Agreement and disagreement between "metabolic viability" and "contractile reserve" in akinetic myocardium

Background, In patients with chronic coronary artery disease and depressed left ventricular function, assessment of residual viability in akinetic myocardium is important for therapeutic management. Intact perfusion, preserved metabolism, and presence of contractile reserve are different aspects of cellular viability. However, not all viable cells exhibit all characteristics; it is thought that contractile reserve is less often preserved compared with metabolic activity or intact perfusion, In this study we performed a direct comparison between perfusion imaging with thallium-201 single photon emission computed tomography (SPECT), metabolic imaging with F18-fluorodeoxyglucose SPECT, and assessment of contractile reserve with low-dose dobutamine echocardiography in akinetic myocardium, Methods and Results, Forty patients with depressed left ventricular function (mean left ventricular ejection fraction 31% +/- 16%) were studied, Resting echocardiography showed akinesis in 165 (32%) segments, Most (n = 154, 93%) of these segments demonstrated resting hypoperfusion, F18-fluorodeoxyglucose imaging revealed a perfusion-metabolism mismatch in 41 segments and a match in 113 segments, Contractile reserve was present in 33 (80%) of the segments with a perfusion-metabolism mismatch and in 7 (6%) segments with a match (P <.0005). Of the 11 segments with normal perfusion, only 5 (45%) showed contractile reserve. The agreement between SPECT and dobutamine echocardiography was 87%, Although 94% of the segments that were nonviable on scintigraphy did not show contractile reserve, the disagreement between SPECT and dobutamine echocardiography was caused mainly by the absence of contractile reserve in 27% of the segments that were viable on scintigraphy, Conclusion, This study shows a good agreement between SPECT and dobutamine echocardiography, although a substantial number of segments with preserved viability on SPECT do not exhibit contractile reserve, indicating underestimation of viability by dobutamine echocardiography compared with F18-fluorodeoxyglucose imaging.