Clinical impact of arrhythmias on gated SPECT cardiac myocardial perfusionand function assessment

Background. We reported previously that mean quantified cardiac functional parameters computed by one gated single photon emission computed tomography (SPECT) technique were not significantly altered by common gating errors. However, it is not known to what extent other gated SPECT approaches that a re based on different ventricular modeling assumptions are influenced by ar rhythmias, nor are the effects of gating errors on visual analyses and thei r subsequent clinical implications known. Methods. Projection data for 50 patients (aged 64 +/- 12 years; 68% men; 76 % with myocardial perfusion defects) undergoing technetium-99m sestamibi ga ted SPECT who were in sinus rhythm during data acquisition were altered to simulate common arrhythmias, To determine quantitative effects, we performe d calculations for original control and altered images by Gaussian myocardi al detection (Quantitative Gated SPECT [QGS] program) and by wall thickenin g derived from gated perfusion polar maps (Emory Cardiac Toolbox program). To evaluate visual assessment in control and simulated-arrhythmia tomograms , 2 experienced blinded observers independently interpreted perfusion from polar maps and wall motion and thickening from tomographic cines, using a 4 -point scale. Results. Although mean functional parameters were scarcely altered, paired t tests showed ejection fraction fluctuations to be significantly different from control values, causing patients to change between abnormal and norma l ejection fraction categories (2% of patients by QGS and 14% by Emery Card iac Toolbox). Visual examination of QGS polar perfusion and function maps s howed changes for 72% of cases, although in only 4% were these considered t o have potential clinical consequences, The kappa statistic for visual anal ysis of concordance between control and arrhythmia readings showed that agr eement was "excellent" for perfusion, "good" for motion, and "marginal" for thickening. Conclusions. As with quantitative measurements, thickening is the parameter most prone to error in the presence of arrhythmias. It is important to tes t data for gating errors to avoid potentially erroneous measurements and vi sual readings.