Underestimation of regional myocardial perfusion with Tc-99m sestamibi single-day rest-stress SPECT - A "drug washout" pitfall?

Myocardial perfusion scintigraphy with a Tc-99m sestamibi single-day SPECT protocol is a widely used technique to examine patients with possible or kn own coronary artery disease. A 76-year-old man with a clinical history sugg estive of ischemic heart disease underwent Tc-99m sestamibi myocardial SPEC T imaging with a same-day rest and stress protocol after temporary disconti nuation of his current therapy, which included calcium channel and beta blo ckers and nitrates. The scintigraphic pattern was consistent with an asympt omatic infarction of the posterolateral myocardial wall and periinfarct isc hemia, One week later, the patient had a Tc-99m sestamibi myocardial SPECT study at rest without discontinuing therapy, and scintigraphic images showe d normalization of the posterolateral wall perfusion defect. The angiograph ic study showed a 90% stenosis of the circumflex artery. This case suggests that, during a 1-day cardiac SPECT protocol, washout of therapeutic pharma ceuticals may be responsible for underestimation of myocardial rest perfusi on in territory supplied by a coronary artery with a critical stenosis.