What is prosthetic valve thrombosis and what are its signs and symptoms?

Prosthetic Valve Thrombosis: Definition and Clinical Presentation

Prosthetic valve thrombosis is a life-threatening complication where blood clots form on or around a prosthetic heart valve (mechanical or bioprosthetic), causing valve obstruction or embolic events, and should be suspected immediately in any patient with a prosthetic valve presenting with recent dyspnea or an embolic event. 1

What Is Prosthetic Valve Thrombosis?

Prosthetic valve thrombosis occurs when thrombus formation interferes with normal valve function, either by:

• Obstructing valve leaflet motion (obstructive thrombosis), leading to increased transvalvular gradients and heart failure symptoms 1
• Creating embolic risk (non-obstructive thrombosis) without significantly impeding valve function 1

The condition occurs predominantly in mechanical prostheses but can also affect bioprosthetic valves. 1 The incidence is approximately 0.5% in aortic and mitral positions, but up to 20% in the tricuspid position. 2 Risk is highest in the mitral position compared to aortic, and within the first 3 months after valve implantation. 3, 4

Cardinal Signs and Symptoms

Acute Presentation

Patients typically present with worsening shortness of breath and signs of heart failure, ranging from mild symptoms to severe acute pulmonary edema. 3 Key presentations include:

• Recent onset dyspnea - the most common presenting symptom 1, 3
• Embolic events - stroke, TIA, retinal occlusion, or systemic thromboembolism 3
• Acute heart failure - orthopnea, paroxysmal nocturnal dyspnea, pulmonary edema 3
• Cardiogenic shock - hypotension and hemodynamic collapse in severe cases 3

Subacute/Insidious Presentation

Valve thrombosis can develop slowly over days to weeks with gradual symptom progression: 3

• Progressive fatigue and exercise intolerance 3
• Gradual worsening of dyspnea on exertion 3
• Increasing NYHA functional class over time 3

Physical Examination Findings

Critical physical examination signs include: 3

• Muffled or absent prosthetic valve closing clicks - suggests impaired leaflet motion 3
• New or changing systolic murmur - indicates altered flow dynamics 3
• Signs of heart failure (elevated JVP, pulmonary rales, peripheral edema) 3

Asymptomatic Presentation

Some patients may be completely asymptomatic, with thrombosis detected only on routine imaging (particularly subclinical leaflet thrombosis). 3 This underscores the importance of surveillance imaging in prosthetic valve patients.

Severity Indicators

High-Risk Features

NYHA Class III-IV symptoms indicate severe valve obstruction and are associated with higher mortality risk. 1, 3 Other concerning features include:

• Acute, sudden worsening - suggests large thrombus burden causing significant obstruction 3
• Hemodynamic instability - cardiogenic shock requiring immediate intervention 3
• Large thrombus size (>10 mm or >0.8 cm²) - associated with higher embolic risk 1

Diagnostic Clues on Imaging

Elevated transvalvular gradients on Doppler echocardiography indicate significant valve obstruction. 3 Additional findings include:

• Reduced or restricted leaflet motion 3
• Visible thrombus on transesophageal echocardiography 1
• Abnormal leaflet motion on fluoroscopy or CT 1

Key Risk Factors

Subtherapeutic anticoagulation is the primary driver of prosthetic valve thrombosis. 5, 4 Specific risk factors include:

• Recent inadequate anticoagulation - subtherapeutic INR levels or interrupted therapy 3
• Increased coagulability states - dehydration, infection, pregnancy 3
• Early postoperative period - first 3 months after implantation 3
• Mitral or tricuspid position - higher risk than aortic position 4, 2
• Older generation mechanical valves - ball and cage valves carry higher risk 4

Diagnostic Confirmation

The diagnosis must be confirmed promptly with transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE). 1 The diagnostic algorithm includes:

• TTE first - assess hemodynamic severity, transvalvular gradients, and valve area 1
• TEE mandatory - visualize thrombus, assess leaflet motion, measure thrombus size 1
• Fluoroscopy or CT - reasonable to assess leaflet motion when echocardiography is inconclusive 1, 4

Critical Differentiating Features

Timing of onset helps differentiate thrombosis from other causes of prosthetic valve dysfunction: 3

• Acute/subacute onset - favors thrombosis over pannus formation 3
• Improvement with intensified anticoagulation - supports thrombosis rather than pannus 3
• Fever and positive blood cultures - suggests endocarditis rather than thrombosis 1

Common Clinical Pitfalls

Symptoms may be mistakenly attributed to primary heart failure exacerbation rather than valve thrombosis, leading to dangerous delays in diagnosis. 3 Other pitfalls include:

• Gradual symptom development may not trigger immediate suspicion 3
• Failure to check INR in all prosthetic valve patients with new symptoms 3
• Inadequate imaging - relying on TTE alone without TEE confirmation 1