Clonal Hematopoiesis (CHIP) in Pulmonary Embolism and CTEPH: Evidence, Mechanisms, and Risk Stratification.

Pulmonary embolism (PE) is biologically heterogeneous. Despite guideline-directed anticoagulation, a subset of patients develops recurrent venous thromboembolism, persistent exertional limitation, residual perfusion defects, and progression to chronic thromboembolic pulmonary disease (CTEPD) or chronic thromboembolic pulmonary hypertension (CTEPH). Conventional risk factors explain much of the index event but incompletely account for thrombus non-resolution and chronic sequelae. Clonal hematopoiesis of indeterminate potential (CHIP)-the age-associated expansion of hematopoietic clones carrying somatic mutations-defines a measurable thrombo-inflammatory endophenotype that is strongly genotype- and clone-size (variant allele frequency; VAF)-dependent. Across human studies, JAK2-CHIP and TET2-CHIP show the most consistent associations with VTE/PE, whereas isolated DNMT3A-CHIP is frequently neutral, and larger clones tend to confer stronger effects. Mechanistically, CHIP can bias myeloid cells toward inflammasome/IL-1β signaling and endothelial activation, increase monocyte tissue factor activity, and promote immunothrombosis with neutrophil extracellular trap (NET) formation. NET-rich thrombi may adopt a dense fibrin-DNA-histone architecture that resists endogenous fibrinolysis, favoring organization and persistence. CTEPH offers a translational window to interrogate this model because thrombotic material and deep phenotyping are accessible. We synthesize genotype- and VAF-resolved clinical and mechanistic evidence using a structured strength-of-evidence framework and propose a pragmatic phenotyping roadmap with testable predictions for prospective post-PE validation. CHIP testing in PE/CTEPH remains investigational and should not currently change standard care.