Patients with Ischemic Left Ventricular Dysfunction Using Low Dose Dobutamine Technetium-99m Sestamibi Gated Single-Photon Emission Computed Tomography

Abstract

The detection of viable dysfunctional myocardium is of paramount importance for clinical decision-making. Several noninvasive techniques are available to identify viable myocardium, including radionuclide imaging, echocardiography-based approaches, and magnetic resonance imaging. In the clinical setting, the most used technique is Gated Single-Photon Emission Computed Tomography (SPECT) imaging as it is cost effective. The use of 2 different markers of viability, such as cellular integrity and contractile reserve as in low dose dobutamine (LDD) gated sestamibi SPECT, showed higher predictive accuracy for reversible dysfunction than the assessment of contractile reserve only with low dose dobutamine echocardiography. Aim of the work: To predict the functional recovery in patients with ischemic left ventricular dysfunction using low dose dobutamine Technetium-99m Sestamibi gated Single-Photon Emission Computed Tomography (SPECT). Patients and methods: A Cohort of 20 consecutive patients with ischemic left cardiomyopathy was included as an exploratory pilot study. Patients with heart disease other than coronary artery disease, atrial fibrillation, peri-revascularization procedure MACE and pregnant females were excluded. All patients were subjected to a thorough history taking, clinical examination, 12 leads surface ECG and a baseline ECHO. A Timetazidine resting sestamibi Tc99 gated SPECT baseline study (protocol 1) and a low dose dobutamine sestamibi Tc99 gated SPECT study (protocol 2) were done to all patients. A 3 month follow up ECHO study was done for assessment of left ventricular EF for patients who were re-vascularized. Results: We found that myocardial perfusion data did not show any significant change during LDD infusion. LDD infusion in patients with ischemic heart disease and systolic dysfunction led to an increase in EF ≥ 5% in 30% of patients. In the re-vascularized group, post-revascularization significant (>5%) improvement in EF was found in 70% of patients. The increase in EF was accompanied by a rather significant reduction in ESV. During LDD infusion, the increase in the total number of segments with improved thickening increased the EF by 0.75% per segment, whereas the increase in the number of segments with worsened thickening reduced the EF by 1.48% per segment. With LDD infusion, the improvement in thickening of 3 severely dyskinetic segments had a significant influence on the increase in EF as compared to the less affected segments. In this study, STS in LDD Sestamibi-Tc99 Gated SPECT had an 86% Sensitivity, 67% Specificity, 86% Positive Predictive Value and 67% Negative Predictive Value for prediction of post re-vascularization global LV recovery. Whereas, positive GTI had an 86% Sensitivity, 33% Specificity, 75% Positive Predictive Value and 50% Negative Predictive Value. While, significant (≥ 5%) increase in EF during LDD SPECT; as the predictor of functional recovery; had 43% Sensitivity, 100% Specificity, 100% Positive Predictive Value and 43% Negative Predictive Value. STS and positive GTI had the best sensitivity in predicting global recovery (86%) while the best specificity (100%) was achieved by using ≥ 5% increase in LVEF during LDD infusion as the predictor of post re-vascularization global LV functional recovery. Conclusion: Contractile reserve evaluation using dobutamine Sestamibi-Tc99 Gated SPECT enhances the reliability of conventional perfusion scan in predicting post re-vascularization LV functional recovery.