Imaging methods for prostheses
The primary first-line examination (first-line examination) is echocardiography. Immediately after implantation, a baseline study (2D and Doppler) is mandatory to establish a reference point for comparison when dysfunction is suspected in the future.
Additional methods are used to clarify the picture:
- Radiography: frontal views can determine the valve type by its orientation vector. A mitral prosthesis produces a left atrioventricular vector, while an aortic prosthesis produces a left ventriculoaortic vector.
- Computed tomography (CT): highly informative for mechanical valves. It allows visualization of anatomy in vivo and evaluation of the leaflets. CT is also indispensable for planning transcatheter aortic valve implantation (TAVI) procedures, where the aortic root and peripheral arteries are assessed.
- MRI (Cine-MRI): its utility is reduced due to metallic components. A characteristic magnetic susceptibility artifact (susceptibility artefact) occurs — a massive "black spot" that obscures the valve itself. However, the method is excellent for assessing pseudoaneurysms.
Complications: wear and infections
Biological valves, such as porcine bioprostheses, have low durability. Degeneration, fibrosis, calcification, and leaflet tears begin to manifest approximately from the 5th year after surgery.
Infective endocarditis is a rare (0.9–4.4%) but formidable complication. Causative agents are typically coagulase-negative staphylococci, Serratia marcescens, Staphylococcus aureus, or Candida albicans.
Features of the infectious process:
- The ostia of the coronary arteries and the fibrous annulus are affected.
- High-velocity regurgitant jets destroy tissues, causing local abscesses and paravalvular regurgitation.
- Vegetations and pannus (pannus) develop, which can physically block the moving parts of the prosthesis.
Thromboembolism and regurgitation
Prosthesis thrombosis is an emergency surgical situation. It can occur spontaneously even against the background of adequate anticoagulant therapy. Thrombosis of a mitral prosthesis is more common than an aortic one. While in older models the embolic risk reached up to 37%, the introduction of tissue-covered prostheses has reduced it to 3–5%.
Valve dysfunction may manifest as valvular regurgitation:
- Mild regurgitation is considered a variant of normal for mechanical models.
- Significant regurgitation indicates ring dehiscence (ring dehiscence), thrombosis, or leaflet impingement. In case of sudden pulmonary edema and increased heart size, acute failure should be immediately suspected and an echocardiogram performed.
Briefly: answers to topical questions
What are the structural types of mechanical heart valve prostheses?
- Caged-ball (central ball occluder valve) — a spherical occluding element.
- Caged-disc (central caged disc occluder valve) — a disc occluding element in a special cage structure.
- Eccentric monocuspid disc (eccentric monocuspid disc valve) — a valve with a single eccentric disc leaflet.
- Bileaflet (bileaflet disc valve) — a mechanical prosthesis with two leaflets.
To remember the limitations of MRI: a mechanical valve produces a massive magnetic susceptibility artifact, which appears on images as a "black hole" that erases the signal from the valve itself and adjacent tissues.
Class and exam questions
Why do patients with a prosthesis undergo a baseline echocardiogram immediately after surgery?
A baseline study is needed to record the ideal initial performance parameters of the valve. New data will be compared against them whenever complications are suspected.
Can mechanical prostheses be evaluated using MRI?
Direct evaluation of mechanical valve leaflets on MRI is impossible due to pronounced metal artifacts. However, the method is effective for detecting paravalvular complications (e.g., pseudoaneurysms).
Why is significant regurgitation on a prosthesis dangerous?
It indicates a serious structural failure: valve ring dehiscence, leaflet jamming by a thrombus, or tissue destruction by infection. Clinically, this can lead to rapid pulmonary edema.
What else to study on this topic
- CT planning for transcatheter aortic valve implantation (TAVI)
- Imaging findings in paravalvular abscesses and fistulas
- Differential diagnosis of primary and secondary cardiac tumors
- Tissue characterization of cardiac masses on MRI
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