Residual post-infarct myocardial inflammation detected by 68Ga-DOTATATE PET/MRI predicts long-term adverse cardiac remodelling

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Abstract Background Maladaptive inflammatory responses are associated with adverse cardiac remodelling after myocardial infarction (MI), but clinical methods for detecting residual myocardial inflammation post-MI are lacking. Purpose To investigate somatostatin receptor subtype 2 (SST2) positron emission tomography (PET)/magnetic resonance imaging (MRI) using 68Ga-DOTATATE after MI. Methods In a prospective observational cohort study, infarct-related myocardial inflammation detected by 68Ga-DOTATATE PET at 2wk and 3mo post-MI was compared with MRI characteristics including left ventricular (LV) volumetric changes at 1yr, as well circulating immune cell phenotyping and serum proteomic markers. Patients with a prior history of MI or heart failure were excluded. Histological SST2 expression was assessed in myocardial biopsies. Results 38 participants (mean age 60 [SD 9] years; 84% male) with recent MI were enrolled, of whom 58% had an ST-segment elevation MI. Mean peak Troponin I was 16,665 (range 408 to >25,000) ng/L and mean post-infarct LV ejection fraction was 51 (SD 9) %. 68Ga-DOTATATE maximum standardized uptake values (SUVmax) at 10 (SD 4) days accurately localised infarcted myocardial segments defined by late-gadolinium enhancement MRI (LGE; Fig. 1); were 14.2% higher in akinetic/hypokinetic vs. normo-kinetic segments (p<0.0001); and were correlated both with peak segmental strain (r=0.47, p=0.003) and segmental T1 values (r=0.51, p=0.02). Mean infarct SUVmax was 19.7% lower on repeat PET/MRI after a mean 102 (SD 22) days (p<0.0001), and this change was in keeping with parallel reductions in T2-weighted oedema signal on MRI and serum biomarkers of cardiac injury and systemic inflammation. Residual inflammation assessed by mean infarct SUVmax at 3mo was correlated with ΔLV indexed end-diastolic volume at 369 (SD 14) days, after adjustment for baseline infarct size and other clinical variables (p=0.038). The 3mo:2wk ratio of mean infarct SUVmax was an even stronger predictor of adverse myocardial remodelling (p=0.0025). Circulating SST2+ classical monocytes were correlated with infarct 68Ga-DOTATATE signal (r=0.47, p=0.02), and SST2 was co-expressed with CD68+ macrophages in inflamed myocardial specimens of patients with recent MI and ischaemic heart failure. After statistical feature selection and multiple comparisons adjustments, among the blood markers associated with 3mo:2wk infarct SUVmax was CCL25, a chemokine involved in macrophage recruitment which has been implicated in adverse cardiac remodelling. Conclusions Here, in the first prospective clinical study of serial SST2 PET/MRI after MI, we show that 68Ga-DOTATATE can identify and track resolving infarct-related myocardial inflammation. Moreover, residual inflammation detected by 68Ga-DOTATATE is associated with long-term adverse myocardial remodelling and could provide a potential future imaging biomarker to help stratify high-risk patients for emerging immunomodulatory therapies.Figure 1.68Ga-DOTATATE PET-MRI after MI