Comparison of GTN Enhanced Gated MIBI SPECT with Dobutamine Stress Echocardiography for the Assessment of Hibernating Myocardium
The techniques for non-invasive assessment of myocardial viability include Dobutamine Stress Echocardiography (DSE)& GTN enhanced Tc-99m Gated MIBI SPECT (GTN-GMS). We compared GTN-GMS with DSE to assess the efficacy of GTN-GMS in evaluation of hibernating myocardium.The study was done in 19 patients(mean age 53.42 ± 7.67) with known coronary artery disease (CAD) & LVEF < 45 %. All patients underwent 3 studies on separate days; rest Tc-99m GMS, GTN-GMS and DSE. Images were split in 17 segments and 5-point grading system (0-4) for perfusion and 6-point grading system (0-5) for wall motion was used to interpret the results. Statistical analysis was done with the help of Cohen’s Kappa test & Pearson’s Correlation Co-efficient. Results: Comparison of rest wall motion and GTN enhanced wall motion also revealed significant improvement in wall motion on GTN enhancement (Kappa value=0.56). Comparison of baseline ECHO and DSE wall motion showed that DSE plays a substantial role in unmasking hibernating myocardial segments (Kappa value=0.52). Comparison of GTN enhanced wall motion and DSE wall motion showed good concordance (Kappa value=0.52) and correlation (r=0.96). Moreover, it was observed that the segments showing improvement in wall motion on DSE, also showed improvement in perfusion on GTN-GMS (r=0.93), although this comparison was done arbitrarily. Thus, in patients with chronic CAD & impaired LVEF, GTN-GMS improves the differentiation between viable myocardium & irreversibly fibrotic tissue. Moreover, both GTN-GMS & DSE give comparable results as far as detection of hibernating myocardium is concerned.