What is the recommended thrombolytic regimen, dosing, and monitoring for an acutely obstructed (choked) prosthetic aortic valve in a patient who is a poor surgical candidate or when emergent surgery is unavailable?

Thrombolysis for Obstructed Prosthetic Aortic Valve

For an acutely obstructed prosthetic aortic valve in a poor surgical candidate or when surgery is unavailable, administer recombinant tissue plasminogen activator (rtPA) 10 mg IV bolus followed by 90 mg infused over 90 minutes with concurrent unfractionated heparin, or alternatively streptokinase 1,500,000 units over 60 minutes without heparin. 1

Clinical Context and Decision Framework

The management of prosthetic valve thrombosis is inherently high-risk regardless of treatment choice—surgery carries operative mortality from emergency reintervention, while thrombolysis risks bleeding, systemic embolism, and recurrent thrombosis. 1 However, fibrinolysis should be considered when surgery is not available, the patient is at very high surgical risk, or for right-sided prostheses (Class IIa recommendation). 1

When to Choose Thrombolysis Over Surgery

Thrombolysis is the preferred approach in these specific scenarios:

• Critically ill patients unlikely to survive surgery due to severe comorbidities or profoundly impaired cardiac function that existed before valve thrombosis developed 1
• Surgery not immediately available and the patient cannot be safely transferred 1
• NYHA Class I-II symptoms with small thrombus burden and recent symptom onset 2
• Right-sided valve thrombosis (tricuspid or pulmonary positions) where success rates are higher and systemic embolic risk is lower 1

Thrombolytic Regimens and Dosing

Primary Regimen (Preferred for Hemodynamic Instability)

Recombinant tissue plasminogen activator (rtPA):

• 10 mg IV bolus followed by 90 mg infused over 90 minutes
• Administer with concurrent unfractionated heparin (UFH) 1
• This short protocol is recommended for hemodynamically unstable patients 1

Alternative Regimen

Streptokinase:

• 1,500,000 units infused over 60 minutes
• Administered without UFH 1
• Loading dose of 500,000 IU over 20 minutes followed by 1,500,000 IU over 10 hours is an alternative protocol 1

Modified Protocols for Stable Patients

• Lower-dose rtPA: 20 mg IV bolus followed by 10 mg/hour for 3 hours may be appropriate in some situations 1
• Slow-infusion protocol: rtPA 25 mg over 25 hours with repeat dosing if needed, showing hemodynamic success rates >90% with embolic event rates <2% 2
• Longer infusion durations can be used in hemodynamically stable patients 1

Monitoring During Thrombolysis

Immediate Assessment

• Confirm diagnosis with transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) before initiating therapy 1, 3
• Cinefluoroscopy or CT scan if promptly available to assess leaflet motion 1
• Administer 5000 units of heparin IV immediately upon suspicion of valve thrombosis 1

During Infusion

• Hold heparin and glycoprotein IIb/IIIa inhibitors during rtPA infusion, but aspirin can be continued 1
• Serial echocardiography to document restoration of normal valve function 4
• Continuous hemodynamic monitoring for signs of bleeding or embolism 1

Post-Thrombolysis Management

• Resume IV UFH after successful fibrinolysis until vitamin K antagonist (VKA) achieves therapeutic INR 1
• Target INR 3.0-4.0 for aortic prosthetic valves 1
• Target INR 3.5-4.5 for mitral prosthetic valves 1
• Add low-dose aspirin (100 mg daily) to warfarin for all mechanical valves to prevent recurrence 2

Critical Success and Failure Predictors

Factors Favoring Success

• Recent onset of symptoms (mean 81 ± 65 hours in successful cases) 4
• Transesophageal echocardiographic evidence of fresh clot rather than chronic pannus 4
• Preserved disc excursions on imaging 4
• Aortic position (85% success rate versus 63% for mitral) 5

Factors Predicting Failure

• Mitral prostheses have lower success rates than aortic 1
• Chronic thrombosis or presence of pannus (difficult to distinguish from thrombus) 1
• Large thrombus burden (>10 mm or >0.8 cm²) 3, 2
• Mobile or large clots extending beyond the prosthesis 1

Complications and Risk Mitigation

Major Risks

• Systemic embolism: 14.6% incidence, including 4 major cerebral emboli with death in one series 5
• Bleeding complications: Major hemorrhage in 2-5% of cases 6, 5
• Recurrent thrombosis: 25.4% with fibrinolysis versus 7.1% with surgery 1
• Mortality: Overall 4-9 deaths reported across series 6, 5

Common Pitfalls to Avoid

• Do not delay diagnosis by attributing symptoms to primary heart failure rather than valve thrombosis 3
• Do not use urokinase—it is less effective than rtPA or streptokinase 1
• Do not use direct oral anticoagulants (DOACs) in mechanical valve patients—they are contraindicated 2
• Do not assume all dyspnea is thrombosis—confirm with imaging before treatment 3

When to Proceed Directly to Surgery

Emergency valve replacement remains the Class I recommendation for:

• Critically ill patients with NYHA Class III-IV symptoms without serious comorbidity 1
• Large mobile thrombus (>0.8 cm²) with high embolic risk 1, 3
• Recurrent valve thrombosis after previous thrombolysis 2
• Contraindications to fibrinolysis 2
• Suspected pannus ingrowth rather than acute thrombus 2

The overall success rate for surgical intervention approaches 90% in patients without contraindications, with lower rates of thromboembolism (1.6% versus 16%), major bleeding (1.4% versus 5%), and recurrent thrombosis (7.1% versus 25.4%) compared to fibrinolysis. 1 However, thrombolysis does not preclude subsequent surgery if unsuccessful, and patients proceed to operation in better hemodynamic condition with lower risk. 6