12.2 Normal Mechanical and Bioprosthetic Valve Assessment

Identify the prosthesis before judging it

CCI task C13 includes assessment of prosthetic valves. Start by retrieving the operative note, device card, and prior studies. Record valve position; manufacturer and model when known; mechanical, surgical bioprosthetic, homograft, or transcatheter design; labeled size; implant date; and whether it is valve-in-valve, valve-in-ring, root replacement, or a valved conduit. Document symptoms, blood pressure, heart rate, rhythm, height, weight, body surface area, and relevant anticoagulation information. For atrioventricular prostheses, heart rate materially affects diastolic filling and mean gradient.

The baseline TTE should have been obtained after implantation under stable hemodynamic conditions. It records the patient's normal leaflet or occluder motion, velocity, mean gradient, DVI, effective orifice area (EOA), regurgitation, and chamber response. Compare today's data with that baseline and with reference values for the same type and size. A generic cutoff cannot account for design: a small mechanical valve normally has different hemodynamics from a larger stented tissue or transcatheter valve. Never use labeled size as the measured LVOT diameter.

Mechanical designs include contemporary bileaflet valves and less common single tilting-disk or older caged-ball valves. They are durable but generate strong reverberation and shadow. Bileaflet valves divide forward flow into one small central and two larger lateral orifices; CW may capture the high-velocity central jet and overestimate gradient, especially in a small valve or high-flow state. Bioprostheses use tissue leaflets mounted on a stent, implanted without a stent, placed as a homograft, or deployed by catheter. Tissue cusps are more directly visualized but can still be obscured by the frame or calcification.

Image structure, motion, stability, and expected leakage

Use standard and off-axis views that place the prosthesis in long and short axis. Sweep through the entire sewing ring or stent rather than relying on one plane. Describe opening and closing of every demonstrated leaflet or occluder, tissue thickness and echogenicity, calcification, unexpected masses, frame shape and position, and surrounding anatomy. A stable ring moves with its annulus; independent excessive rocking plus a paravalvular jet raises concern for dehiscence. Immediately postoperative edema or hematoma and pledgets can resemble pathologic tissue, making the early baseline essential.

Mechanical valves require small intentional washing jets to reduce stasis. These are usually narrow, predictable, symmetric intravalvular jets defined by the design. Do not call them pathologic simply because color is present. Conversely, do not dismiss a new, broad, eccentric, or paravalvular jet as washing flow. A normal tissue valve may have trivial central closure regurgitation, but a visible gap, leaflet tear, or jet outside the sewing ring is not physiologic. Map jet origin in multiple views and distinguish intravalvular from paravalvular flow.

Calculate matched hemodynamics

Record the highest valid forward velocity from all appropriate windows; for an aortic prosthesis, use a nonimaging probe when it improves alignment. Trace the dense modal CW envelope. Peak and mean gradients are flow dependent. Calculate continuity EOA as:

EOA = forward stroke volume / prosthetic-valve VTI

The diameter and PW sample must describe the same flow location. In a surgical aortic valve, sample just proximal to the prosthesis without including acceleration. A transcatheter frame can accelerate flow at its inlet and again at the cusps, so follow the recommended matched diameter and PW convention and preserve it for serial studies. LVOT diameter error is squared.

For an aortic prosthesis, DVI = LVOT VTI / prosthetic aortic VTI. It avoids the diameter term but remains wrong if the LVOT sample contains acceleration or is too apical. Record CW contour, acceleration time, and acceleration-time/ejection-time ratio as additional shape and timing evidence. A normal prosthetic aortic signal is usually triangular and early peaking rather than rounded and late peaking.

For a mitral prosthesis, the VTI ratio is inverted: DVI = prosthetic mitral VTI / LVOT VTI. Report the heart rate for the mean gradient. PHT describes pressure decay but is affected by chamber compliance and is not used as a shortcut for continuity EOA. Significant MR can raise mitral velocity and DVI while lowering systemic LVOT flow, so even a normal-looking prosthesis needs a regurgitation screen.

Complete the study with LV and RV size and systolic function, atrial size, wall thickness, other valve disease, estimated pulmonary pressure, venous flow when relevant, and a search for paravalvular complications. Archive representative 2-D, color, PW, and CW data with ECG and settings. A normal report names the valve, size, date, baseline comparison, observed motion and stability, measured hemodynamics, expected physiologic leakage, chamber findings, and limitations. TTE is first line; TEE, CT, fluoroscopy, or CMR is reserved when structure, motion, or flow cannot be resolved adequately.