The immune system orchestrates the repair of infarcted myocardium. Imaging of the cellular inflammatory response by ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/magnetic resonance imaging in the heart has been demonstrated in preclinical and clinical studies. However, the clinical relevance of post-MI ¹⁸F-FDG uptake in the heart has not been elucidated. The objective of this study was to explore the value of ¹⁸F-FDG positron emission tomography/magnetic resonance imaging in patients after acute myocardial infarction as a biosignal for left ventricular functional outcome.

We prospectively enrolled 49 patients with ST-segment–elevation myocardial infarction and performed ¹⁸F-FDG positron emission tomography/magnetic resonance imaging 5 days after percutaneous coronary intervention and follow-up cardiac magnetic resonance imaging after 6 to 9 months. In a subset of patients, ^99mTc-sestamibi single-photon emission computed tomography was performed with tracer injection before revascularization. Cellular innate immune response was analyzed at multiple time points. Segmental comparison of ¹⁸F-FDG-uptake and late gadolinium enhancement showed substantial overlap (κ=0.66), whereas quantitative analysis demonstrated that ¹⁸F-FDG extent exceeded late gadolinium enhancement extent (33.2±16.2% left ventricular myocardium versus 20.4±10.6% left ventricular myocardium, P<0.0001) and corresponded to the area at risk (r=0.87, P<0.0001). The peripheral blood count of CD14^high/CD16⁺ monocytes correlated with the infarction size and ¹⁸F-FDG signal extent (r=0.53, P<0.002 and r=0.42, P<0.02, respectively). ¹⁸F-FDG uptake in the infarcted myocardium was highest in areas with transmural scar, and the standardized uptake value_mean was associated with left ventricular functional outcome independent of infarct size (Δ ejection fraction: P<0.04, Δ end-diastolic volume: P<0.02, Δ end-systolic volume: P<0.005).

In this study, the intensity of ¹⁸F-FDG uptake in the myocardium after acute myocardial infarction correlated inversely with functional outcome at 6 months. Thus, ¹⁸F-FDG uptake in infarcted myocardium may represent a novel biosignal of myocardial injury.