A 48-year-old woman with a previous mechanical bileaflet mitral valve replacement was diagnosed with severe mitral stenosis and moderately severe aortic regurgitation by transthoracic echocardiography. She was referred to our institution for surgical replacement of her aortic and mitral valves. Our IRB waived the requirement for patient consent for this report.
In the operating room after anesthetic induction, a transesophageal echocardiographic (TEE) midesophageal 4-chamber view confirmed an immobile mechanical mitral valve leaflet causing severe mitral stenosis (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A679). Mean transmitral pressure gradient measured with continuous wave Doppler was 19 mm Hg with a heart rate of 55 bpm. A midesophageal long-axis view with color flow Doppler demonstrated severe turbulence in the left ventricular outflow tract (LVOT) during diastole, suggesting severe aortic regurgitation (Fig. 1; Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A680). A midesophageal aortic valve short-axis view (partially cut through the LVOT) suggested aortic regurgitation (Video 3, see Supplemental Digital Content 3, http://links.lww.com/AA/A681). Significant shadowing from the mechanical mitral valve created difficulty in determining whether the jet resulted from aortic regurgitation or mitral inflow. Thus, other echocardiographic measures to differentiate the etiology of the diastolic LVOT turbulence were performed. A deep transgastric long-axis view which allowed imaging of the LVOT without shadowing from the prosthetic mitral valve demonstrated absence of turbulence proximal to the aortic valve, suggesting that LVOT turbulence did not originate from the aortic valve. Furthermore, spectral Doppler demonstrated LVOT flow, which peaked at less than 2.0 m/s and followed mitral valve opening (rather than aortic valve closing), consistent with mitral inflow (Fig. 2). Additional echocardiographic evidence inconsistent with severe aortic regurgitation was documented, including aortic valve leaflets without significant abnormalities, a normal-appearing aortic root, and absence of flow reversal in the descending aorta. These findings suggested that diastolic LVOT turbulence was related to an eccentric mitral inflow jet, rather than aortic regurgitation. The patient underwent mitral valve replacement with a 27-mm St. Jude bileaflet mechanical mitral valve (St. Jude Medical, St. Paul, MN). TEE performed after separation from cardiopulmonary bypass demonstrated a well-seated mitral valve and a competent aortic valve.
Diastolic turbulence in the LVOT related to an eccentric mitral inflow jet can masquerade as aortic regurgitation leading to inappropriate and possibly harmful treatment, including unnecessary aortic valve replacement. Thus, correct determination of the etiology of diastolic LVOT turbulence is essential. A detailed 2-dimensional and Doppler echocardiographic examination of the aortic and mitral valves can determine the true cause of diastolic LVOT turbulence.
This case demonstrates that relying exclusively on color flow Doppler to identify the cause of LVOT turbulence may lead to an erroneous diagnosis. Although color flow Doppler can delineate the origin and direction of the jet, an excessive signal, characterized by high-velocity flow in multiple directions, may obscure true jet direction. Shadowing and reverberation artifacts from the prosthetic mitral valve further complicate delineation of the jet. Furthermore, the color flow Doppler signal from an off-axis midesophageal aortic valve short-axis view incorrectly suggested severe aortic regurgitation. These challenges were overcome by several echocardiographic maneuvers. Increasing the aliasing velocity of color flow Doppler decreased the Doppler signal, allowing closer examination of the jet and identification of its origin. A deep transgastric long-axis view allowed imaging of the LVOT and aortic valve without shadowing and reverberation from the prosthetic mitral valve, where absence of turbulent flow proximal to the aortic valve was inconsistent with aortic regurgitation. Repositioning the short-axis image of the aortic valve excluded the LVOT and demonstrated competence of the aortic leaflets, emphasizing the importance of collecting this image at the appropriate level.
A spectral Doppler tracing also helped differentiate mitral inflow from aortic regurgitation. Spectral Doppler demonstrated the opening and closing “clicks” of the mitral and aortic valves, allowing accurate analysis of flow timing. A high-velocity flow signal after mitral valve opening, instead of aortic valve closure, was consistent with mitral inflow rather than aortic regurgitation. Since aortic regurgitation is characterized by longer duration and higher peak velocity averaging between 3.5 to 4 m/s, a peak velocity of spectral Doppler signal <2 m/s was consistent with mitral inflow.1 Though not seen in this case, distinct E and A waves demonstrated by spectral Doppler suggest a mitral origin of the jet.2 In addition, pulse wave Doppler can discriminate between aortic regurgitation and mitral inflow when the sample volume is positioned immediately proximal to the aortic valve, where absence of flow suggests that aortic regurgitation is unlikely. Thus, spectral Doppler provided evidence that the etiology of the LVOT turbulence was related to transmitral inflow.
It is important to note that echocardiographic findings to explain the cause of aortic regurgitation, such as annular dilation or leaflet prolapse, are necessary before the diagnosis of aortic regurgitation can be established. In this report, the TEE documented normal aortic valve leaflets and aortic annulus. Proximal flow convergence, vena contracta, and holodiastolic reversal of aortic flow were absent.3–5 Holodiastolic flow reversal in the descending aorta corroborates the presence of moderate or severe aortic regurgitation when a mitral valve prosthesis impairs visualization of the LVOT.5 Furthermore, an aortic retrograde end-diastolic flow velocity >18 cm/s measured below the aortic isthmus predicts severe aortic regurgitation and a regurgitant fraction of >40% with high sensitivity and specificity.6 In our report, these echocardiographic signs consistent with aortic regurgitation were absent (Table 1).
In conclusion, many factors can complicate identification of the source of diastolic LVOT turbulence. However, the etiology of turbulence in the LVOT can be differentiated by detailed echocardiographic examination including 2-dimensional echocardiographic images, color flow, and spectral Doppler.E
Clinician’s Key Teaching Points
By Nikolaos J. Skubas, MD, FASE, Kent H. Rehfeldt, MD, and Martin J. London, MD
- In aortic regurgitation (AR), there is a high-velocity, retrograde diastolic flow in the left ventricular outflow tract (LVOT). In a stenosed mechanical mitral valve (MS), the antegrade diastolic blood flow accelerates as it enters the left ventricle and may be directed away from the malfunctioning disk. As a result, color flow Doppler imaging of the LVOT may reveal a turbulent blood flow pattern.
- Acoustic shadowing and reverberations from a mechanical mitral prosthesis will further complicate LVOT imaging from the midesophageal position. Additional transesophageal echocardiographic views, such as the deep transgastric long-axis view, may be necessary to image the LVOT without the interference of artifacts.
- In this case of a patient with a stenosed mechanical mitral prosthesis and an immobile leaflet, a diastolic LVOT jet imaged in the midesophageal views would not initially be differentiated from significant AR. In the deep transgastric long-axis view, significant AR was excluded by the absence of a diastolic color Doppler signal at the aortic valve level and a low continuous wave Doppler jet velocity (<2 m/s) immediately after the characteristic spectral Doppler mitral prosthetic valve “opening click.” In addition, there was no diastolic flow reversal in the descending aorta, and the aortic valve and root were noted to be normal on 2-dimensional imaging.
- Multiple views, proper color Doppler settings, such as an increased Nyquist limit to decrease the area of the color Doppler signal, close attention to timing, and knowledge of expected spectral Doppler transvalvular velocities (lower in MS, higher in AR) should all be carefully considered to allow differentiation between AR and eccentric MS jets. This is important when deciding which valve is malfunctioning and when planning for the route of cardioplegic solution administration.
Name: Paul Y. Paik, DO.
Contribution: This author helped analyze the data and write the manuscript.
Attestation: Paul Y. Paik reviewed the analysis of the data and prepared the manuscript.
Name: Michelle Capdeville, MD.
Contribution: This author helped prepare and edit the manuscript and obtain echocardiograms of subject of interest.
Attestation: Michelle Capdeville reviewed the analysis of the data and prepared the manuscript.
Name: Andra E. Duncan, MD.
Contribution: This author helped design, prepare, and edit the manuscript.
Attestation: Andra E. Duncan reviewed the analysis of the data and prepared the manuscript.
This manuscript was handled by: Martin J. London, MD.
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