Platelet Tissue Factor Pathway Inhibitor-Α Dampens Cardiac Thrombosis and Associated Fibrosis in Mice.

•Tissue factor pathway inhibitor α (TFPIα) is the only TFPI isoform in platelets (pltTFPIα) and inhibits prothrombinase.•Mice differing in the presence or absence of pltTFPIα and lacking other TFPIs were produced.•Mice without pltTFPIα developed cardiac thrombi and severe cardiac fibrosis.•Platelets promoted cardiac fibrosis after irradiation in a manner modulated by pltTFPIα.