You may wish to check out three more related articles on my blog:
Protocol for thrombolysis of prosthetic valve thrombosis [ Ссылка ]
Low dose t-PA for prosthetic valve thrombosis in pregnancy: [ Ссылка ]
Multi detector CT for differentiation of prosthetic valve thrombus from pannus: [ Ссылка ]
Discussion on prosthetic valve thrombosis. Obstruction of a prosthetic valve by a non-infective thrombus is what we mean by prosthetic valve thrombosis. Size of the thrombus is important in deciding the management.
1. Endothelial factors: Suture zone endothelialization occurs in 3-4 weeks. Risk of thrombosis is higher prior to endothelialization if anticoagulation is suboptimal.
2. Hemodynamic factors: Localised region of turbulent flow causes endothelial trauma, and damage to blood cells, releasing adenosine diphosphate which promote platelet aggregation. 3. Coagulation factors
Insufficient anticoagulation, mitral/tricuspid position, hypercoagulable state, presence of associated atrial thrombus. Pannus can occur along with the thrombus as well.
Bioprosthetic heart valves are at risk of thrombosis in the initial period after implantation till they get endothelialized. Mechanical prosthetic heart valves have a lifelong risk of prosthetic valve thrombosis and thromboembolism and hence need lifelong anti coagulation.
Tricuspid prosthetic valve is more prone for thrombosis due to the low velocity of blood flow. Mitral valve has a higher risk than aortic valve because of the lower blood flow velocity across it.
Clinical presentations: 1. Clinically silent prosthetic valve thrombosis. 2. Prosthetic valve thrombosis with embolic episodes like cerebral, coronary, or peripheral embolism can occur in up to 25% cases. 3. Hemodynamic problem with evidence of valve thrombosis.
Prosthetic valve thrombosis can present with fever in the setting of infective endocarditis. Fever can occur in prosthetic valve thrombosis even without endocarditis.
Diagnosis of prosthetic valve thrombosis: High resolution sound spectrograph can detect valve thrombosis by the change in the valve sounds. This is probably similar to suspicion of thrombosis when audible valve sound intensity decreases clinically. Patients are routinely instructed to listen for the valve sounds in a quiet room and report back if there is a decrease in intensity.
Cine fluoroscopy is useful as it can detect decreased leaflet and poppet movements as well as abnormal movement of the valve cage. Short video clipping follows describing bileaflet prosthetic mitral valve on fluoroscopy.
Video
Echocardiography is an important tool for evaluation of prosthetic valve thrombosis. Thrombus can be visualised by echocardiography, better with transesophageal than transthoracic echocardiography.
Gradients and valve areas can be estimated. Dimensionless obstruction indices are the ratio of subvalvular/valvular velocities and velocity time integrals.
Management of prosthetic valve thrombosis: If the thrombus in the prosthetic valve is less than 5 mm in size, only intravenous heparin is recommended. For larger thrombi there are two options: thrombolysis versus surgical treatment.
Thrombolysis has an initial success rate of 70 -80%, but there is a 5 -22% risk of embolism, and 5 -12% risk of disabling stroke. Thrombolysis is the preferred treatment for right sided prosthetic valve thrombosis and small left sided thrombi.
Surgical treatment has a combined risk of death or stroke of 9%. In patients presenting with stroke, surgery is the first option as thrombolysis is contraindicated.
