Multimodality imaging and immunophenotyping of COVID-19 related myocardial injury (the MIIC-MI Study)

Abstract Background Cardiac injury is a well-recognised complication of acute COVID-19 infection, with varied aetiologies ranging from myocarditis to endothelial dysfunction, micro-embolic phenomena, and acute coronary syndromes. While persistent cardiac symptoms in patients with post-acute COVID-19 syndrome are also common, the underlying mechanisms remain unclear. A better understanding of immune-mediated drivers of chronic cardiac injury after COVID-19 infection is urgently needed to inform the management of patients with, or at risk of, long-term sequelae. Purpose To examine immune mechanisms associated with clinically detectable imaging abnormalities across a spectrum of patients with unexplained cardiac injury and/or symptoms after COVID-19 infection. Methods Participants with a history of COVID-19 infection and suspected cardiac involvement based on: a) troponin I elevation (>99th percentile upper reference limit), b) new-onset heart failure not attributable to another cause, or c) persistence of unexplained cardiac symptoms, were enrolled at a single centre in the United Kingdom between October 2020 and February 2022. Individuals with prior myocardial infarction or heart failure and those treated with immunosuppression within the past four weeks, were excluded. Cardiac magnetic resonance imaging (MRI) was performed on a 1.5T scanner following a standard clinical protocol. In parallel to cardiac imaging, peripheral blood samples were analysed for immunophenotyping using cytometry by time of flight (Fluidigm, 32 marker panel) and proteomic analysis (Olink, Target 96 Inflammation panel). Results Twenty-one patients (mean age 47 (SD 13) years, 71% female) were enrolled who had unexplained cardiac symptoms (n=17), raised troponin I (n=2), or new-onset heart failure (n=2). In total, 9/21 (43%) patients had MRI abnormalities, including a non-ischaemic pattern of late gadolinium enhancement (Figure 1a; arrow) and/or visually overt myocardial oedema on T2-weighted imaging (Figure 1b; arrow) in 8 patients, and one with impaired ventricular function in the absence of fibrosis. Patients with MRI abnormalities had higher CCL3, CCL7 (MCP-3), FGF21, and CD4 Th2 cells, and lower CD8 T effector memory cells (Figure 2, volcano plot), compared to those without. CCL7 (MCP-3) levels were correlated with native T1 mapping (r=0.45, p<0.05) and these along with CD8 T effector memory cell counts were the strongest predictors of MRI abnormalities in a LASSO regression model incorporating all clinical, cell phenotyping and proteomic data (composite AUC 0.96, CI 0.88-1). Conclusion Here we show for the first time that COVID-19 related cardiac injury in patients with MRI abnormalities is associated with increased CCL7 (MCP-3), a chemokine known to be important in viral myocarditis1, as well as decreased CD8 T effector memory cells. These findings provide novel insights into the immune-mediated mechanisms underlying non-ischemic cardiac complications of COVID-19.Fig. 1.Post-COVID imaging abnormalitiesFig. 2.Immunophenotyping and proteomics