LAUSR

In the field of nuclear cardiology we have three imaging modalities to measure ventricular function: first-pass radionuclide angiography (FPRNA), equilibrium gated radionuclide angiography (ERNA), and ECG-gated myocardial perfusion imaging SPECT (GSPECT) or PET studies. GSPECT was introduced in the 1980s and is considered an ideal technique for combined evaluation of myocardial perfusion and left ventricular function from a single study. Automation of the image processing and quantification has made this technique practical and highly reproducible. In patients with known or suspected coronary artery disease, gating enhances the diagnostic and prognostic capability of myocardial perfusion imaging and provides incremental information over the perfusion data. During a GSPECT study, a perfusion tracer is injected and is taken up by the LV myocardium. The definitions of the LV myocardium and the LV cavity are achieved by delineating both the endocardium as well as the epicardial edges on the perfusion image. LV regional and global contractile functions are quantified based on the changes in the LV volume, excursion of the endocardium, and brightening of the myocardium from the ECG-gated end-diastole to end-systole. LV volumes and LVEF are usually obtained by applying commercially available software to the reconstructed gated dataset. Software packages developed at Cedars-Sinai Medical Center (QGS), University of Michigan (4D-MSPECT), and Emory University (Emory Cardiac Toolbox) are available in many nuclear cardiology labs. Direct comparison between these software packages reveals good correlations in LV volumes as well as LV functional measurements. In addition to identification of perfusion abnormalities, gated SPECT offers evaluation of systolic functional parameters including LVEF, LVED, and LVES volumes. GSPECT also allows assessment of diastolic parameters such as the peak ejection rate (PER), peak filling rate (PFR), time to peak filling rate (TPFR), and mean filling rate during the first third of diastole (MFR/3). Both systolic and diastolic functional parameters obtained from GSPECT have been validated against similar parameters obtained from other imaging modalities. Other parameters such as transient ischemic dilatation (TID), lung-to-heart (L/H) ratio, and intraventricular synchrony have also been shown to add valuable clinical and prognostic information. The introduction of ECG gating to MPI allowed the simultaneous assessment of myocardial perfusion and function from a single study. Both global and regional systolic functions have incremental prognostic value over perfusion variables alone. Also, adding ESV or EF to summed stress score (SSS) better predicts mortality in both men and women. On stress SPECT studies, perfusion images capture myocardial perfusion distribution at peak stress, while gated images demonstrate LV contractile function at the time of acquisition. Patients with particularly severe coronary artery disease may show post-stress stunning on SPECT MPI, with regional and global LV dysfunction seen on post-stress images, Reprint requests: Adel Hassan Allam, MD, FASNC, Cardiology, Faculty of Medicine, Al-Azhar University, Cairo, Egypt; [email protected] J Nucl Cardiol 2018;25:661–4. 1071-3581/$34.00 Copyright 2017 American Society of Nuclear Cardiology.