Simultaneous assessment of myocardial viability and function for the detection of hibernating myocardium using ECG-gated 99Tcm-tetrofosmin emission tomography:: A comparison with 201Tl emission tomography combined with cine magnetic resonance imaging

The aims of this study were to evaluate the simultaneous assessment of myocardial viability and function for the detection of hibernating myocardium using ECG-gated Tc-99(m)-tetrofosmin single photon emission tomography (SPET), and to compare the technique with Tl-201 SPET in combination with cine magnetic resonance imaging (MRI). Fifteen patients aged 41-70 years with impaired left ventricular function (mean LVEF 23.4 +/- 8.1%) and three-vessel coronary artery disease were studied before and after coronary artery bypass grafting (CABG). The following investigations were performed within the 3 months before surgery: stress/redistribution and separate-day rest Tl-201 SPET with early and late imaging, stress and ECG-gated rest Tc-99(m)-tetrofosmin SPET, and resting cine MRI. Between 3 and 6 months post-surgery, stress/redistribution Tl-201 SPET and cine MRI were repeated. Tracer uptake in nine segments of the left ventricle was graded visually and by quantitative analysis. Myocardial motion and thickening were graded visually from cine MRI and from gated Tc-99(m)-tetrofosmmn SPET images. Segments were defined as hibernating pre-operatively if tracer uptake was moderately reduced or better but myocardial motion was severely hypokinetic or worse. The accuracy of pre-operative assessment was assessed by comparison with post-operative function assessed by MRI. The sensitivity and specificity for the prediction of functional improvement were 69% and 60% for late rest Tl-201 uptake combined with MRI; 58% and 62% for rest 99Tcm-tetrofosmin uptake combined with MRI; and 62% and 45% when gated Tc-99(m)-tetrofosmin SPET was used to assess both tracer uptake and wall motion. In 21 of 135 segments, contractile function could not be assessed by gated Tc-99(m)-tetrofosmin SPET because of inadequate tracer uptake; function was improved in 5 (25%) of these segments after CABG. In conclusion, the combined assessment of viability and function using ECG-gated Tc-99(m)-tetrofosmin SPET is feasible and it allows the assessment of hibernating myocardium with similar accuracy to the combination of ungated Tc-99(m)-tetrofosnlin SPET with MRI. Where tracer uptake is too poor for assessment of function, there is a low incidence of myocardial hibernation. However, ECG-gated Tc-99(m)-tetrofosmin SPET is not superior to Tl-201 SPET combined with cine MRI in the identification of hibernation. ((C) 1999 Lippincott Williams & Wilkins).