Evaluation of Prosthetic Valve Function and TAVI by EchoCG: ASE 2024
What the ASE 2024 Document Changed
The ASE 2024 recommendations completely replaced the 2009 guidelines for evaluating prosthetic valves. The main practical shift is a unified multimodal algorithm for surgical mechanical and biological prostheses, TAVI, valve-in-valve, and valve-in-ring, as well as a clear distinction of causes of high gradients: true obstruction, patient-prosthesis mismatch, high flow, pressure recovery, and measurement errors.
Normal values are not universal for all models. For TAVI, it is especially important to specify the valve type, size, implantation route, and presence of valve-in-valve: ASE 2024 publishes reference EchoCG values for specific devices and sizes, rather than offering a single general gradient for all transcatheter valves.
Minimal EchoCG Protocol
Transthoracic EchoCG remains the first method. The protocol should include: type and size of the prosthesis, implantation date, heart rate and blood pressure during the study, rhythm, Vmax, mean gradient, VTI of the prosthesis, VTI LVOT or RVOT, DVI, calculated effective orifice area, presence and mechanism of regurgitation. For mitral and tricuspid prostheses, heart rate must be recorded, as the gradient sharply depends on diastolic time.
The optimal reference point is an early stable EchoCG after implantation. Any subsequent study is interpreted not only by absolute thresholds but also by changes from the baseline. This is especially critical for TAVI, where normal gradients depend on the design and size of the device.
Aortic Prosthesis and TAVI: Obstruction Thresholds
| Parameter | Normal | Possible Obstruction | Significant Obstruction |
|---|---|---|---|
| Vmax | <3 m/s | 3–4 m/s | >4 m/s |
| Mean Gradient | <20 mm Hg | 20–35 mm Hg | >35 mm Hg |
| DVI | >0.35 | 0.25–0.35 | <0.25 |
| Effective Orifice Area | >1.2 cm² | 0.8–1.2 cm² | <0.8 cm² |
| Acceleration Time, AT | <80 ms | 80–100 ms | >100 ms |
| AT/ET | <0.32 | 0.32–0.37 | >0.37 |
For an aortic surgical prosthesis and TAVI, stenosis cannot be diagnosed by a single high gradient. Consistency is needed: high velocity and gradient, low DVI, reduced EOA, prolonged AT, and a rounded late-peaking Doppler contour. If the gradient is high but DVI is preserved, high flow, anemia, arteriovenous shunt, significant regurgitation, or LVOT measurement error are more often considered.
Mitral Prosthesis: What to Consider Normal
| Parameter | Normal | Possible Obstruction | Significant Obstruction |
|---|---|---|---|
| Peak Velocity | <1.9 m/s | 1.9–2.5 m/s | >2.5 m/s |
| Mean Gradient | ≤5 mm Hg | 6–10 mm Hg | >10 mm Hg |
| VTI Prosthesis / VTI LVOT | <2.2 | 2.2–2.5 | >2.5 |
| Effective Orifice Area | ≥2.0 cm² | 1.0–2.0 cm² | <1.0 cm² |
| PHT | <130 ms | 130–200 ms | >200 ms |
For a mitral prosthesis, the mean gradient is interpreted only in conjunction with heart rate and stroke volume. Tachycardia, hypervolemia, anemia, and significant mitral regurgitation can increase the gradient without true obstruction. PHT is useful as an additional indicator but depends on the compliance of the left atrium and ventricle, so it should not be the sole criterion.
Prosthetic Regurgitation: Central and Paraprosthetic
Physiological washing jets of mechanical prostheses are short, narrow, and typical for the valve design. Pathological regurgitation can be transprosthetic due to leaflet damage, thrombosis, pannus, or endocarditis, and paraprosthetic due to suture defect or dehiscence. Acoustic shadowing from the prosthesis often underestimates the jet on TTE, so TEE is key for localizing, assessing the extent of the defect, and planning closure of the paraprosthetic fistula.
For TAVI, central regurgitation, paravalvular regurgitation, eccentric multiple jets, and the impact of native ring calcium are separately assessed. Quantitative assessment should combine color Doppler, CW/PW Doppler, reverse diastolic flow in the aorta, and, if necessary, CT or MRI.
Structural and Non-Structural Dysfunction
ASE 2024 suggests thinking not only in terms of “stenosis” and “regurgitation” but through the mechanism of dysfunction. Structural degeneration is internal damage to the bioprosthesis: calcification, rupture, thickening, or restriction of leaflets. Non-structural dysfunction is a problem without primary leaflet damage: patient-prosthesis mismatch, paraprosthetic regurgitation, malposition, frame deformation, pressure recovery.
Prosthesis thrombosis may present with a sudden increase in gradient, leaflet thickening, and reduced mobility. Pannus often forms gradually and is better seen on CT as dense tissue around the seating ring. Endocarditis is suspected with new regurgitation, vegetation, abscess, or dehiscence; TEE and in certain scenarios PET/CT increase diagnostic confidence.
Patient-Prosthesis Mismatch
Patient-prosthesis mismatch means that a normally functioning prosthesis is too small for the body surface area, resulting in a high residual gradient immediately after surgery. For the aortic position, ASE 2024 uses indexed effective orifice area: with BMI <30 kg/m², absence of significant mismatch is >0.85 cm²/m², moderate is 0.66–0.85 cm²/m², severe is ≤0.65 cm²/m². With BMI ≥30 kg/m², the thresholds are lower: >0.70, 0.56–0.70, and ≤0.55 cm²/m², respectively.
The key sign of PPM is a high gradient already on the initial postoperative EchoCG with normal leaflet morphology and mobility. A progressive increase in gradient over months or years more often corresponds to thrombosis, pannus, or structural degeneration.
When TEE, CT, MRI, or PET is Needed
TEE is indicated for unclear regurgitation, suspected endocarditis, mitral prosthesis thrombosis, paraprosthetic fistula, and dehiscence. CT is especially useful for TAVI: it assesses frame expansion, ellipticity, malposition, pannus, thrombosis, and hypoattenuated leaflet thickening. MRI is used for quantitative assessment of regurgitation when EchoCG is limited by artifacts. PET/CT is considered for suspected prosthesis infection if echocardiographic data are inconclusive.
Practical Conclusion Algorithm
- Specify the model, size, position of the prosthesis, and implantation date; for TAVI, the device type and presence of valve-in-valve.
- Compare with early baseline: gradient, DVI, EOA, degree of regurgitation.
- Check for technical errors: incorrect LVOT, unmaximized velocity, mismatch of heart rate and rhythm.
- Determine hemodynamic phenotype: normal function, obstruction, regurgitation, PPM, or high flow.
- Describe the likely mechanism and recommend a method for clarification: TEE, CT, MRI, or PET/CT.
The phrase “prosthesis dysfunction” without a mechanism is of little help to the clinician. An optimal conclusion contains the degree of impairment, probable cause, assessment reliability, and specific next step.
Frequently asked questions
Can a mean gradient ≥20 mm Hg after TAVI be considered stenosis?
No, an isolated gradient does not equal stenosis. It is necessary to consider the TAVI model and size, baseline, DVI, EOA, AT, flow, and presence of regurgitation. For accurate norms, ASE 2024 recommends using model- and size-specific references.
How to distinguish obstruction of an aortic prosthesis from patient-prosthesis mismatch?
In PPM, a high gradient is present already on the early postoperative EchoCG, leaflets function normally, and indexed EOA is small. In obstruction, there is usually an increase in gradient relative to baseline, a decrease in DVI, a prolongation of AT, and a change in the Doppler contour.
When is TEE mandatory for a prosthesis?
In cases of suspected paraprosthetic regurgitation, dehiscence, endocarditis, mitral prosthesis thrombosis, and unclear severity of regurgitation on TTE. TEE better shows the ring, leaflets, and defect localization.