Prof. Philippe Pibarot,
Prosthesis with high gradient: differential diagnosis using echo and other imaging modalities (Mauro Pepi, Milan, Italy) There are several potential causes of high gradient across prosthetic valves: prosthesis dysfunction (stenosis and/or regurgitation), prosthesis-patient mismatch, and localised high velocity through the central orifice in the case of bi-leaflet mechanical valves. Prosthesis-patient mismatch is the most frequent cause of high gradient and can be identified by calculating the projected indexed effective orifice area (i.e. the normal reference value of EOA for the model and size of prosthesis implanted in the patient divided by the patient’s body surface area). According to recent studies, an acceleration time ≥100 ms appears to be superior to the criteria based on transprosthetic gradient, EOA, and Doppler velocity index in distinguishing intrinsic prosthetic valve dysfunction from PPM or central localised high velocity. However, the cornerstone of the differential diagnosis is the evaluation of leaflet morphology (leaflet thickening, calcification) and mobility (bioprosthetic and mechanical valves). TTE is often suboptimal for this purpose. TEE is superior to TTE but may lack sensitivity to detect abnormal mobility. Cinefluoroscopy is a simple, fast, non-invasive method that allows accurate detection of even minor abnormalities in leaflet mobility of mono-leaflet and bi-leaflet mechanical valves.
Prosthetic valve regurgitation: detection, localisation, and quantification (William A. Zoghbi, Houston, Texas, USA) Assessment of severity of prosthetic valve regurgitation is generally much more complex than in native valves because of the high prevalence of paravalvular regurgitation and eccentric jets. Moreover, TTE may underestimate the presence and severity of prosthetic mitral valve regurgitation because of shadowing caused by the valve components. TEE is useful to unmask this “occult” mitral prosthesis regurgitation. Given that all parameters of prosthetic valve regurgitation have important limitations and may be subject to measurement errors, a comprehensive, multiparametric approach that integrates structural (LV and LA size) as well as qualitative (diastolic flow reversal in descending aorta for aortic regurgitation), semi-quantitative (aortic regurgitant jet width, mitral regurgitant color flow jet area in LA), and quantitative (regurgitant volume and fraction by volumetric method or PISA when feasible) parameters are highly recommended. Paravalvular regurgitation is common following transcatheter aortic valve implantation (TAVI). The circumferential extent of the regurgitant jet(s) in the short-axis view may be used to estimate paravalvular regurgitation (severe when >20%). However, this parameter has not been validated in the context of TAVI and it may overestimate regurgitation severity in a substantial number of cases. The role of 3D echo and cardiac magnetic resonance (CMR) imaging in quantitating paravalvular prosthetic regurgitation is promising and needs further investigation.
Role of imaging in the diagnosis and treatment of prosthetic valve thrombosis (Patricia Reant, Bordeaux, France). Prosthetic Valve Thrombosis (PVT) is most often encountered in patients with mechanical valves and inadequate anti-thrombotic therapy. PVT may also be seen in bioprosthetic valves where it most often occurs in the early postoperative period. Pannus and thrombosis may be present alone or in combination and cause acute or subacute valve obstruction. The incidence of obstructive valve thrombosis varies between 0.3 and 1.3% per patient-year in patients with mechanical valves. If there is a clinical suspicion of PVT, echocardiography should be done promptly and include TEE, particularly if the prosthesis is in the mitral position. The most important factors to consider for therapeutic decision making are: (1) the presence of prosthetic valve obstruction; (2) the size and mobility of the thrombus; and (3) the clinical and hemodynamic condition of the patient. TEE is helpful in distinguishing thrombus from pannus and to assess size/mobility of the thrombus. In case of non-obstructive left-sided PVT in clinically stable patients, heparin therapy and repeated TEE is the recommended first line of treatment. If unsuccessful and thrombus is large (>0.8 cm2 or 5 mm) and/or mobile, surgery is recommended. In case of obstructive PVT, surgery is the preferred therapy unless patients are at prohibitive surgical risk. Role of echo in the diagnosis and management of prosthetic valve endocarditis (Jean G. Dumesnil, Québec, Canada) Prosthetic valve endocarditis is the most severe form of infective endocarditis and occurs in 1–6% of patients with valve prostheses accounting for 10-30% of all cases of infective endocarditis. Prosthetic valve endocarditis is an extremely serious condition with high mortality rates (20-50%). Echocardiography and particularly TEE plays a key role in the diagnosis of prosthetic valve endocarditis, follow-up, detection of complications and assessment of prognosis. The diagnosis relies predominantly on the combination of positive blood cultures and echocardiographic evidence of prosthetic infection, including vegetations, paraprosthetic abscesses, or a new paravalvular regurgitation. TEE is mandatory in all cases. False negative findings are more frequent than for native valve endocarditis. Hence, if the initial TEE is negative but suspicion for endocarditis remains, one should repeat within 7-10 days and/or use alternative imaging modality such as multislice computed tomography and positron emission tomography (PET). Surgery should be considered in the following situations: failure of medical treatment, hemodynamically significant prosthesis dysfunction, especially if associated with deterioration of LV function, large vegetations, paraprosthetic complications, and development of intracardiac fistulas. Recent studies suggest that early surgery may be associated with better survival compared to the conventional antiobiotics-first strategy.
Doppler-echocardiography is undoubtedly the method of choice to identify and quantitate prosthetic valve dysfunction and assess its repercussions on cardiac function. However, the particular context of prosthetic valves poses some major challenges in terms of imaging and flow dynamics that push Doppler-echocardiography to its limits. The take-home message is that a comprehensive approach that integrates several direct and indirect parameters of valve function measured by TTE and TEE is key to appropriately assess prosthetic valve function and other imaging modalities, such as cinefluoroscopy, CMR, and PET are often needed to complement or confirm the information obtained by Doppler-echocardiography.
Prosthetic valve evaluation
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