The evaluation of ventricular function using gated myocardial imaging with Tc-99m MIBI

Abstract

Left ventricular function is an important prognostic indicator in patients with coronary artery disease. We have assessed a method of providing this information as an adjunct to myocardial perfusion imaging using Tc-99m MIBI (2-methoxy-2-methyI-isopropyl-l-isonitrile). Two separate studies, at rest and during exercise, were performed following an injection of 400-600 MBq of Tc-99m MIBI in 62 patients. Cardiac gating permitted excellent myocardial edge definition during the cardiac cycle. Radionuclide fractional shortening (RFS) was calculatedfrom the anteroposterior (AP) and the septum to lateral wall (SL) axes in diastole and systole. Results were compared with echocardiographic fractional shortening (EFS) and the ejection fraction (EF) obtained from the gated equilibrium blood pool using Tc-99m-labelled red blood cells. The RFS in the AP axis correlated closely with echocardiographic FS (r = 0.89, P <0001). The RFS in both axes was averaged to provide a global RFS. Global RFS correlated closely with LV radionuclide EF (r = 0.83, P <0.001). Inter- and intra-observer reproducibility studies have shown a variability for the procedure of <10%. In conclusion, gated perfusion imaging with Tc-99m MIBI, provides useful functional information as an adjunct to perfusion imaging.