Management of mechanical prosthetic valve thrombosis and obstruction

INTRODUCTION — Replacement of a diseased heart valve with a prosthetic heart valve exchanges the native disease for prosthesis-related complications [1,2]. Complications include prosthetic valve obstruction (including thrombosis and pannus formation), embolic events, bleeding, prosthetic heart valve regurgitation (valvular and paravalvular), infective endocarditis, and prosthetic valve-related hemolysis.

The management of mechanical prosthetic valve thrombosis (PVT) and obstruction are reviewed here. Related issues including clinical manifestations, initial evaluation and diagnosis of mechanical valve PVT and obstruction as well as diagnosis and management of bioprosthetic valve obstruction and thrombosis are reviewed separately:

●(See "Bioprosthetic valve thrombosis, thromboembolism, and obstruction: Clinical manifestations and diagnosis".)

●(See "Mechanical prosthetic valve thrombosis or obstruction: Clinical manifestations and diagnosis".)

●(See "Bioprosthetic valve thrombosis, thromboembolism, and obstruction: Management".)

Management of mechanical valve obstruction and thrombosis during pregnancy differs from the approach presented here, as discussed separately. (See "Management of risks of prosthetic valves during pregnancy", section on 'Risks associated with prosthetic valves'.)

KEY CONSIDERATIONS

Management based upon diagnosis — Management of mechanical prosthetic valve obstruction or thrombosis is based upon the clinical presentation (eg, symptoms and signs of heart failure) and the cause of obstruction, if present. Thrombus forming on a mechanical prosthetic valve can be nonobstructive or obstructive and either may cause thromboembolic events [3-6]. Mechanical prosthetic valve obstruction may be caused by thrombus or pannus formation. The evaluation of mechanical prosthetic valve obstruction focuses on distinguishing these two causes since thrombus may be treated by anticoagulation, thrombolysis, or valve surgery (thrombectomy or repeat valve replacement), while pannus can be treated only by valve surgery. (See "Mechanical prosthetic valve thrombosis or obstruction: Clinical manifestations and diagnosis".)

Infectious endocarditis is an uncommon cause of valve obstruction that should be considered during the diagnostic evaluation and treated as appropriate. (See "Prosthetic valve endocarditis: Epidemiology, clinical manifestations, and diagnosis" and "Antimicrobial therapy of prosthetic valve endocarditis" and "Surgery for prosthetic valve endocarditis".)

Individualized assessment of treatment options — For patients with prosthetic valve obstruction with an indication for valve surgery or fibrinolysis, we recommend referral to a Heart Valve Team for individualized assessment of the risks and benefits of surgery and fibrinolysis.

The Heart Valve Team performs an individualized assessment of potential risks and benefits including consideration of the following factors as outlined in the 2020 American College of Cardiology/American Heart Association valve guidelines [2]:

●The following factors favor fibrinolysis (see 'Fibrinolytic therapy' below):

•Clinical features – High surgical risk, New York Heart Association (NYHA) functional class I to III, no contraindication to fibrinolysis, first-time episode of valve thrombosis.

•Concurrent indications – No need for other cardiac surgery such as coronary artery bypass graft (CABG) surgery or other valve or aortic disease.

•Imaging findings – Presence of mass consistent with thrombus, small clot (≤0.8 cm²), no left atrial thrombus.

•Resources – No surgical expertise available.

●The following factors favor surgery (see 'Surgery' below):

•Clinical features – Low surgical risk, NYHA functional class IV, contraindication to fibrinolysis, recurrent valve thrombosis.

•Imaging features – Possible or suspected pannus, large clot (>0.8 cm²), or left atrial thrombus.

•Concurrent indications – Coronary artery disease requiring CABG surgery, concomitant valve or aortic disease requiring surgery.

•Resources – Available surgical expertise.

●For patients with an indication for surgery, but with clinical features that suggest quality of life is not expected to improve with surgery or life expectancy with surgery of ≤1 year, palliative care consultation is suggested to determine the best management plan. (See "Overview of comprehensive patient assessment in palliative care".)

URGENT MANAGEMENT OF MECHANICAL VALVE OBSTRUCTION — Urgent management of moderately to severely symptomatic (New York Heart Association [NYHA] functional class III or IV) mechanical valve obstruction or high-risk left-sided valve thrombus (ie, a mobile thrombus >0.3 cm in diameter or any thrombus with area ≥0.8 cm²) includes temporizing supportive medical care and urgent Heart Valve Team assessment to guide further care.

Temporizing medical care — Temporizing supportive medical care for moderately to severely symptomatic mechanical valve obstruction includes respiratory support as needed, cautious treatment of hypertension, and treatment of heart failure with cautious use of diuretics to treat volume overload. If the international normalized ratio (INR) is subtherapeutic, anticoagulation with unfractionated heparin (UFH) is instituted. Medical therapies such as diuretics and antihypertensive agents pose the risk of destabilizing the patient with symptomatic prosthetic valve obstruction. (See 'Medical therapy for heart failure' below.)

Urgent Heart Valve Team assessment — Patients with mechanical valve obstruction causing moderate to severe symptoms (NYHA functional class III or IV) or high-risk left-sided valve thrombus (a mobile thrombus >0.3 cm in diameter or any thrombus with area ≥0.8 cm²) require urgent referral to a Heart Valve Team for an individualized assessment of risks and benefits to guide the choice between valve surgery and fibrinolytic therapy (if thrombus is suspected). The urgency of treatment depends upon the acuity and severity of the patient’s symptoms. (See 'Individualized assessment of treatment options' above.)

Recommendations for urgent therapy — The presumptive cause of mechanical valve obstruction guides the therapeutic choices (see 'Individualized assessment of treatment options' above):

●Urgent therapy for presumptive thrombosis

•Patients with obstructive, left-sided mechanical valve thrombosis causing NYHA class IV symptoms or hemodynamic instability require urgent intervention. While slow-infusion, low-dose fibrinolytic regiments have significantly improved the hemodynamic success rates and pose a relatively low risk of complications, the existing protocols may still take too long for a clinical response in critically ill patients and may increase the risk of rescue surgical intervention. For most of these patients, we therefore suggest surgery rather than fibrinolysis. (See 'Surgery' below and 'Fibrinolytic therapy' below.)

The urgency of surgery is based upon the acuity and severity of patient symptoms. Prior to surgery, the patient is treated with intravenous UFH with goal activated partial thromboplastin time (aPTT) of 2 to 2.5 times control.

•Patients with left-sided mechanical valve thrombosis (obstructive or nonobstructive) with a mobile thrombus ≥0.3 cm in diameter or a large nonmobile thrombus (≥0.8 cm²) require urgent intervention. For most of these patients, we suggest surgery rather than fibrinolysis. (See 'Surgery' below and 'Fibrinolytic therapy' below.)

●Urgent therapy for presumptive pannus – For patients with clinical and imaging features consistent with prosthetic valve pannus with moderately to severely symptomatic obstruction, the treatment options are surgery or palliative care. The considerations above guide the choice between these options. (See 'Individualized assessment of treatment options' above and 'Surgery' below.)

●Urgent therapy for presumptive thrombosis plus pannus – For patients with clinical and imaging features consistent with PVT with moderately to severely symptomatic obstruction, the treatment options are fibrinolysis or surgery. Surgery is generally preferred in this setting since fibrinolysis is unlikely to resolve the obstruction. In this setting, fibrinolysis is an option only for hemodynamically stable patients who have clear evidence of predominant thrombus. (See 'Individualized assessment of treatment options' above and 'Components of therapy' below.)

NONURGENT MANAGEMENT — For patients presenting with class I to III symptoms, we suggest the following approach.

For valve obstruction — For patients with prosthetic valve obstruction with New York Heart Association (NYHA) functional class I to III, management is aimed at prompt control of symptoms and treatment of the cause of obstruction (eg, thrombus or pannus).

●Medical treatment of symptomatic heart failure with cautious use of diuretics and other medical therapy (eg, angiotensin converting enzyme inhibitor), given risk of destabilization with attempted therapy. (See 'Medical therapy for heart failure' below.)

●Treatment of obstruction depends upon the presumptive cause and the valve location (left- or right-sided):

•For patients with obstructive, left-sided mechanical PVT with NYHA functional class I to III and a small thrombus (nonmobile and <0.8 cm² or mobile and ≤0.3 cm in diameter), we suggest a trial of therapeutic anticoagulation with intravenous (IV) unfractionated heparin (UFH) for several (eg, five to seven) days with goal activated partial thromboplastin time (aPTT) 2 to 2.5 times control; aspirin 75 to 100 mg daily is continued during this therapy. (See 'Optimized antithrombotic therapy' below.)

Follow-up transesophageal echocardiography is performed to assess thrombus resolution or progression and assess valve function.

If thrombus persists, we suggest fibrinolytic therapy. (See 'Fibrinolytic therapy' below.)

•For patients with left-sided obstructive mechanical PVT with persistent NYHA class II (or greater symptoms) despite fibrinolysis (see 'Fibrinolytic therapy' below) or with an absolute contraindication to fibrinolytic therapy, we suggest valve surgery. (See 'Surgery' below.)

•For patients with obstructive right-sided mechanical PVT, we suggest fibrinolytic therapy. Aspirin 75 to 100 mg daily is continued, and vitamin K antagonist (VKA) is held during this therapy. (See 'Fibrinolytic therapy' below.)

•For patients with symptomatic severe mechanical prosthetic valve obstruction not caused by thrombus (eg, pannus), we recommend referral to a Heart Valve Team for an individualized assessment of the risk/benefit of valve surgery or palliative care. For operable patients with symptomatic severe mechanical prosthetic heart valve stenosis not caused by thrombus, we recommend repeat surgical valve replacement or thrombectomy. (See 'Surgery' below.)

•When imaging findings are indeterminate for thrombus or pannus, management is generally as for pannus unless clinical features are strongly suggestive of thrombus as the predominant cause of obstruction.

For valve thrombosis without obstruction — For patients with mechanical valve PVT without obstruction, treatment is aimed at thrombus resolution.

●For patients with left- or right-sided mechanical PVT with a small thrombus (nonmobile and <0.8 cm² or mobile and <0.3 cm in diameter) without symptomatic obstruction, we suggest anticoagulation (IV UFH bridging to optimized VKA) plus aspirin (75 to 100 mg/day), with close follow-up with echocardiography to assess for thrombus resolution or progression. Diagnosis of thrombus is confirmed if the mass resolves with optimized antithrombotic therapy.

Target international normalized ratio (INR) levels following resolution of valve thrombosis are discussed below. (See 'Optimized antithrombotic therapy' below and 'Antithrombotic therapy after resolution of valve thrombosis' below.)

Management of patients with left-sided mobile thrombus of ≥0.3 cm in diameter or a large nonmobile thrombus (≥0.8 cm²) is discussed above. (See 'Recommendations for urgent therapy' above.)

COMPONENTS OF THERAPY — Management of PVT involves management of the acute risk and selection of therapy for long-term management. Management options include medical therapy (anticoagulation and fibrinolysis) and surgical therapy (valve replacement). Factors influencing the choice of therapy include impact of any valve obstruction on functional status (New York Heart Association [NYHA] class (table 1)), valve location (left- or right-sided), thrombus size, thrombus mobility, and associated functional status [1,2,7,8]. While thrombus size is commonly used as a factor guiding management, it should be noted that it is difficult to quantify thrombus size due to prosthesis imaging artifact and other technical limitations.

The following approach is based largely on expert opinion. Randomized controlled data for the therapy of PVT are not available, and each therapeutic option has important limitations, including perioperative risk of mortality with valve surgery, risk of bleeding and systemic embolization with fibrinolytic therapy, and risk of failure to improve with intravenous (IV) heparin therapy.

The following are in broad agreement with those in the 2020 American College of Cardiology/American Heart Association valvular heart disease guidelines [2]. A somewhat similar approach was recommended in the 2021 European Society of Cardiology guidelines [1].

Medical therapy for heart failure — Among patients with symptomatic prosthetic valve obstruction, medical therapy for heart failure (HF) is limited to use as a temporizing measure for patients awaiting treatment of the cause of obstruction and as palliation (eg, for patients with obstructive pannus who are not candidates for valve surgery). Medical treatment of symptomatic HF may include cautious use of diuretics and other medical therapy (eg angiotensin converting enzyme inhibitor), given risk of destabilization with attempted therapy. (See "Treatment of acute decompensated heart failure: General considerations" and "Treatment of acute decompensated heart failure: Specific therapies".)

Limited data are available on the efficacy of medical management of HF in this setting, but the expected prognosis is poor given the known natural history of medically treated HF in patients with native valve stenosis (eg, aortic stenosis and mitral stenosis).

Optimized antithrombotic therapy — For patients with nonobstructive prosthetic valve thrombus <0.8 cm², we suggest optimized anticoagulation (with IV unfractionated heparin [UFH] followed by vitamin K antagonist [VKA]) plus aspirin 75 to 100 mg/day with echocardiographic follow-up based upon limited evidence from observational studies [9-11]. These observational studies reported at least partial resolution of thrombus with anticoagulation (with or without aspirin) in one week in 72 to 100 percent of patients with nonobstructive PVT. Small studies have suggested that the risk of a major complication (stroke or development of obstruction) is lower in patients with smaller (<5 mm) versus larger thrombi associated with a mechanical mitral valve [9,12,13].

Fibrinolytic therapy

Protocols — For patients with PVT with an indication for fibrinolysis (also known as thrombolysis), we suggest the following ultraslow infusion low-dose protocol based upon observational studies described below [14] (see 'Evidence' below). Follow-up imaging is performed to evaluate the efficacy of fibrinolytic therapy with transthoracic echocardiography (TTE) generally used to identify effect on the gradient across the prosthetic valve in cases of obstruction and transesophageal echocardiography (TEE) generally used to identify thrombus size and prosthesis appearance.

●Assess for contraindications to fibrinolytic therapy (which are the same as those in the setting of myocardial infarction). (See "Acute ST-elevation myocardial infarction: The use of fibrinolytic therapy", section on 'Contraindications'.)

●If fibrinolysis is contraindicated, refer for valve surgery (thrombectomy or repeat valve replacement).

●If no contraindications to fibrinolysis, hold anticoagulants during fibrinolytic therapy and wait until international normalized ratio (INR) is <2.5 (or activated partial thromboplastin time [aPTT] <50 seconds if patient was receiving UFH) prior to starting fibrinolytic therapy.

●Administer IV 25 mg alteplase infused over 25 hours with no bolus. This is followed by a six-hour infusion of UFH (70 unit/kg bolus and 16 unit/kg/hour [up to 1000 units/hour] with a target aPTT of 1.5 to 2.0 times the control value).

●For patients with prosthetic valve obstruction, perform TTE to assess prosthetic valve gradient.

•If gradient is reduced, perform TEE:

-If TEE shows partial resolution of thrombus (<75 percent reduction in size), repeat 25 mg alteplase infusion over 25 hours followed by a six-hour infusion of UFH, and then repeat TEE.

-If TEE shows resolution of thrombus (≥75 percent reduction in size), stop alteplase and start UFH and VKA. (See 'Antithrombotic therapy after resolution of valve thrombosis' below.)

•If gradient is not improved, repeat 25 mg alteplase infusion over 25 hours followed by six-hour infusion of UFH, and then repeat TTE.

●For patients with nonobstructive thrombosis, repeat TEE.

•If thrombus is resolved (≥75 percent reduction in size), stop alteplase and start UFH and VKA. (See 'Antithrombotic therapy after resolution of valve thrombosis' below.)

•If thrombus is unchanged or only partially resolved (<75 percent reduction in size), repeat 25 mg alteplase infusion over 25 hours followed by UFH six-hour infusion, then repeat TEE.

●For patients with persistent thrombus on repeat TEE, the alteplase 25 mg infusion over 25 hours (followed by UFH six-hour infusion) can be repeated as needed (with TEE evaluation after each dose) up to a maximum cumulative dose of 200 mg of alteplase. Most patients are expected to require three or fewer infusions [14,15].

When successful thrombolysis has been confirmed, UFH and VKA therapy is initiated [1,2]. UFH is continued until VKA achieves the target INR for two consecutive days [2]. VKA therapy (including target INR) and aspirin therapy after PVT is discussed below. Management of antithrombotic therapy after treatment of valve thrombosis is discussed below. (See 'Antithrombotic therapy after resolution of valve thrombosis' below.)

Evidence — Limited evidence is available to guide fibrinolytic agent use in patients with PVT. Only observational data are available on the efficacy and safety of fibrinolytic treatment regimens for PVT. Data on head-to-head comparison of various thrombolytic regimens are lacking, with most studies confined to single-center experience. Most published evidence on fibrinolysis for PVT is related to alteplase, with only case reports available on tenecteplase and reteplase. Streptokinase was the first agent successfully used for PVT, but this agent is no longer available in the United States.

For left-sided PVT — Most studies of fibrinolytic therapy for PVT have focused mainly on left-sided PVT. Studies using an echocardiogram-guided slow or ultraslow infusion, low-dose fibrinolytic protocol have demonstrated high rates of efficacy (85 to 90 percent or higher [14,16,17]) with relatively low rates of complications (eg, 10.5 percent including no deaths with a six-hour infusion [16]; 6.7 percent [including a 0.8 percent mortality rate] with a 25-hour infusion [14]). Outcomes with these low-dose slow or ultraslow regimens are more favorable than those observed in earlier (pre-2013) fibrinolytic studies with rapid infusion rates and higher doses (hemodynamic success rate of 75 percent, 30-day mortality rate of 7 percent, thromboembolism rate of 13 percent, and major bleeding rate of 6 percent) [2].

Complications following fibrinolytic therapy include major bleeding, systemic embolism, recurrent PVT, and death [18-20]. Risk factors for complications in patients receiving slow (or ultraslow) infusion fibrinolytic therapy include NYHA class III or IV and large thrombus size (eg, area on TEE ≥1.0 cm² [14,15]). A prior retrospective international registry study of 107 patients with PVT treated with older fibrinolytic therapy protocols found that a thrombus area of ≥1.0 cm² identified patients at higher risk for complications from thrombolysis [21].

The following studies illustrate outcomes with the newer slow or ultraslow infusion low-dose fibrinolytic protocols:

●A single-center historical comparison between five fibrinolytic regimens (rapid streptokinase [1.5 million units over three hours], slow streptokinase [1.5 million units over 24 hours], 100 mg alteplase [10 mg bolus followed by 90 mg over five hours], 50 mg alteplase [six-hour infusion without a bolus], 25 mg alteplase [six-hour infusion without a bolus]) concluded that efficacy of the fibrinolytic agents was similar (69 to 85 percent), but complications were lowest with the 25 mg alteplase six-hour infusion regimen (10.5 percent) [16].

●In a study of 120 episodes of PVT in 114 patients with median age 49 years, an ultraslow regimen consisting of alteplase 25 mg infusion over 25 hours with no bolus (which was repeated based on TTE/TEE findings up to eight times up to a total of 200 mg) was successful in 90 percent of patients, with a 6.7 percent complication rate (0.8 percent death, 3.3 percent nonfatal major complications, and 2.5 percent minor) [14]. The median number of fibrinolysis infusions was 2 (range 1 to 8). NYHA class III/IV was the only independent predictor of fibrinolytic treatment failure. Predictors of complications were presence of atrial fibrillation, larger thrombus area (>1 cm²), and higher NYHA class; the prevalence of complications was highest in patients with class IV symptoms (75 percent). Death occurred in one patient with NYHA class IV symptoms.

●In a study of 27 patients aged ≥65 years with PVT treated with a variety of repeated cycles of fibrinolytic therapy (predominantly 25 mg of alteplase over 6 or 25 hours), the cumulative success rate was 85.2 percent [15]. There was one death, one rethrombosis, two who did not respond to fibrinolytic therapy, and two minor complications (one transient ischemic attack and one access site hematoma). Adverse events were more frequent in patients with higher NYHA functional class (rates of 0, 15.4, 25, and 100 percent with NYHA class I, II, III, and IV). Thrombus area ≥1.1 cm² was the only independent predictor of adverse events.

For right-sided PVT — The limited data available on the management of patients with right-sided PVT suggest that fibrinolytic therapy is effective in most cases [8,22]. We suggest using the fibrinolytic protocol described above for patients with either left-sided or right-sided PVT, although most patients treated with this regimen have had left-sided PVT. (See 'Protocols' above.)

A series of 16 patients with obstructive PVT of tricuspid (eight) or pulmonic (eight) mechanical valves were treated with fibrinolysis (alteplase or streptokinase) [22]. All except one patient had an INR <2 at the time of presentation and median time from valve implantation was 18 months (range 8 to 36 months). All patients with pulmonic PVT had complete resolution of obstruction in response to fibrinolytic therapy and there were no in-hospital deaths. Six of eight patients with tricuspid PVT had complete resolution of obstruction in response to fibrinolytic therapy. One patient with tricuspid PVT treated with streptokinase had a partial response, eventually underwent repeat tricuspid valve replacement, and died three months later. One patient with tricuspid PVT treated with streptokinase failed to respond, was not deemed a surgical candidate, and died in hospital.

Surgery — Limited observational data are available on the role of surgery in patients with prosthetic valve obstruction or thrombosis. Surgery for prosthetic valve obstruction or thrombosis (valve replacement or thrombectomy) is associated with high operative mortality (overall 30-day mortality of 10 to 15 percent [2]) that is largely related to clinical functional class (eg, 17.5 percent in patients with NYHA class IV symptoms (table 1) compared with 4.7 percent with NYHA class I to III symptoms in a review of 106 patients [23]). Mortality rates as high as 35 percent have been described in critically ill patients [24].

Comparison of surgery with fibrinolysis — Limited evidence is available to compare outcomes with surgery and fibrinolysis in patients with PVT.

Two systematic reviews with meta-analyses included different studies and reached differing conclusions. The later review included one study with a group treated with slow infusion low-dose fibrinolytic therapy [16], but neither systematic review included data on the ultraslow infusion protocol described above [14]. Thus, neither systematic review provides an adequate comparison of current treatment options.

●A meta-analysis included seven observational studies comparing surgery and fibrinolytic therapy for PVT [19]. Among a total of 690 episodes of PVT in 598 patients, 244 were treated with fibrinolysis, and 446 were treated with urgent surgery. The majority of patients presented with severe functional impairment (NYHA class III or IV). Mortality rates were similar with surgery and fibrinolysis (13.5 versus 9 percent). Complete restoration of valve function was nominally but not significantly higher with surgery (86.5 versus 69.7 percent; p = 0.07). Surgery was associated with significantly lower rates of thromboembolism (1.6 versus 16 percent), major bleeding (1.4 versus 5 percent), and recurrent PVT (7.1 versus 25.4 percent).

●A later meta-analysis included 48 studies of surgery and/or fibrinolytic therapy for PVT with a total of 2302 patients [25]. The mortality rate for patients treated with surgery was significantly higher than for patients treated with fibrinolytic therapy (18.1 versus 6.6 percent). Success of therapy (defined as survival not requiring surgery after therapy) was similar in the two groups (81.9 versus 80.7 percent). Surgery was associated with significantly lower rates of thromboembolism (4.6 versus 12.8 percent), but rates of stroke (4.3 versus 5.6 percent) and bleeding (4.6 versus 6.8 percent) were similar.

Though controlled data are lacking, major society guidelines have suggested individualized assessment of clinical factors that may favor one treatment option over another (eg, surgery for larger thrombi and fibrinolysis for small thrombi) [1,2]. (See 'Individualized assessment of treatment options' above.)

ANTITHROMBOTIC THERAPY AFTER RESOLUTION OF VALVE THROMBOSIS — Patients with PVT treated with antithrombotic therapy and/or fibrinolytic therapy are at risk for recurrent PVT (eg, 6 percent during a median of 10 months follow-up after ultraslow fibrinolytic therapy). Thus, these patients require careful follow-up including an optimized antithrombotic regimen.

When PVT occurs despite antithrombotic therapy, a key initial step is to determine which antithrombotic agents (eg, warfarin and/or aspirin) the patient was taking and the adequacy of anticoagulation (including recent duration in the therapeutic range). The risk of bleeding complications with increased intensity of anticoagulation should also be assessed. Standard antithrombotic therapy for a mechanical valve includes low-dose aspirin (75 to 100 mg/day) plus an anticoagulant (vitamin K antagonist [VKA] or heparin). Direct oral anticoagulants (oral direct thrombin inhibitors and factor Xa inhibitors) are not recommended for use in patients with mechanical prosthetic valves. (See "Antithrombotic therapy for mechanical heart valves", section on 'Long-term anticoagulation'.)

If antithrombotic therapy was inadequate prior to valve thrombosis or thromboembolism, institution of adequate therapy, including optimization of international normalized ratio (INR) range (eg, with patient education, more frequent monitoring, management by a dedicated pharmacist-led anticoagulation clinic, or patient self-monitoring), should be the first therapeutic step [1,2].

The following approach is suggested for patients with mechanical valves who have been treated for valve thrombosis, although data regarding efficacy of these regimens are lacking:

●For patients with thromboembolism who were adequately anticoagulated with VKA (eg, warfarin) but not receiving aspirin, add aspirin (75 to 100 mg/day).

●For patients with thromboembolism or valve thrombosis while anticoagulated to a goal INR of 2.5 (eg, patients with mechanical aortic valve replacement without additional risk factors) and taking aspirin, increase the goal INR to 3.0 [2].

●For patients with thromboembolism or valve thrombosis when anticoagulated to a goal INR of 3.0 plus aspirin, the goal INR may need to be increased to 4.0 [2].

This approach to adjustment of antithrombotic therapy is generally consistent with the 2020 American College of Cardiology/American Heart Association valvular heart disease guidelines [2].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Cardiac valve disease" and "Society guideline links: Anticoagulation in pregnancy".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Prosthetic valves (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Evaluation – The evaluation of mechanical prosthetic valve obstruction focuses on distinguishing between thrombus and pannus since thrombus may be treated by anticoagulation, thrombolysis, or valve surgery (thrombectomy or repeat valve replacement) while pannus can be treated only by valve surgery. Infection should also be considered and excluded. (See 'For valve obstruction' above and "Mechanical prosthetic valve thrombosis or obstruction: Clinical manifestations and diagnosis", section on 'Differentiate between thrombus and pannus as main cause of obstruction' and 'Management based upon diagnosis' above.)

●Moderately to severely symptomatic left sided valve obstruction – Patients with a thrombosed left-sided mechanical prosthetic heart valve with moderate to severe (New York Heart Association [NYHA] functional class III or IV) symptoms of valve obstruction require immediate referral to a heart-valve team for consideration of either slow-infusion, low-dose fibrinolytic therapy or emergency surgery.

Factors determining choice of surgery or fibrinolytics include available local surgical expertise, clinical features (surgical risk, functional class, contraindication to fibrinolysis, first versus recurrent episode of valve thrombosis), concurrent need for other surgical intervention, and thrombus size.

Patients with a thrombosed left-sided mechanical valve with severe symptoms (NYHA class IV) require urgent intervention. For most of these patients, we suggest surgery rather than fibrinolysis (Grade 2C). The urgency of surgery is based upon the acuity and severity of patient symptoms. Prior to surgery, the patient is treated with intravenous (IV) unfractionated heparin (UFH) with goal activated partial thromboplastin time (aPTT) 2 to 2.5 times control. (See 'Recommendations for urgent therapy' above.)

●Large or mobile thrombus – Patients with left-sided mechanical valve thrombosis (obstructive or nonobstructive) with a mobile thrombus ≥0.3 cm in diameter or a large nonmobile thrombus (≥0.8 cm²) require urgent intervention. For most of these patients, we suggest surgery rather than fibrinolysis (Grade 2C). (See 'Recommendations for urgent therapy' above.)

●Mildly to moderately symptomatic left sided valve obstruction – For patients with obstructive, left-sided mechanical prosthetic valve thrombosis (PVT) with NYHA class I to III symptoms and a small thrombus (<0.8 cm²), we suggest a trial of therapeutic anticoagulation with IV UFH for several (eg, five to seven) days with goal aPTT 2 to 2.5 times control (Grade 2C). Aspirin 75 to 100 mg daily is continued during this therapy. Diagnosis of thrombus is confirmed if the mass resolves with optimized antithrombotic therapy. (See 'Optimized antithrombotic therapy' above.)

If obstructive thrombus persists after a trial of UFH, we suggest fibrinolytic therapy (Grade 2C). (See 'Fibrinolytic therapy' above and 'For left-sided PVT' above.)

●Obstructive right-sided valve thrombosis – For patients with obstructive right-sided mechanical PVT, we suggest fibrinolytic therapy (Grade 2C). Aspirin 75 to 100 mg daily is continued, and vitamin K antagonist (VKA) is held during this therapy. (See 'Fibrinolytic therapy' above and 'For right-sided PVT' above.)

●Symptomatic patients refractory to fibrinolysis – For patients with left- or right-sided obstructive mechanical PVT with persistent NYHA class II (or greater) symptoms despite optimal anticoagulation and fibrinolysis or with absolute contraindications to fibrinolytic therapy, we suggest valve surgery (Grade 2C). (See 'Surgery' above.)

●Obstructive pannus – For operable patients with symptomatic severe mechanical prosthetic heart valve obstruction with presumptive diagnosis of pannus, we suggest valve surgery (Grade 2C). (See 'Surgery' above.)

For patients with obstruction with imaging findings indeterminate for thrombus or pannus, management is generally as for pannus unless clinical features are strongly suggestive of thrombus as the predominant cause of obstruction.

●Nonobstructive small thrombus – For patients with nonobstructive, left- or right-sided mechanical PVT with a small thrombus (<0.8 cm²), we suggest anticoagulation (IV UFH bridging to optimized VKA) plus aspirin (75 to 100 mg daily) (Grade 2C). Aspirin 75 to 100 mg daily is continued during this therapy. (See 'For valve thrombosis without obstruction' above and 'Optimized antithrombotic therapy' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff would like to thank Catherine M Otto, MD, who contributed to earlier versions of this topic review.