{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,18]],"date-time":"2026-06-18T05:56:27Z","timestamp":1781762187863,"version":"3.54.5"},"reference-count":23,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,6,18]],"date-time":"2026-06-18T00:00:00Z","timestamp":1781740800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Med."],"abstract":"<jats:p>\n                    Heparin-induced thrombocytopenia (HIT) is a severe, prothrombotic complication of heparin therapy. While thrombocytopenia is a hallmark, diagnosis can be obscured when preceded by unexplained heparin resistance and progressive thrombosis. We present the case of a 50-year-old man with intermediate- to high-risk acute pulmonary embolism (PE), deep vein thrombosis and a right ventricular mass. Despite timely and progressive dose escalation of intravenous unfractionated heparin [UFH; up to 1,850 U\/h (~24.7 U\/kg\/h)], monitoring by activated partial thromboplastin time (APTT) revealed a failure to achieve therapeutic anticoagulation (heparin resistance), and he suffered two recurrent episodes of hemodynamic instability on treatment days 3 and 6, requiring rescue thrombolysis. Follow-up imaging revealed thrombus progression. On day 8 of heparin therapy, thrombocytopenia (platelets 104 \u00d7 10\n                    <jats:sup>9<\/jats:sup>\n                    \/L) and a high 4Ts score (6 points) prompted HIT suspicion. Heparin was immediately discontinued and replaced with intravenous argatroban (initiated at 2 \u03bcg\/kg\/min), resulting in prompt attainment of the target therapeutic APTT range. HIT was confirmed by positive anti-platelet factor 4 (PF4)\/heparin immunoglobulin G (IgG) antibodies. After platelet count recovery (to &amp;gt;150 \u00d7 10\n                    <jats:sup>9<\/jats:sup>\n                    \/L), argatroban was discontinued and anticoagulation was switched to oral rivaroxaban. Follow-up studies at discharge and 3 months showed significant thrombus resolution, with normalized cardiac function and complete resolution of the intracardiac mass. This case underscores that unexplained heparin resistance with thrombotic progression, even preceding significant thrombocytopenia, a recognized harbinger of HIT-associated thrombosis, is a critical indicator of HIT. Immediate diagnostic evaluation and switch to non-heparin anticoagulants are imperative to avert life-threatening complications.\n                  <\/jats:p>","DOI":"10.3389\/fmed.2026.1818171","type":"journal-article","created":{"date-parts":[[2026,6,18]],"date-time":"2026-06-18T05:36:32Z","timestamp":1781760992000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Case Report: Heparin resistance as the harbinger of heparin-induced thrombocytopenia in acute pulmonary embolism"],"prefix":"10.3389","volume":"13","author":[{"given":"Na","family":"Yu","sequence":"first","affiliation":[{"name":"Department of Pulmonary and Critical Care Medicine, Liaocheng People's Hospital, Liaocheng","place":["Shandong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fengqiang","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Pulmonary and Critical Care Medicine, Liaocheng People's 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