Objective The aim of this study was to investigate the correlation between myocardial viability in old myocardial infarction as assessed by treadmill exercise test and 99mTc-MIBI/18F-FDG dual isotope simultaneous acquisition of single photon emission CT (SPECT).
Methods 15 consecutive patients (13 males, 2 females, mean age 55±8years) with old myocardial infarction were included in this study. All patients underwent coronary arteriography, maximal treadmill exercise testing and 99Tcm-MIBI/18F-FDG SPECT. Patients were classified into myocardial viability group and non myocardial viability group according to 99Tcm-MIBI/18F-FDG SPECT. The semi-quantitative scoring system was used for SPECT images. Myocardial viability was defined as an improvement of perfusion at least >1 grade in at least two contiguous segments during 18F-FDG SPECT. The indices of treadmill exercise testing were measured and compared in myocardial viability and non myocardial viability groups. Compared with the results of 99Tcm-MIBI/18F-FDG SPECT, the sensitivity and specificity of these indices for detecting of myocardial viability were calculated.
Results 8 out of the 15 studied patients were defined as myocardial viability group, and the rest of 7 patients were in non myocardial viability group. 7 out of 8 (87%) patients in myocardial viability group were accompanied with exercise-induced Q-wave prolongation. Myocardial viability was detected more often in patients with smaller QT dispersion (≤70 ms). Q-wave prolongation had well consistency with 99mTc-MIBI/18F-FDG SPECT for detecting myocardial viability (x2=8.04, p =0.009). The sensitivities, specificities, positive predictive values, and negative predictive values of Q-wave prolongation and QT dispersion ≤70 ms for evaluating myocardial viability were 87.5%, 85.6%, 87.5%, 85.6% and 75.0%, 71.4%, 75.0%, and 71.4%, respectively.
Conclusion In patients with old myocardial infarction, exercise-induced Q-wave prolongation and QT dispersion were related to myocardial viability identified with 99Tcm-MIBI/18F-FDG SPECT. Exercise-induced Q-wave prolongation and QT dispersion were found to be the sensitive and specific ECG marker for detecting of myocardial viability.