From cytokine storm to adaptive dysregulation: temporal evolution of the inflammatory network and phase-specific intervention strategies in fulminant viral myocarditis

Fulminant viral myocarditis (FVM) is characterized by acute onset and rapid progression, often deteriorating into cardiogenic shock, malignant arrhythmias, and multi-organ failure within days. Its pathological essence does not lie in the “quantitative accumulation” of focal lymphocytic infiltration seen in ordinary myocarditis, but rather in a “qualitative shift” driven by diffuse myocardial edema compounded by a multi-cytokine cascade. Accumulating evidence indicates that the “inflection point” of myocardial injury is determined not by viral load per se, but by the dysregulated pattern recognition of viral antigens by the innate immune system and the resultant imbalance of the inflammatory network. The organising framework of this review is temporal (hyperacute to acute to reparative immune states). A spatial dimension, contrasting the circulating and the cardiac-resident immune compartments, is developed wherever direct or closely analogous data exist, but it carries far less evidence than the temporal dimension and is treated as secondary to it. Myocarditis that is immune-mediated without a replicating cardiotropic virus, including vaccine-associated and checkpoint-inhibitor disease, is used here as a labelled comparator and not as part of the entity under review. The virus invades cardiomyocytes and vascular endothelium via receptors with non-canonical distribution, subsequently triggering type I interferon responses and necroptosis through endosomal and cytosolic pattern-recognition receptors, and initiating a cascade effect via damage-associated molecular patterns (DAMPs). The driver of cardiomyocyte death does not stay constant across this course: virus-intrinsic cytopathic and ferroptotic death predominates in the first days, myeloid-mediated killing takes over through the remainder of the first week, and cytotoxic lymphocytes become the principal effectors thereafter. The hyperacute phase is characterized by macrophage phenotypic drift, neutrophil extracellular trap (NET) formation, and a “cytokine storm” whose earliest cellular sources in viral myocarditis are myeloid rather than T-cell derived. The acute phase features the “clearance-injury” paradox of cytotoxic T cells and the failure of immune checkpoint regulation, and a subset of patients may subsequently follow what the authors describe as a candidate immunoparalysis trajectory rather than an established third stage of disease - a state provisionally characterized by regulatory T cell (Treg) expansion, paradoxical elevation of interleukin-10 (IL-10), and downregulation of monocyte human leukocyte antigen-DR (HLA-DR). Its reported association with secondary infection and adverse outcome derives largely from sepsis and critical-care cohorts and has not been demonstrated in FVM. Building on this “inflammatory time window,” the authors propose a phase-specific framework intended to generate hypotheses rather than to recommend treatment: in the hyperacute phase, “fire-extinguishing” approaches (complement blockade and cytokine adsorption) may represent a potential alternative to broad-spectrum immunosuppression; in the acute phase, selective blockade of individual pathways according to inflammatory subtype may be worth exploring; and in the reparative phase, measures aimed at restoring regulatory immune capacity may be considered for study. None of these pathways, and none of the biomarker values discussed in the main text, has been prospectively validated in FVM. Finally, this review envisions individualized decision-making guided by multi-omics and dynamic immune monitoring, emphasizing that the prognosis of FVM depends on the capacity for “dynamic phenotyping and real-time switching” of immune status, rather than reliance on any single therapeutic modality.