Algorithm for evaluation of mechanical prosthetic heart valve obstruction (thrombus versus pannus)

TTE: transthoracic echocardiography; TEE: transesophageal echocardiography; CT: computed tomography.
* Evaluation should include assessment of any findings suggestive of prosthetic valve endocarditis. Refer to UpToDate content on the diagnosis and treatment of prosthetic valve endocarditis.
¶ Exclude increased stroke volume as a cause of increased transvalvular gradients.
Δ The urgency of surgery depends upon the acuity and severity of the patient's symptoms.
◊ Since Björk-Shiley and Sorin monoleaflet valves are not well visualized by CT due to severe artifact, fluoroscopy or TEE is preferred for visualization of leaflet motion for these valve types.
§ Some experts prefer CT to TEE as the primary test to evaluate prosthetic leaflet motion and appearance (except for monoleaflet valves).
¥ Echodensity of a mass can be evaluated using the intensity ratio (defined as the intensity of mass/intensity of prosthesis). Intensity ratio ≤0.45 is low; intensity ratio >0.45 is high.
‡ CT imaging is not generally helpful for a monoleaflet mechanical valve; for such valves, fluoroscopy enables assessment of leaflet motion if TEE is indeterminate.
† CT characteristics of mass consistent with thrombus include low attenuation, irregular shape, and attachment to leaflets or hinge points.
** CT characteristics of mass consistent with pannus include high attenuation (HU ≥145) and extension along the valve ring.
¶¶ When imaging is indeterminate for thrombus or pannus, management is generally as for pannus unless clinical features are strongly suggestive of thrombus.