Combining FDG-PET and 99mTc-SPECT to predict functional outcome after coronary artery bypass surgery

Single-photon emission computed tomography (SPECT) and positron emission tomography (PET) are suggested to improve clinical decision-making in ischaemic cardiomyopathy. Here, we present a unique cohort of patients who underwent nuclear medicine studies and cardiac magnetic resonance imaging (MRI) both before and 1 year after coronary artery bypass (CABG) surgery to assess benefit from surgery.

Before CABG, we applied three quantitative techniques using (18)F-fluorodeoxyglucose-PET and (99m)technetium-tetrofosmin-SPECT with a software tool to measure defects with hypoperfused but viable and non-viable myocardium in 15 patients. One method used solely PET, two others combined PET and SPECT at different thresholds. As a reference, we used change in left-ventricular (LV) function and volume by MRI. Preoperatively, ischaemic but viable areas detected by the method with a 10% threshold combining PET-SPECT and the PET-only method correlated significantly with preoperative regional wall thickening (WT; P = 0.03 and P = 0.005, respectively). When compared with global functional outcome (change in LV ejection fraction) and LV remodelling (change in end-diastolic volume) 1 year postoperatively, no correlation appeared with preoperative PET- or PET-SPECT-derived viable or non-viable tissue. Neither was any correlation observable between local change in WT and local preoperative defect size evaluated by any of these three methods.

Preoperatively, PET and PET-SPECT with 10% threshold detected dysfunctional myocardium, but all analysis methods failed to predict 1-year functional outcome assessed by MRI. In patients with three-vessel disease and heart failure, SPECT perfusion and PET viability study results show substantial heterogeneity; this should be considered when selecting patients for revascularization.