Direct correlation between regional systolic function and regional washout rate of 99mTc-sestamibi in patients with idiopathic dilated cardiomyopathy

OBJECTIVE: Although a higher washout of ⁹⁹mTc-sestamibi (MIBI) from the ischemic myocardium was reported, little is known about it in idiopathic, nonischemic dilated cardiomyopathy (DCM). Using a quantitative electrocardiographic-gated single-photon emission computed tomography strategy, regional myocardial function may be obtained in conjunction with regional tracer perfusion. The aim of this study was to investigate the significance of regional washout of MIBI compared with regional systolic function in patients with DCM. METHODS: Rest quantitative electrocardiographic-gated single-photon emission computed tomography was performed in 20 patients with DCM who had no significant coronary stenosis on coronary angiogram and in five normal volunteers. single-photon emission computed tomography imaging was observed at 30 min and 4 h after 740 MBq of MIBI injection, and the regional washout rate (WR) was calculated using a 20-segment model. RESULTS: The mean global ejection fraction was 28.2 ± 12.4% and the mean end-diastolic volume was 177 ± 78 ml. The myocardial segments were divided into three groups on the basis of the mean WR of normal volunteers: group A (n=164): WR ≥ 25.4% (=mean+SD); group B (n=138): 19.6% ≤ WR < 25.4%; group C (n=98): WR<19.6% (=mean-SD). The regional wall thickening of group A segments was significantly less than that of the other groups (11.6 ± 0.7 vs. 14.0 ± 0.9 and 14.9 ± 0.7%, respectively, P<0.05). The global left ventricular ejection fraction showed significant negative correlation to the extent of group A segments per patient (R=-0.65, P<0.005), indicating that higher washout was the result of decreased systolic function in DCM hearts. CONCLUSION: Regional higher WR of MIBI may indicate a significant marker for myocardial damage in asymptomatic to mildly symptomatic patients with DCM.