¹⁸F-FDG uptake in postischemic myocardium: relevance as a prognostic marker for functional recovery

Objectives Inflammation in postischemic myocardium has been proposed as an important factor for cardiac remodeling after myocardial infarction(MI). Recent clinical studies used FDG PET/MRI for noninvasive quantification of these inflammatory processes. We report for the first time on the significance of myocardial FDG uptake post-MI as a novel biosignal for LV functional recovery.

Methods 32 patients with acute MI were prospectively enrolled and imaged 4.9±1.3 days after PCI using FDG PET/MRI. Unspecific myocardial uptake was suppressed by a low-carbohydrate,high-fat diet and by heparin administration before FDG injection. FDG uptake in postischemic myocardium was quantified as mean SUV normalized to the lean body mass(SUV). The cellular innate immune response was assessed repeatedly during the first week after MI. At the time of submission,22 subjects were followed up by MRI 237±58 days after PCI.

Results SUV in postischemic myocardium was 2.1±0.5 in all patients as well as in the follow-up subgroup. Infarct size in the follow-up group was 27±12 %LV. The EF decreased from 50±8% to 46±10% (p<0.008),and the ESV increased from 59±20 ml to 68±23 ml (p<0.02). No differences were observed for EDV (117±27 ml vs. 124±26 ml, p=NS) and SV (58±12 ml vs. 56±13 ml,p=NS). However,ΔEF (-5±7%) showed a inverse correlation with SUV (R=-0.53,p<0.02). Furthermore,there was a positive correlation between SUV and ΔESV (10±16 ml; R=0.62,p<0.003) and ΔEDV (8±21 ml; R=0.46,p<0.04). Also,ΔESV correlated with peak leukocyte count (12.4±2.8 G/l; R=0.45,p<0.04) and ΔSV was linked to peak count of inflammatory monocytes (0.7±0.2 G/l; R=0.53,p<0.02). Infarct size,pain-to-balloon-time and peak counts of intermediate or reparative monocytes did not correlate with ΔEF,ΔEDV or ΔESV.

Conclusions FDG uptake in postischemic myocardium after MI is negatively correlated with LV functional recovery independently from infarct size and pain-to-balloon-time. However,if the myocardial FDG signal truly reflects post-MI inflammation still needs to be elucidated.