Comparison of Dobutamine Echocardiography with Positron Emission Tomography for the Assessment of Hibernating Myocardium

Dobutamine infusion during echocardiographic imaging (DE) has been proposed as an alternative to Positron Emission Tomography (PET) for the assessment of hibernating myocardium. The purpose of this study was to compare the two techniques for the detection of hibernating myocardium in canine model. Six dogs underwent ligation of the left anterior descending (LAD) coronary artery and placement of sonomicrometer crystals in the are subtended by the distal LAD and circumflex coronary artery. The animals were subsequently brought back to the lab for series of 4 DE (3 days, 1-2-4 weeks post ligation) during which dobutamine (2.5-30 μg/kg/min) was given with continous echocardiographic and sonomicrometric monitoring. Just prior to the last DE PET scan was performed utilizing F-18 FDG and N-13 NH3. Following the final DE the LAD was bypassed and flow restored. The myocardium was defined as hibernating if there was improvement in wall motion (echo), or segment shortening (sonomicrometer) following bypass. By PET viable myocardium was defined as normal or mildly decreased activity of FDG in the infarct zone. At the conclusion of the protocol the animals were sacrificed and the heart excised, sliced into sections and stained with TTC to determine myocardial infarct size. The results are summarized in the table where (S) = sono, (E) = echo, (P) = PET, (+) = viable, and (−) = nonviable. Thus there was agreement between all tests in animals. In Dog 6 there was agreement between S and E but not P. In this animal transmural infarction was found by TTC staining and there was no improvement in function following bypass. Conclusion: There is good concordance between DE and PET for the assessment of hibernating myocardium. PET FDG may be overly sensitive for the detection of functional recovery following revascularization.