An Unusual Case of Massive Prosthetic Aortic Valve Thrombosis in a Hypocoagulated Patient

Abstract

Background: Prosthetic valve thrombosis (PVT) is a rare but life-threatening complication of mechanical valve replacement, with an estimated incidence of 0.5–6% per patient-year, depending on valve position and anticoagulation adequacy (Dangas et al., 2016). While thrombus formation is the primary mechanism, pannus (fibrotic tissue ingrowth) coexists in up to 30% of obstructive PVT cases, complicating diagnosis and management (Deviri et al., 1991; Ha et al., 2018). Clinical presentation ranges from incidental findings to fulminant cardiogenic shock, with mortality exceeding 50% in obstructive left-sided PVT without prompt intervention (Cáceres-Lóriga et al., 2006). Diagnosis relies on multimodal imaging, primarily transthoracic echocardiography (TTE) and cinefluoroscopy. Current guidelines prioritize emergency surgery for hemodynamically unstable patients, while fibrinolysis is reserved for high-surgical-risk cases or resource-limited settings (Otto et al., 2021). Case Presentation: A 34-year-old woman with a history of rheumatic heart disease (diagnosed at age 12) and subsequent mechanical aortic (19-mm St. Jude) and mitral (27-mm St. Jude) valve replacement at age 28 presented with acute pulmonary edema and cardiogenic shock. She reported a 2-week history of progressive dyspnea, hemoptysis, and macroscopic hematuria. Postoperative anticoagulation with Acenocoumarol (4 mg/day) was initiated for thromboembolism prophylaxis. However, the patient demonstrated poor adherence over the past year, and despite self-reported adherence in the preceding month, her admission INR was paradoxically elevated to 6.5. Physical examination revealed hypotension (85/46 mmHg), tachycardia (112 bpm), bilateral rales, and new murmurs of aortic stenosis and regurgitation. Transthoracic echocardiography (TTE) demonstrated severe prosthetic aortic valve obstruction (mean gradient: 98 mmHg; effective orifice area: 0.3 cm²) with concomitant severe regurgitation. Cinefluoroscopy confirmed prosthetic valve thrombosis (PVT), showing leaflets immobilized in a semi-open position (opening angle <10°). Emergency redo aortic valve replacement revealed mixed fresh thrombus and circumferential pannus obstructing the prosthesis; the mitral valve remained patent. Conclusion: This case highlights the paradox of life-threatening prosthetic valve thrombosis despite supratherapeutic anticoagulation, underscoring the roles of pannus formation and turbulent flow in small-valve prostheses. It reinforces that PVT requires urgent multimodal imaging and emergent intervention, even in anticoagulated patients, and emphasizes stricter adherence monitoring.