The left ventricular ejection fraction (LVEF) and volume (LVV) are important variables in patients with coronary artery disease. Quantitative gated myocardial SPECT (QGS) permits the simultaneous assessment of perfusion, LVEF and LVV. However, the presence of a perfusion defect may influence the LVEF and LVV measured by QGS.

67 subjects (M/F=47/20; mean age: 60.2±12.4 years) underwent both QGS with Tc-99m MIBI and 2-D echocardiography (Echo) at less than 7 days apart. The LVEF and LVV were measured by Echo, using the modified Simpson's method, and by QGS, using the automatic software, AutoQUANT™. The QGS rest images were used to compare with the Echo.

The correlations between the QGS and Echo for LVEF, LVEDV and LVESV were good in all 67 subjects (r=0.781, 0.754 and 0.906, respectively, p<0.0001). In patients with no perfusion defect (n=34), the correlations between the QGS and Echo for LVEF, LVEDV and LVESV were good (r=0.689, 0.593 and 0.586, p<0.0001). In patients with a perfusion defect (n=33), the LVEF between the QGS and Echo was well correlated (r=0.777, p<0.0001), but the LVEF was higher by 7.1±8.7% from the Echo results. The LVEDV and LVESV by both QGS and Echo were also well correlated (r=0.804 and 0.929, respectively, p<0.0001), but the LVEDV and LVESV were higher from QGS by 17.9±34 and 16.9±25 mL, respectively. A Bland-Altman analysis showed the agreement between the QGS and Echo in patients without perfusion defect was better than for those with a perfusion defect.

The perfusion defect from QGS might affect the measurements of the LVEF and LVV; therefore, the QGS and Echo values are not interchangeable.