PVT can be classified into obstructive and nonobstructive forms, which differ in clinical presentation, hemodynamic impact, and management implications. Obstructive PVT is characterized by impaired leaflet mobility, leading to elevated transvalvular gradients, progressive heart failure, and, in severe cases, cardiogenic shock. nonobstructive PVT, in contrast, may present subclinical or with minor hemodynamic changes but carries a significant risk of thromboembolic events, including stroke and systemic embolization. ^,

The degree of obstruction correlates with thrombus size, mobility, and location relative to the valve structure. Obstruction is most often encountered with mechanical mitral valves due to lower flow velocities, whereas nonobstructive thrombi are more commonly reported in the aortic position, where higher flow rates partially limit thrombus growth.

Several patient-, valve-, and treatment-related factors contribute to PVT risk:

• a.

  Valve Type and Design: Mechanical valves, especially older generation bileaflet and caged-disk prostheses, carry a higher thrombogenic potential than modern bioprostheses. Valve position also matters: mitral mechanical valves are most prone to thrombosis, followed by tricuspid and aortic valves.

• b.

  Suboptimal Anticoagulation: Suboptimal anticoagulation with vitamin K antagonists (VKAs) is a major contributor to mechanical PVT. This encompasses any circumstance in which anticoagulant therapy fails to provide adequate thromboembolic protection, most commonly due to a subtherapeutic international normalized ratio (INR) resulting from inadequate prevention of PVT.

• c.

  Patient-Specific Factors: Genetic thrombophilias, atrial fibrillation, left atrial enlargement, and prior thromboembolism are strong predictors of PVT. Additional comorbidities such as renal failure, diabetes, and systemic inflammatory conditions may further amplify thrombotic risk. ^,,

• d.

  Hemodynamic and Structural Considerations: Left atrial stasis, atrial appendage thrombi, and suboptimal valve seating contribute to thrombus formation. Postoperative endothelial injury and local turbulence at the prosthesis surface may initiate thrombogenesis.

Thrombus formation in PVT reflects the classical Virchow’s triad—stasis, endothelial injury, and hypercoagulability—exacerbated by disrupted laminar flow over prosthetic surfaces. Activated platelets, fibrin deposition, and local inflammation contribute to thrombus growth and adherence, increasing obstruction and embolic risk. nonobstructive thrombi may remain small and mobile, often incidentally detected, but still carry embolic potential. These mechanistic insights guide anticoagulation and thrombolytic strategies ( Figure 1 ).

Pathophysiological mechanisms driving prosthetic valve thrombosis. (A) Clinical context of a patient with a mechanical mitral valve prosthesis. (B) Central determinants of prosthetic valve thrombogenesis, integrating valve-related, patient-related, and blood-related contributors. 1) Mechanical prosthesis–associated flow disturbances combined with absent or suboptimal oral anticoagulation promote hemodynamic shear abnormalities, stasis, and activation of surface-dependent coagulation pathways. 2) Patient-related risk factors— Atrial fibrillation, left atrial enlargement, and reduced left ventricular ejection fraction—further amplify blood stasis and atrial prothrombotic remodeling, facilitating thrombin generation. 3) Blood-related prothrombotic factors, including coagulation disorders, hematologic abnormalities, and inherited thrombophilias, enhance fibrin formation and clot propagation. Together, these mechanisms converge on excessive thrombin production, fibrin deposition, and organization of prosthetic valve thrombus. C) Final manifestation: obstructive thrombus adherent to the mechanical mitral prosthesis, impairing leaflet mobility and increasing left atrial pressure. Created in BioRender® by Lacerda, RAV. (2025).

The pathophysiologic distinction between obstructive and nonobstructive PVT informs diagnosis, risk stratification, and therapy. Obstructive PVT typically necessitates urgent intervention due to rapid hemodynamic compromise, whereas nonobstructive PVT allows for careful assessment of thrombus characteristics, embolic risk, and patient comorbidities before selecting an optimal therapeutic strategy. ^,

Prevention remains central to PVT management. VKAs, primarily warfarin, continue to be the standard of care for thromboprophylaxis in patients with mechanical heart valves. Maintaining an adequate level of anticoagulation is critical, as subtherapeutic anticoagulation represents the most important modifiable risk factor for PVT. Time in therapeutic range (TTR) greater than 65–70% has been consistently associated with a lower risk of thrombotic complications.

Structured anticoagulation management through dedicated anticoagulation clinics has been shown to improve TTR, reduce thrombotic and bleeding complications, and enhance patient adherence. Patient education, regular monitoring, and the use of home INR self-testing devices may further improve anticoagulation quality and clinical outcomes.

Direct oral anticoagulants (DOACs) are contraindicated in patients with mechanical heart valves, as demonstrated in the RE-ALIGN trial, which showed increased rates of thromboembolic and bleeding complications compared with warfarin. Therefore, VKAs remain the only recommended oral anticoagulants in this population.

Bridging anticoagulation with unfractionated heparin or low-molecular-weight heparin (LWMH) is recommended during temporary interruptions of warfarin therapy, particularly in high-risk patients, to minimize thrombosis risk. Prevention strategies should also address patient-related and prosthesis-related risk factors, including atrial fibrillation, left ventricular dysfunction, hypercoagulable states, and suboptimal anticoagulation adherence.

PVT exhibits a spectrum of clinical manifestations, ranging from asymptomatic to life-threatening. Obstructive PVT often presents with acute dyspnea, fatigue, pulmonary edema, hypotension, or cardiogenic shock, reflecting sudden increases in transvalvular gradients and impaired cardiac output. nonobstructive PVT may be silent or present subtly with minor dyspnea, palpitations, or systemic embolic events such as stroke, transient ischemic attack, or peripheral arterial occlusion.

Physical examination may reveal classic signs of prosthetic valve dysfunction. In obstructive mitral PVT, auscultation may detect a diminished or absent mechanical click and a new loud mitral regurgitation murmur. In aortic valve obstruction, changes in systolic murmur intensity or new diastolic murmurs may be noted. Heart failure signs—including pulmonary rales, jugular venous distension, and peripheral edema—are common in advanced obstruction. ^,

Echocardiography is the cornerstone of PVT diagnosis. Transthoracic echocardiography (TTE) provides initial assessment, identifying elevated transvalvular gradients, reduced leaflet motion, and indirect evidence of thrombus. However, its sensitivity for small thrombi is limited, especially in obese patients or those with prostheses causing acoustic shadowing.

Transesophageal echocardiography (TEE) offers superior spatial resolution and sensitivity, particularly for nonobstructive thrombi and left atrial appendage evaluation. TEE can distinguish thrombus from pannus formation, prosthetic vegetations, or other masses by assessing mobility, echogenicity, and attachment site. Real-time 3-dimensional TEE further enhances visualization, aiding in precise thrombus measurement and surgical planning. ^,,

Fluoroscopy remains valuable for mechanical prostheses, allowing direct observation of leaflet or disc motion. Restricted opening angles or delayed closure times strongly suggest obstructive thrombosis. Fluoroscopy is rapid, noninvasive, and complementary to echocardiography, particularly when acoustic windows are suboptimal. ^,

Multidetector computed tomography (MDCT) provides high-resolution anatomic imaging, differentiating thrombus from pannus by density and enhancement patterns. MDCT is particularly useful for complex aortic prostheses and for patients with contraindications to TEE. Cardiac magnetic resonance imaging (MRI) is less commonly used due to device artifact concerns but can be considered for selected bioprosthetic cases.

Laboratory evaluation is supportive but not diagnostic. Subtherapeutic anticoagulation (low INR in patients receiving VKAs is frequently observed and represents a major predisposing factor for PVT.

Several circulating biomarkers may refine thrombotic risk stratification in PVT, reflecting inflammation, platelet activation, hemostasis, and genetic susceptibility. Hematologic indices (Red Cell Distribution Width/Platelets, Monocyte-to-HDL Cholesterol Ratio) show potential but require larger validation. Thrombophilia variants (Prothrombin Gene Mutation, Human Platelet Antigen‑1, GPIIIa T196C polymorphism, Methylenetetrahydrofolate Reductase A1298C) and platelet hyperreactivity have been associated with obstructive PVT. d -dimer and Brain natriuretic peptide correlate with thrombus burden and hemodynamic impact. ^,, While informative, most evidence derives from small or retrospective cohorts, necessitating further multicenter validation.

Accurate diagnosis of PVT requires a comprehensive multimodal approach integrating clinical evaluation, laboratory biomarkers, and advanced imaging. Clinical history and physical findings raise initial suspicion, while laboratory data, including anticoagulation status and selected inflammatory and hemostatic markers provide complementary information on thrombotic risk and activity.

Imaging is central to diagnosis: TEE enables detailed assessment of thrombus size, mobility, and hemodynamic impact, whereas computed tomography further characterizes lesion density and morphology. ^, Despite advances in multimodal imaging, differentiation between thrombus and pannus remains challenging in some cases, particularly when both processes coexist. Echocardiographic features such as mobility and echogenicity, as well as computed tomography attenuation characteristics, improve diagnostic accuracy but do not provide absolute certainty.

This residual diagnostic uncertainty has important therapeutic implications, as thrombolysis is effective for thrombus but ineffective for pannus, and inappropriate treatment selection may delay definitive intervention. In such borderline cases, individualized decision-making incorporating imaging findings, clinical presentation, anticoagulation status, and institutional expertise remains essential.

Surgery has traditionally been the definitive treatment for PVT, particularly in patients with severe obstruction or hemodynamic instability. It provides immediate thrombus removal and restoration of valve function, preventing complications such as cardiogenic shock and systemic embolization. ^,

Advances in cardiopulmonary bypass, myocardial protection, and perioperative care have improved outcomes. Contemporary series report operative mortality of 5–15% for urgent procedures, depending on valve position, comorbidities, and clinical status at presentation. ^, Long-term outcomes are generally favorable in experienced centers, with five-year survival exceeding 70% to 80%, although recurrent thrombosis remains a concern, especially with suboptimal anticoagulation or thrombogenic valve designs.

However, surgery carries significant risks. Emergency procedures have higher mortality than elective interventions, and complications, including bleeding, infection, prosthetic dysfunction, and cerebrovascular events remain relevant. Careful patient selection is essential, balancing hemodynamic severity, operative risk, comorbidities, and institutional expertise. ^,,

TT has emerged as an effective alternative to surgery, particularly in patients at high operative risk or with contraindications to surgery. Early experience raised concerns regarding safety, but subsequent studies demonstrated that carefully monitored TT can restore valve function without immediate surgical intervention.

High rates of valve opening recovery have been reported with intravenous thrombolysis in mechanical PVT, particularly in patients with smaller thrombus burden and minimal pannus formation, as demonstrated by Özkan et al. using serial TEE monitoring. Similarly, Lengyel and Vandor reported successful outcomes in most patients, emphasizing the importance of individualized treatment and careful monitoring.

Larger series confirmed these findings. Roudaut et al. reported 127 cases of mechanical PVT treated with thrombolysis, with complete resolution in 71%, partial resolution in 17%, and no improvement in 12%. Although embolic and hemorrhagic complications occurred, thrombolysis was effective in most cases, supporting its use in selected patients or when surgery is unavailable.

In a single-center series of 68 patients treated with streptokinase as first-line therapy, valve opening was achieved in a high proportion of cases with low complication and mortality rates. Predictors of success include smaller thrombus size and less severe obstruction, whereas delayed treatment and extensive thrombus burden increase complication risk.

Tenecteplase has recently emerged as a promising alternative thrombolytic agent. Compared with alteplase, it offers greater fibrin specificity, longer half-life, and bolus administration. In the TENET Randomized Clinical Trial (TENET), tenecteplase achieved higher complete success rates than slow-infusion alteplase (97.5% vs 81.5%) without increased complications and was associated with shorter hospital stay, supporting its potential role in PVT management.

Collectively, these studies demonstrate that TT is an effective and viable treatment strategy. Optimal outcomes depend on careful patient selection, individualized dosing, and continuous imaging monitoring. TT is particularly valuable in high-risk surgical patients or when surgery is unavailable.

Comparative studies provide important insights into efficacy and safety. Both surgery and thrombolysis effectively restore valve function, but their risk profiles differ, requiring individualized treatment.

Early studies, including Roudaut et al., demonstrated that surgery provides immediate mechanical correction, particularly in severe obstruction, while thrombolysis offers a less invasive alternative with acceptable success rates, especially in high-risk patients. Huang et al. emphasized the importance of thrombus size, hemodynamic status, and institutional experience in treatment selection.

Meta-analyses further clarify outcomes. Karthikeyan et al. reported similar survival between surgery and thrombolysis, with higher perioperative complications in surgical patients and increased embolic risk with thrombolysis. Castilho et al. found lower mortality with thrombolysis (6.6% vs 18.1%) but higher embolic events (12.8% vs 4.6%), while overall success rates were similar.

The Multicenter HATTUSHA Study (HATTUSHA) demonstrated that slow and ultraslow thrombolytic regimens achieve high success rates, low mortality, and acceptable complication rates, with outcomes comparable to surgery in selected patients.

Similarly, Chopard et al., in a meta-analysis of 1,389 patients, reported lower mortality with thrombolysis (10.8% vs 15.3%), although embolic events were more frequent. Treatment success and major complications were comparable between groups, supporting thrombolysis as a first-line option in selected patients without cardiogenic shock.

The first randomized trial comparing urgent surgery with slow-infusion tPA showed similar efficacy but higher complication rates with surgery, including increased mortality and major adverse events. These findings support thrombolysis as an effective and potentially safer alternative in selected patients.

Overall, both surgery and thrombolysis are effective treatments. Selection should be guided by hemodynamic status, thrombus characteristics, comorbidities, and institutional expertise. Thrombolysis, particularly with slow or ultraslow low-dose protocols, is increasingly recognized as first-line therapy in selected patients, whereas surgery remains essential for severe obstruction, large thrombi, or thrombolysis failure.