Introduction: Dobutamine stress echocardiography (DSE) and myocardial perfusion scan (MPS) are commonly used to detect viable myocardium. We designed this study to compare the results of these two methods in detecting myocardial viability.
Methods: We studied 736 segments from 46 patients (42 men, mean age 56 years), with coronary artery disease and impaired left ventricular systolic function (ejection fraction <40%), using low-dose DSE and (99m)Tc-sestamibi MPS. The two methods were compared in the detection of viability, primarily in dysfunctional and secondarily, in different anatomical segments.
Results: Of the 736 segments, 397 (53.9%) were normal or mildly hypokinetic and 339 (46.1%) dysfunctional. Of 49 severely hypokinetic segments, 33 (67.4%) were viable and 1 (2%) nonviable according to both methods, while discordant results were found in 15 (30.6%). Among 274 akinetic segments, both methods were concordant in 148 (54%) nonviable and 15 (5.5%) viable regions, while 111 (40.5%) segments showed discordance. Of 16 aneurysmal segments, 7 were viable according to MPS, but none showed contractile reserve on DSE. The two methods were concordant in 14.2% viable, 46.6% nonviable and discordant in 39.2% of all dysfunctional segments. Eighty-seven percent (98/113) of akinetic and 20% (8/41) of hypokinetic segments had 99mTc-sestamibi uptake, but did not show contractile reserve. There was more than 75% agreement in lateral basal, anterior apical and inferior apical segments.
Conclusion: The proportion of segments showing a positive response to dobutamine is significantly lower than those with technetium uptake. This suggests that the cellular mechanisms responsible for a positive inotropic response to adrenergic stimulation required a higher degree of myocyte functional integrity than those responsible for 99mTc-sestamibi uptake.