Evaluation of left ventricular volumes and ejection fraction by automated gated myocardial SPECT versus cardiovascular magnetic resonance

Summary Background:  Electrocardiogram‐gated myocardial single‐photon emission computed tomography (SPECT) with 99m Tc‐tetrofosmin allows simultaneous evaluation of myocardial perfusion and function. In this study, left ventricular volumes, ejection fraction (LVEF), and left ventricular wall volume (LVWV) derived from gated SPECT were compared with measurements from cardiovascular magnetic resonance (CMR), performed within a few hours. Methods:  The study population included 55 patients with known or suspected coronary artery disease, including 13 patients with recent acute myocardial infarction. End‐diastolic (EDV) and end‐systolic (ESV) volumes, LVEF and LVWV were derived automatically from gated SPECT using commercially available software (QGS). In the CMR studies, manually delineated endocardial and epicardial borders on short‐axis slices were used to calculate the volumes. Results:  Gated SPECT underestimated EDV by 35 ± 14 ml (mean ± SD) ( P <0·001), ESV by 10 ± 13 ml ( P <0·001), and LVEF by 4 ± 7 percentage points ( P <0·001). There were no systematic difference in EDV, ESV or LVEF between the methods. SPECT underestimated LVWV by 49 ± 30 ml ( P <0·001), with a trend towards increasing underestimation by SPECT for larger wall volumes. Conclusion:  These findings show that gated SPECT slightly underestimates EDV, ESV and LVEF compared with CMR. This underestimation is systematic, however, indicating that ventricular volumes derived from gated SPECT are robust enough to guide clinical management. Estimates of LVWV in patients with large wall volumes are less accurate.