Background: The local inflammatory tissue response after acute myocardial infarction (MI) determines subsequent healing. Systemic interaction may induce neuroinflammation as a precursor to neurodegeneration.
Objectives: This study sought to assess the influence of MI on cardiac and brain inflammation using noninvasive positron emission tomography (PET) of the heart-brain axis.
Methods: After coronary artery ligation or sham surgery, mice (n = 49) underwent serial whole-body PET imaging of the mitochondrial translocator protein (TSPO) as a marker of activated macrophages and microglia. Patients after acute MI (n = 3) were also compared to healthy controls (n = 9).
Results: Infarct mice exhibited elevated myocardial TSPO signal at 1 week versus sham (percent injected dose per gram: 8.0 ± 1.6 vs. 4.8 ± 0.9; p < 0.001), localized to activated CD68+ inflammatory cells in the infarct. Early TSPO signal predicted subsequent left ventricular remodeling at 8 weeks (rpartial = -0.687; p = 0.001). In parallel, brain TSPO signal was elevated at 1 week (1.7 ± 0.2 vs. 1.4 ± 0.2 for sham; p = 0.017), localized to activated microglia. After interval decline at 4 weeks, progressive heart failure precipitated a second wave of neuroinflammation (1.8 ± 0.2; p = 0.005). TSPO was concurrently up-regulated in remote cardiomyocytes at 8 weeks (8.8 ± 1.7, p < 0.001) without inflammatory cell infiltration, suggesting mitochondrial impairment. Angiotensin-converting enzyme inhibitor treatment lowered acute inflammation in the heart (p = 0.003) and brain (p = 0.06) and improved late cardiac function (p = 0.05). Patients also demonstrated elevation of cardiac TSPO signal in the infarct territory, paralleled by neuroinflammation versus controls.
Conclusions: The brain is susceptible to acute MI and chronic heart failure. Immune activation may interconnect heart and brain dysfunction, a finding that provides a foundation for strategies to improve heart and brain outcomes.
Keywords: heart failure; inflammation; macrophages; myocardial infarction; neurodegeneration; positron emission tomography.
Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.