Prediction of reversibility of chronic ischemic myocardial dysfunction: comparative accuracy of rest early and delayed redistribution thallium-201 tomography and low-dose dobutamine echo-cardiography

ABSTRACT

The current study sought to directly compare the diagnostic accuracy of rest early- and delayed thallium single-photon emission computed tomography and low-dose dobutamine echocardiography for prediction of contractile recovery of hibernating myocardium after coronary revascularization.Thallium SPECT and dobutamine echocardiography permit differentiation of viable from non-viable myocardium. However, few studies have directly compared their accuracy in the same patients.Twenty eight consecutive patients [22 men and 6 women, aged 39 to 71 years; mean 58 +/- 8 years] with old anterior myocardial infarction, and rest ischemic segmental ventricular dysfunction [potentially hibernating myocardium] underwent rest early-and delayed redistribution thallium SPECT and low-dose dobutamine echocardiography before coronary re-vascularization. Recovery of segmental and global dysfunction was assessed by echocardiography 1l +/- 2 weeks after re-vascularization. For analysis, the left ventricle was divided into 16 segments and regional wall motion was graded semi-quantitatively [I = normal, 2 = hypokinetic, 3 = akinetic, and 4 = dyskinetic]. Percent thallium activities were quantified, using circumferential profiles as early [I0-minute] and delayed [l7-hour] and expressed as a percentage of maximal activity in each projection, using the same 16-segment model. Before revascularization, 82 segments were grouped as normal [normal segment function and coronary stenosis <70%, group I]; in the remaining segments with coronary stenosis >/= 70%, 176 segments had normal function [group II], and 190 segments showed rest dysfunction [group lll]. Early and delayed thallium-20I regional percent activities did not differ in group I and in group II but were significantly less in group III. Segments with improved wall motion during dobutamine infusion had more significant early and delayed thallium-20I uptakes than unresponsive segments. Of the 190 initially dysfunctional segments, 117 segments [62%] resumed functional recovery at follow-up after revascularization. The diagnostic accuracy of the two techniques was studied both for global function [individual patient] and for individual segmental function. Global functional analysis showed that left ventricular ejection fraction rose by >/= 9% in 15 patients [59%] and rose significantly from a mean value of 38 +/- 8 to 46 +/- I0 after revascularization. Early and delayed thallium SPECT and low-dose dobutamine echocardiography had sensitivities of 75%, 80% and 90%; respectively, and specificities of 45%, 77% and 82%, respectively, for prediction of post-revascularization global functional recovery. Thus, only early thallium-20I SPECT was significantly less specific [P < 0.001] than both delayed thallium-20I SPECT and dobutamine echocardiography in prediction of unrecovered global left ventricular function after revascularization. Segmental functional analysis showed that all modalities had comparable sensitivities 78%, 87% and 87%; respectively [P > 0.05]. Meanwhile, both delayed thallium-20I SPECT and dobutamine echocardiography were significantly highly specific [84% and 79%; respectively, P > 0.05] than early thallium-20I SPECT [49%, P < 0.001] in prediction of unrecovered segmental wall function after revascularization. The predictive accuracy of the three modalities was 67%, 86% and 84%, respectively.The current study indicated that both delayed thallium-201 SPECT and low-dose dobutamine echocardiography had comparable sensitivity, specificity and accuracy in prediction of hibernating myocardium. Meanwhile, early thallium-20I was equally sensitive by significantly less specific and accurate than the earlier modalities for prediction of hibernating myocardium