RELATIONSHIP OF GATED SPECT VENTRICULAR-FUNCTION PARAMETERS TO ANGIOGRAPHIC MEASUREMENTS

Objectives, Left ventricular volumes and ejection fractions constitute important information in the diagnosis of cardiac disease. This inves tigation examined the relations of functional parameters computed with a recently published scintigraphic gated tomographic method with thos e from angiography, analyzing discrepancies arising from differences i nvolved in modeling the left ventricle. Background, While left ventric ular ejection fractions obtained from myocardial perfusion gated singl e-photon emission computed tomography (SPECT) have demonstrated accura te comparisons with other imaging modalities, validations of volumes h ave not been examined as extensively, and some recent studies have rep orted a wide range of angiographic correlation. It is important to kno w how volumes obtained by a new class of methods compare with those fr om older, well-established techniques in order to interpret individual patients' results, particularly when scintigraphic images are severel y hypoperfused, Methods and Results, Tc-99m sestamibi myocardial perfu sion gated SPECT data were processed retrospectively for 58 patients s tudied by single-plane angiography, Endocardial borders were generated automatically on paired vertical and horizontal long-axis Tc-99m sest amibi gated tomograms for computing ventricular volume using a Simpson 's rule summation of elliptical slices. Linear regression and paired t tests were used to compare SPECT with angiographic parameters for all patients and for groups identified on the basis of tomogram visual ex amination as hypoperfused, ischemic or nonischemic, with the latter ca tegory further subgrouped as to fixed defects or normal perfusion. Lin ear regression analysis demonstrated Pearson correlation coefficients of 0.87 for end-diastolic volumes, 0.91 for end-systolic volumes, and 0.86 for ejection fraction; paired t test analysis showed end-systolic volumes to be nearly identical (p > 0.99) to angiographic values. How ever, paired t tests also revealed gated SPECT end-diastolic volumes a nd ejection fractions were significantly lower (p < 10-4) than angiogr aphy, Correlations and trends were essentially the same for all subgro ups except for the small sample (n = 10) of patients with normal perfu sion. Conclusions. Gated SPECT provides ventricular volumes and ejecti on fractions that correlate well with angiography, even in hypoperfuse d and ischemic populations. However, gated SPECT end-diastolic volumes and ejection fractions are significantly lower than angiographic meas urements, partly because of inclusion of greater outflow tract amounts in standard angiographic models. Because myocyte concentration decrea ses rapidly at the ventricular base, it is likely that most gated SPEC T methods will produce endocardial borders encompassing less of the ou tflow tract than do angiographic outlines.