Gabriella Marcucci

Usefulness of Dobutamine Tc-99m Sestamibi-Gated Single-Photon Emission Computed Tomography for Prediction of Left Ventricular Ejection Fraction Outcome After Coronary Revascularization for Ischemic Cardiomyopathy

Gated single-photon emission computed tomography (SPECT) imaging allows analysis of myocardial perfusion and assessment of baseline global and regional left ventricular (LV) function and their changes during low-dose dobutamine infusion. The study examined whether the changes in LV ejection fraction induced by dobutamine and evaluated using technetium-99m sestamibi- gated SPECT predict the evolution of ejection fraction after revascularization in patients with ischemic cardiomyopathy. Thirty-seven patients underwent resting and dobutamine nitrate-enhanced sestamibi-gated SPECT before revascularization and baseline-resting sestamibi gated SPECT after intervention to assess global functional changes. A postrevascularization improvement in ejection fraction > or =5 U was defined as significant. At follow-up, ejection fraction increased significantly in 19 patients. According to receiver-operating characteristic curve analysis, an increase in ejection fraction > or =5 U during dobutamine was the optimal cutoff value for predicting a significant postrevascularization improvement, with 79% sensitivity, 78% specificity, and 78% accuracy. A significant correlation was found between dobutamine and postrevascularization ejection fraction (r = 0.85; p <0.0001). The increase in ejection fraction during dobutamine is a good predictor of an improvement in ejection fraction after revascularization. This represents another important diagnostic contribution obtained using gated SPECT imaging for the assessment of myocardial viability in patients with ischemic cardiomyopathy.

Prediction of functional recovery in patients with chronic coronary artery disease and left ventricular dysfunction combining the evaluation of myocardial perfusion and of contractile reserve using nitrate-enhanced technetium-99m sestamibi gated single-photon emission computed tomography and Dobutamine stress

This study aimed to assess whether contractile reserve evaluation using dobutamine gated single-photon emission computed tomography (SPECT) improves the capability of quantitative perfusion analysis to predict functional recovery of viable hibernating myocardium. Resting and dobutamine nitrate-enhanced technetium-99m sestamibi (sestamibi) gated SPECT studies were performed in patients with coronary artery disease who had left ventricular dysfunction. Tracer activity was quantified, and wall motion and thickening visually scored. Reversible dysfunction was identified with gated SPECT repeated after coronary revascularization. Using the best activity threshold, perfusion quantification achieved 85% sensitivity and 55% specificity. Contractile reserve detection was significantly less sensitive (64%, p <0.0005), but more specific (88%, p <0.00001) than perfusion quantification. However, in the subgroup of hypokinetic segments, the sensitivity of contractile reserve assessment was just slightly lower than perfusion quantification (72% vs 91%, p = NS), whereas specificity was significantly higher (94% vs 23%, p <0.00001). Conversely, in the adyskinetic segments, perfusion quantification was significantly more sensitive than contractile reserve (82% vs 59%, p <0.005), but similarly specific (76% vs 85%, p = NS). Therefore, the identification of reversible dysfunction based on perfusion quantification in adyskinetic segments and on contractile reserve detection in hypokinetic segments was significantly more specific (83% vs 55%, p <0.00001) than standard quantitative perfusion SPECT, without major loss in sensitivity (78% vs 85%, p = NS). In conclusion, contractile reserve evaluation using dobutamine gated SPECT enhances the reliability of nitrate-enhanced sestamibi SPECT when used to predict reversible dysfunction in hypokinetic segments, whereas perfusion quantification remains superior in adyskinetic segments.

Technetium-99m sestamibi imaging to predict left ventricular ejection fraction outcome after revascularisation in patients with chronic coronary artery disease and left ventricular dysfunction: comparison between baseline and nitrate-enhanced imaging

Abstract. Acceptance of technetium-99m sestamibi as a tracer of myocardial viability is growing, particularly when nitrate-enhanced imaging is used. However, few data are available on the ability of 99mTc-sestamibi to predict the evolution of global left ventricular ejection fraction (EF). The aim of this study was to examine the ability of resting and nitrate 99mTc-sestamibi single-photon emission tomography (SPET) to predict EF changes after revascularisation in patients who have chronic coronary artery disease with left ventricular dysfunction. Using baseline resting and nitrate 99mTc-sestamibi SPET, we studied 61 patients scheduled for revascularisation because of left ventricular dysfunction. EF was estimated using two-dimensional echocardiography before and after the intervention. A post-revascularisation improvement of ≥5 EF units was defined as significant. Using a 13-segment model, 99mTc-sestamibi activity was quantified and the nitrate-induced activity changes calculated. Three different criteria for detecting viability (defined as post-revascularisation reversible dysfunction) in asynergic segments were compared: (1) resting 99mTc-sestamibi activity ≥60%; (2) nitrate 99mTc-sestamibi activity ≥65%; and (3) nitrate-induced increase >+10% or nitrate-induced increase ≤+10% and nitrate activity ≥65%. EF increased significantly in 32 patients. The number of viable asynergic segments was significantly higher in these patients than in the remaining 29 subjects, and the difference was greater (P<0.0002) using definition (3) than using either baseline (P<0.002) or nitrate activity (P<0.0005). There was a significant relationship between EF changes and number of viable asynergic segments: Spearman R=0.38, P<0.005 using baseline; Spearman R=0.39, P<0.002 using nitrate activity; and Spearman R=0.55, P<0.000005 using definition (3). According to receiver operating characteristic (ROC) curve analysis, this last criterion achieved the best results (81% sensitivity, 69% specificity and 75% accuracy), with an area under the ROC curve of 0.838; this area was significantly larger than when using either baseline (0.744, P<0.02) or nitrate activity (0.747, P<0.005). 99mTc-sestamibi SPET appears able to predict the evolution of global left ventricular EF after revascularisation, thereby confirming the value of 99mTc-sestamibi as a tracer of myocardial viability. The combination of baseline resting and nitrate imaging seems to significantly improve the diagnostic accuracy of 99mTc-sestamibi SPET for this particular purpose.

Predicting revascularization outcome in patients with coronary artery disease and left ventricular dysfunction (data from the SEMINATOR study)

A main goal of revascularization in patients with chronic ischemic cardiomyopathy is to improve global left ventricular (LV) function. This study aimed to verify whether it is possible to predict an increase in LV ejection fraction (EF) after revascularization on the basis of the extent of LV asynergy, myocardial viability, and revascularization completeness. We studied 77 patients with chronic LV ischemic dysfunction using baseline resting and nitrate-enhanced technetium-99m sestamibi single-photon emission computed tomography. Regional wall motion and global LVEF were assessed with echocardiography before and after revascularization, which was complete in 51 patients and incomplete in 26. The number of viable asynergic segments included in revascularized coronary artery territories was the strongest predictor of significant (> or = 5 EF U) functional improvement in univariate discriminant analysis. According to multivariate stepwise discriminant analysis, this parameter, together with the number of baseline asynergic segments, allowed the detection of patients with significant LVEF improvement with 75% accuracy. With use of a multivariate regression model, including the 2 mentioned variables, the measure of postrevascularization LVEF increase could be accurately quantified (R(2) 0.43, p <0.000001). In conclusion, this study suggests that the severity of baseline asynergy, the extent of myocardial viability, and the completeness of revascularization are the main determinants of postrevascularization functional recovery in patients with LV ischemic dysfunction, and that on the basis of these variables it is possible to predict the measure of LVEF increase.