12.3 Prosthetic Obstruction, Regurgitation, Thrombosis, and Patient–Prosthesis Mismatch

Treat a high gradient as the start of the investigation

Retrieve valve type, size, position, implant date, procedure details, stable postoperative baseline, symptoms, anticoagulation history, fever or embolic events, BP, heart rate, rhythm, and body surface area. Repeat imaging if Doppler alignment, tracing, or PW location is questionable. A high gradient may reflect true obstruction, but also anemia, fever, pregnancy, sepsis, significant regurgitation, shunt, tachycardia, prosthesis–patient mismatch (PPM), supra- or subvalvular obstruction, pressure recovery, or the high-velocity central orifice of a bileaflet valve. Low flow can hide important obstruction.

Map velocity with PW proximal to the valve before CW interrogation, and acquire CW from every appropriate window. Compare velocity, mean gradient, contour, VTI, DVI, EOA, acceleration time for aortic valves, PHT for atrioventricular valves, and chamber response with baseline and device-specific references. A new rounded, late-peaking aortic envelope, prolonged acceleration, falling DVI or EOA, and rising gradient is more concerning than one isolated high value. Current ASE guidance requires at least one flow-dependent measure such as velocity or mean gradient and one less flow-dependent measure such as DVI or EOA to support significant prosthetic aortic stenosis.

For surgical aortic prostheses, a rounded symmetric jet, acceleration time above 100 ms, acceleration-time/ejection-time ratio above 0.37, DVI below 0.25, EOA markedly below the type-size reference, and mean gradient at least 35 mmHg form a significant-obstruction pattern when flow and technique are appropriate. These are integrated markers, not independent verdicts. For a prosthetic mitral valve, a mean gradient above 10 mmHg at a normal heart rate, PHT above 200 ms, DVI above 2.5, and EOA below 1.0 cm² support significant stenosis, but tachycardia and important MR must be excluded and motion demonstrated. Right-sided prostheses require respiratory averaging, correct flow assumptions, and position-specific references.

Determine the pathologic category

Structural valve dysfunction is permanent intrinsic deterioration: bioprosthetic leaflet thickening, fibrosis, calcification, tear, stent deformation, or mechanical component failure. Nonstructural dysfunction includes PPM, paravalvular leak, malposition, entrapment, chamber or root dilation, and pannus. Thrombosis and endocarditis are separate categories that may cause obstruction, regurgitation, or both. Categories can coexist.

Thrombosis may present with new symptoms, embolism, altered mechanical sounds, a rising gradient, leaflet thickening, or reduced leaflet/occluder motion, especially with inadequate anticoagulation. TTE establishes hemodynamic change but often cannot distinguish thrombus from pannus by echogenicity. TEE can show atrial-side mitral thrombus and en-face motion; cine fluoroscopy measures mechanical opening and closing angles; gated CT depicts mechanical motion, pannus, thrombus, and hypoattenuated leaflet thickening in bioprostheses. Do not delay urgent communication for a stuck mechanical occluder or hemodynamic instability while pursuing perfect images.

Degeneration often evolves over years with progressive tissue thickening, calcification, restriction, or tear. Pannus is fibrous periannular ingrowth and tends to be fixed; thrombus can occur rapidly, but timing alone is not definitive. Vegetation, abscess, new paravalvular leak, or rocking suggests infection or dehiscence and requires prompt escalation. Compare with postoperative material so pledgets, sutures, and expected shadow are not mislabeled.

Localize regurgitation and distinguish PPM

First decide whether flow is expected physiologic leakage, abnormal intravalvular regurgitation through the prosthesis, or paravalvular regurgitation outside the sewing ring or stent. Sweep the whole circumference because shadow can hide jets and multiple leaks cannot be represented by one diameter. Integrate color origin and vena contracta, CW density and contour, flow convergence, downstream venous or arterial reversal, comparative stroke volumes, chamber remodeling, pulmonary pressure, and serial change. A rocking valve plus a new paravalvular jet is dehiscence until urgently evaluated. TEE with 3-D color is often best for mitral or tricuspid leak localization; CMR can quantify regurgitant volume when echo remains discordant.

PPM means the prosthesis is structurally normal and opens normally, but its EOA is too small relative to body size. Calculate indexed EOA = EOA / body surface area and apply position- and BMI-appropriate current thresholds; indexing can overstate aortic PPM in obesity. PPM is usually evident on the stable postoperative baseline and remains relatively stable. Acquired obstruction instead produces new restriction or worsening Doppler values. PPM can coexist with degeneration or thrombosis, and severe PPM can have a normal gradient during low flow, so neither timing nor gradient alone settles the diagnosis.

The final report identifies device and baseline, states acquisition quality, quantifies serial change, separates intra- from paravalvular regurgitation, describes motion and masses, lists competing causes of a high gradient, and names unresolved limitations. Recommend interpreter-directed TEE, CT, fluoroscopy, CMR, stress echo, or catheter hemodynamics when the clinical and TTE data remain discordant.

Before labeling interval obstruction, remeasure the LVOT at the original site and match heart rate, stroke volume, Doppler window, and beat selection; an altered PW sample alone can change DVI and calculated EOA.