Simultaneous measurement of myocardial perfusion and ventricular function during exercise from a single injection of technetium-99m sestamibi in coronary artery disease. New radiopharmaceuticals permit simultaneous assessment of myocardial perfusion and left ventricular function using a single tracer injection. The purpose of this study was to quantitate the relation between myocardial perfusion and function at rest and during exercise in patients with documented coronary artery disease (CAD). A rest first-pass radionuclide angiocardiogram (RNA) was recorded in 51 patients with CAD during injection of 10 mCi of technetium-99m (Tc-99m) sestamibi, and tomographic perfusion images were obtained 60 minutes later. A treadmill test was then performed, and on attainment of an exercise end point a second first-pass RNA was recorded with 30 mCi of Tc-99m sestamibi. Tomographic images reflecting myocardial perfusion during exercise were obtained 1 hour later. Tomographic perfusion defect size, quantified using modifications of the Cedars-Sinai program, correlated directly with end-systolic volume and inversely with ejection fraction at rest and during exercise. However, perfusion defect size often varied widely in patients with similar left ventricular function. This independence between measurements of perfusion and function suggests that simultaneous assessment of the 2 physiologic variables could improve the diagnostic and prognostic information of radionuclide tests. 