Recommendations for Imaging Prosthetic Heart Valves
- Lancellotti P, Pibarot P, Chambers J, et al.
- Recommendations for the Imaging Assessment of Prosthetic Heart Valves: A Report From the European Association of Cardiovascular Imaging Endorsed by the Chinese Society of Echocardiography, the Inter-American Society of Echocardiography, and the Brazilian Department of Cardiovascular Imaging. Eur Heart J Cardiovasc Imaging 2016;17:589-590.
This manuscript summarizes current recommendations for the evaluation of prosthetic heart valves. The following are 10 key points to these recommendations:
- Determining the cause of prosthetic valve dysfunction is critical in the management of these patients. Imaging with transthoracic echocardiography and transesophageal echocardiography are the mainstays of imaging assessment, while other imaging modalities such as computed tomography (CT), magnetic resonance imaging (MRI), cinefluoroscopy, and nuclear imaging may play complementary roles.
- Initial and longitudinal echocardiography with multiple views are important for complete assessment of prostheses, although these can be limited by difficult windows and acoustic shadowing. Doppler and color Doppler provide important hemodynamic data, while 3D imaging can add incremental data including assessment of possible thrombus, pannus, and dehiscence that may be seen inadequately on 2D imaging.
- Mechanical valve disc excursion can be assessed by cinefluorosopy or CT. CT can also evaluate suspected ring dehiscence, distinguish pannus from thrombus, image paravalvular pathology, and measure the orifice of stenotic valves.
- Hemodynamics of prosthetic valves can be more complex than with native valves. Some mechanical prostheses will have different orifices with different hemodynamic profiles (e.g., lower velocity flow through a larger orifice and higher velocity flow through a smaller orifice).
- There are several pitfalls in measuring gradients. The simplified Bernoulli equation can overestimate the pressure gradient across a normally functioning bioprosthetic valve, and use of the full equation should be considered. Further, the peak-to-peak pressure gradient by catheterization should not be used to assess valves, and other parameters such as the peak instantaneous gradient should be used instead. Echocardiographic gradients may be underestimated by misalignment of the Doppler beam, low-flow states, and elevated systemic blood pressure. Overestimation of gradients can occur in high-flow states and the pressure recovery effect.
- The effective orifice area (hemodynamic orifice) is not the same as the geometric orifice area (valve opening area), and the former is up to 29% smaller. Calculating the effective orifice area by the continuity equation presents several challenges, including accurate measurement of the left ventricular outflow tract diameter.
- Doppler velocity index can be particularly useful in patients with prosthetic heart valves, as there is a linear relationship between the velocity in the left ventricular outflow tract and the implanted valve size. An abnormal aortic valve prosthesis typically has a value of ≤0.3.
- Structural valve dysfunction includes intrinsic valve stenosis or regurgitation. Nonstructural valve dysfunction includes valve dehiscence or interference with valve function by pannus, tissue, or suture material. Other causes of valve dysfunction include valve thrombosis, embolism, or endocarditis.
- Patient-prosthesis mismatch results from selection of a valve size that is too small for patient size, resulting in elevated postoperative gradients. This is defined by a low indexed effective orifice area, and different cutoffs should be used for obese and nonobese patients.
- Algorithms are provided to evaluate patients with elevated prosthetic valve gradients, which are defined as a peak aortic valve velocity of >3 m/s and/or a mean gradient ≥20 mm Hg, or a peak mitral early diastolic velocity ≥1.9 m/s and/or a mean gradient ≥6 mm Hg.
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