disese. A 76 year old male patient, with a clinical history suggestive for ischaemic heart disease, underwent Tc-99m sestamibi myocardial SPECT study with same-day rest/stress protocol after a standard drug washout. The scintigraphic pattern was consistent with silent necrosis of postero-lateral myocardial wall and peri-infarctual ischemia. One week later the patient performed a Tc-99m sestamibi myocardial SPECT study at rest without discontinuing therapy and scintigraphic images showed normalization of the postero-lateral wall perfusion defect. The angiographic study demonstrated a 90% stenosis of circumflex coronary artery. This case suggests that, during one-day cardiac SPECT protocol, drug washout may be responsable of underestimation of myocardial rest perfusion in territories supplied by a coronary artery with critical stenosis.