Prosthetic Valves II John N. Hamaty, DO, FACC, FACOI
Question 1For each of the following four images, the valve shown is:A. Bileaflet mechanical valveB. Mechanical valve, unknown typeC. Stented prosthetic valveD. Stentless bioprosthetic valveE. Normal native valve
Answer – 1A Answer – 1B Stented bioprosthetic valve Mechanical Valve, Unknown Type This apical 4-chamber view shows a mechanical mitral valve with extensive reverberations and shadowing distal to the valve, obscuring the LA in an 85 year old woman who had undergone valve surgery 10 years ago. The exact valve type cannot be discerned on this still frame image, but it is most likely a “low-profile” valve (bileaflet or single tilting disc) rather than a ball and cage valve, which protrudes further into the LV cavity. This is a zoomed image of an aortic valve prosthesis in the parasternal short-axis view in an 82 year old woman who underwent valve replacement for severe aortic stenosis 4 years ago. Three struts of the valve are seen at the perimeter of the valve with thin leaflets between the struts, consistent with the typical appearance of a bioprosthetic stented aortic valve.
Answer – 1C Answer – 1D Bileaflet mechanical valve Stentless bioprosthetic valve This zoomed parasternal long-axis diastolic image of the aortic valve might be mistaken for a normal appearance of the aortic valve leaflets. However, there is increase echodensity in the paravalvular region, both anteriorly and posteriorly, consistent with the extra tissue of a stentless bioprosthetic valve. This image emphasizes the importance of complete and correct clinical information for interpretation of echocardiographic data, as this patient was known to have a stentless aortic bioprosthesis. This TEE image recorded in the 2-chamber plane (note the image plane rotation angle and the LA appendage) shows the typical appearance of a bileaflet mechanical valve. The disks are closed in systole, forming a “tent-shaped” closure within the sewing ring. Distal to the valve the LV is obscured by shadowing from the sewing ring and reverberations from the valve disks. The small dense echo on the atrial side of the medial aspect of the sewing ring most likely is a valve suture.
Question 2 This 44 year old male presented for evaluation of atypical chest pain. He had undergone aortic valve replacement for aortic regurgitation 8 years ago with placement of a 27 mm stented bioprosthetic valve. A post-operative echocardiogram demonstrated an aortic velocity of 2.4 m/s, mean transaortic gradient of 19 mmHg, and valve area of 1.5cm2 . Data from the current study are shown in the figure below. Measure the aortic valve velocity and calculate the maximum transaortic gradient and valve area.
Answer 2 Aortic Velocity -- 3.0 m/s Maximum gradient 36 mmHg Aortic valve area 1.1cm2 The aortic velocity shown is about 3.0 m/s, corresponding to a maximum transaortic pressure gradient of 4(3)2 or 36 mmHg. Calculation of mean gradient requires averaging the instantaneous pressure gradients over the systolic ejection period, so this maximum gradient cannot be compared directly with the baseline postoperative mean gradient. However, aortic velocity has increased from 2.4 to 3.0 m/s suggesting possible early prosthetic valve stenosis. This is a central flow orifice valve with anatomy similar to a native aortic valve so continuity equation valve area can be calculated. The measured LV outflow tract diameter (LVOTD), not the implanted valve size, should be used in the valve area calculation. Thus, in this example, LV outflow tract cross-sectional area (CSALVOT) is: CSA LVOT = πr2 = 3.14(2.3/2)2=4.15cm2 Aortic valve area (AVA), then is: AVA = CSA LVOT x VTILVOT / VAo = 4.15CM2 X (18CM/68CM) = 1.1CM2
Answer 2 – Continued For a quicker valve area calculation, maximum LV outflow tract and aortic velocities can be substituted for velocity-time integrals: AVA = CSA LVOT x VLVOT / VAo = 4.15CM2 X (0.8M/S/3.0M/S) = 1.1CM2 These findings suggest there has been a decrease in functional aortic valve area compared with the early postoperative study, which is consistent with early calcific degeneration of a 10 year old bioprosthetic valve in a young patient. However, this degree of stenosis is unlikely to account for symptoms of chest pain so that the evaluation for other causes is appropriate
Question 3 A 43 year old woman with aortic valve replacement 20 years ago for congenital aortic stenosis presents for routine follow-up. She is asymptomatic and physically active with no exercise limitation , but no previous echocardiogram are available. A systolic murmur is noted on examination and the echocardiogram shows the following doppler data. Exercise treadmill testing Transesophageal echocardiography Calculate continuity equation valve area Chest computed tomographic imaging LV strain rate imaging
Answer 3 3 – D This is a doppler recording of transaortic flow based on the presence of prominent valve opening and closing clicks, an ejection type velocity curve, and the time of flow relative to the QRS signal. The triangular shape of the signal suggests normal valve function because stenotic valves usually have a more rounded systolic curve with a late peaking maximum velocity. However, the velocity of 4.3 m/s is much greater than expected for this valve type. This high velocity most likely is due to low acceleration in the central slit-like orifice of the bileaflet valve with pressure recovery distally resulting in only a modest valve gradient. The denser signal within the aortic curve supports this possibility of valve thrombosis or pannus formation limited disk excursion must be excluded by direct visualization of leaflet motion. Simple fluoroscopy can be used to evaluate mechanical disk motion with careful adjustment of imaging angle to visualize the leaflets. However, chest computer tomographic imaging showed normal valve function in this patient. Exercise treadmill testing can be helpful to clarify symptoms status with native or prosthetic alve stenosis but is not needed in this asymptomatic patient. TEE might provide better images of the posterior aspects of the prosthetic valve, but shadowing and reverberations would now obscure the anterior valve structures, making it difficult6 to exclude prosthetic valve stenosis. The continuity equation valve area will be falsely reduced if the apparent aortic velocity is recorded from the small central flow orifice. LV strain rate imaging allows detection of early LV dysfunction when aortic valve disease is present but would not be helpful for evaluation of valve function in this patient
Question 4 This 88 year old woman presented with worsening heart failure and hemoptysis. She had undergone bioprosthetic mitral valve replacement 12 years ago for severe mitral stenosis with an early postoperative baseline echocardiogram that showed normal LV and RV size and function, normal prosthetic valve function, and a pulmonary systolic pressure of 40 mmHg. On exam now she has a blood pressure of 100/70 mmHg, heart rate of 74 bpm with an irregular pulse, jugular venous pressure of 20cm H2O, distant heart sounds and bilateral pulmonary rales. The following doppler tracings were recorded on the current study. The most likely cause of her current symptoms is: Pulmonary embolus LV systolic dysfunction Severe mitral regurgitation Rheumatic aortic valve disease Mitral stenosis
Answer 4 E – Mitral Stenosis These doppler recordings show a high velocity tricuspid regurgitant jet, consistent with pulmonary hypertension, and a transmitral flow signal consistent with an elevated transmitral gradient and small valve area. The tricuspid regurgitant signal is identified based on systolic flow with a long flow period relative to the QRS and with the typical rapid, followed by slow, rate of rise in velocity with a late peaking curve. The transmitral flow curve is in diastole with a typical passive flow pattern or an early diastolic peak and linear fall off in velocity through diastole. Atrial fibrillation is present with no discernable A-velocity. The slow diastolic decline in velocity is consistent with mitral stenosis. Pulmonary embolus might be associated with pulmonary hypertension, but transmitral flow would be normal. LV systolic dysfunction would result in a reduce dP/dton the mitral regurgitant velocity signal, which is not shown here. Severe mitral regurgitation would result in an increased antegrade transmitral velocity, but the diastolic slope would be steep. Rheumatic aortic valve disease is present in about a third of patients with rheumatic valve disease, and the mitral stenosis signal appears similar in shape to aortic regurgitation. However, diastolic velocities are lower across the mitral valve compared with the aortic valve; with a diastolic blood pressure of 70 mmHg, the initial diastolic velocity for aortic regurgitation would be about 4 m/s.
Question 5 88 year old withworsening heart failure and hemoptysis. Bioprosthetic mitral valve replacement 12 years ago for severe mitral stenosis.Baseline echocardiogram that showed normal LV and RV size and function normal prosthetic valve function. Pulmonary systolic pressure of 40 mmHg Current Exam: Blood pressure of 100/70 mmHg Heart rate of 74 bpm with an irregular pulse Jugular venous pressure of 20cm H2O Distant heart sounds Bilateral pulmonary rales. Using the above data from question 4, calculate the following: Pulmonary systolic pressure:_____________________________________ Mitral valve area:_____________________________________________
Answer 5 Pulmonary systolic pressure 79mmHg Mitral valve area 0.6cm2 The tricuspid regurgitant velocity is 4.0 m/s, reflecting a RV-RA systolic pressure difference of 64 mmHg. Images of the inferior vena cava are not provided to estimate RA pressure; the central venous pressure was estimated to be about 20cm H2O (or 15mmhg) based on physical examination of the neck veins. The conversion factor for units of pressure is 1.36cm H2O for each mmHg. Thus, adding RA pressure to the RV-RA pressure difference, the estimated pulmonary systolic pressure is 79 mmHg. With this bioprosthetic valve, mitral valve area is calculated from the mitral pressure half-time (T ½ ), as for native mitral valve stenosis. One the first beat, the peak transmitral velocity is 2.3 m/s, corresponding to an instantaneous pressure gradient of 21 mmHg. The T ½ is measured on the time axis from this point to the point on the diastolic deceleration slope where the pressure drop is half the initial gradient. A pressure gradient of 11 mmHg corresponds to a velocity of 1.66 m/s. Finding this point on the doppler signal, drawing a vertical line to the time axis, and then measuring the time interval from peak velocity to this point, provides a T ½ of 370 ms. Mitral valve area is 220/ t ½ or 6.cm2. These findings are consistent with severe prosthetic mitral stenosis. Although tissue valve durability usually is longer in older patients, at surgery the bioprosthetic valve was severely calcified with restricted leaflet motion.
Question 6 In the patient with this echocardiographic image which of the following clinical findings is most likely present? Elevated reticulocyte Diastolic murmur S4 gallop Thrombocytopenia
Answer 6 A – Elevated reticulocyte count This is a TEE 2-chamber view of a patient with a mechanical valve prosthesis showing an eccentric paravalvular mitral regurgitant jet. Paravalvular mitral regurgitation can cause hemolysis resulting in an elevated reticulocyte count. Most often, hemolysis is well tolerated and the patient is able to maintain a relatively normal red blood cell count, although sometimes vitamin and iron supplementation. Rarely is surgical or percutaneous intervention needed to close the paravalvular leak unless there also is a large volume regurgitant flow. This patient likely has a systolic (not diastolic) murmur. A wide pulse pressure is typical for aortic , not mitral regurgitation. An S4 gallop will not be present because the electrocardiogram shows atrial fibrillation. The platelet count should be normal, although blood clotting likely is abnormal due to warfarin anticoagulation for a mechanical valve and atrial fibrillation.
Question 7 This doppler tracing obtained in a patient with prior valve surgery is consistent with all of the following EXCEPT: Aortic stenosis Aortic regurgitation Mitral stenosis Mitral regurgitation
Answer 7 D – Mitral regurgitation This cw doppler tracing shows a systolic ejection fraction velocity below the baseline (recorded from the apex) with a maximum velocity about 3 m/s consistent with mild aortic stenosis or without a prosthetic aortic valve. In diastole, mild aortic regurgitation is seen with a signal that starts with aortic valve closure and extends to aortic valve opening, with a maximum early diastolic velocity about 3.5 m/s and passive diastolic deceleration with a flat slope. Overlapping with the aortic regurgitant signal is a denser diastolic signal; that has a time delay between aortic closure and onset of flow, consistent with isovolumic relaxation period, indicating that this is transmitral flow. The peak velocity over 2 m/s and slightly prolonged deceleration slope suggest mild mitral stenosis or q prosthetic mitral valve , as was the case in this patient. There should be a time interval between the end of transmitral flow and aortic ejection, but this finding is obscured by a poor signal-to-noise ration. There is no atrial contribution to LV diastolic filling because this is a ventricular paced rhythm (see electrocardiogram) and the atrial rhythm likely is atrial fibrillation. This tracing does not show evidence of mitral regurgitation; a different doppler beam is needed for better evaluation of mitral valve function.
Question 8 A 71 year old female presented for a second opinion regarding possible aortic patient-prosthesis mismatch. She had undergone a 19 mm pericardial bioprosthetic valve replacement 2 years ago but continued to have symptoms of atypical chest pain. On physical examination she is an older anxious woman with a blood pressure of 120/80mmHg, pulse of 72 bpm, body surface area of 1.9cm2, and an aortic ejection murmur but no evidence of heart failure. Echocardiography shows a normal-appearing prosthetic valve with the following doppler data shown in the image below. The most likely diagnosis in this patient is: No prosthetic valve dysfunction Prosthetic valve stenosis Prosthetic valve regurgitation Patient-prosthesis mismatch
Answer 8 D – Patient prosthesis mismatch The doppler data show an aortic velocity of 3.0 m/s with an LV outflow tract diameter of only 1.5cm and LV outflow tract velocity of 1.4 m/s. The circular LV outflow tract cross-sectional area (CSA) is 1.77 cm2. Aortic valve area calculated with the continuity equation is: AVA = CSA LVOT x VLVOT / VAo = 1.77CM2 X (1.4M/S/3.0 M/S) = 0.8CM2 When indexed for body size: AVA = 0.8 CM2 / 1.9 M2 = 0.42 CM2/M2 These data are consistent with severe patient-prosthesis mismatch, defined as a prosthetic aortic valve indexed area less than 0.65 cm2/ m2. The reason for patient-prosthetic mismatch is the very small LVOT. Ideally, patient-prosthesis mismatch is avoided by calculating the expected valve area divided by body size before valve implantation if the expected valve area is too small, an alternate valve choice or an aortic root enlarging procedure can be considered. Once patient prosthesis mismatch is present, decision making is more difficult because correction would require another surgical procedure. Both short and long term outcomes are worse when patient-prosthesis is present, but the increase in late mortality is seen only in patients younger than age 70, patients with a body mass index less than 30 kg/m2, and those with LV systolic, dysfunction (ejection fraction < 50%).
Answer 8 – Continued This patient is older than 70, she has normal LV function and is not clear that her symptoms are related to her valve size. Her BMI is 26 kg/m2, so she may benefit from weight reduction. In addition, her transvalvular mean gradient is only 14mmHg and the LV outflow to aortic velocity ration is only 1.4/3.0=0.47, neither of which support a significant hemodynamic effect from the small valve prosthesis. Thus, although she clearly meets the definition for patient-prosthesis mismatch, there is no evidence for significant stenosis or regurgitation. In any case, this patient has declined further interventions and continues to do well with medical therapy.
Question 9 Match each of the following diagnostic issues with the most useful imaging modality Prosthetic aortic valve function Prosthetic mitral valve function Aortic graft pseudoaneurysm Aneurysm of the aortic-mitral intervavlular fibrosa Aortic valve paravalvular abscess Bioprosthetic tricuspid valve vegetation LV function with a mechanical mitral valve Transthoracic 2D imaging Transthoracic Doppler TEE 2D imaging TEE Doppler Chest computed tomographic imaging
Answer 9 Prosthetic aortic valve function: B – Transthoracic doppler Prosthetic mitral valve function: D – TEE Doppler Aortic graft pseudoaneurysm: E – Cardiac CT imaging Aneurysm of the aortic-mitral intervalvular fibrosa: C – TEE 2D imaging Aortic valve paravalvular abscess: A – Transthoracic 2D imaging Bioprosthetic tricuspid valve vegetation: A – Transthoracic 2D imaging LV function with a mechanical mitral valve: A – Transthoracic 2D imaging Evaluation of a patient with suspected prosthetic valve dysfunction often requires both transthoracic and TEE imaging. Transthoracic imaging is optimal for measurement of LV volumes and ejection fraction because the LV often is foreshortened on TEE and may be shadowed by the mitral or aortic valve prosthesis. Transthoracic imaging usually is preferred for a bioprosthetic tricuspid valve because this valve is anterior in the chest and thus well seen from this approach. However, TEE imaging maybe needed is transthoracic images are suboptimal. Transthoracic doppler is the best approach for evaluation of prosthetic aortic valve function because the doppler beam can be aligned from an apical window parallel with transvalvular flow and aortic regurgitation can be evaluated in both parasternal and apical views. In contrast, on TEE, alignment of the doppler beam with transaortic flow is problematic and evaluation of regurgitation is limited by shadowing of the LV outflow tract by the prosthetic valve. In patients with a prosthetic mitral valve, the LA side of the prosthesis is shadowed on transthoracic imaging so that the TEE is recommended whenever prosthetic mitral regurgitation is suspected. Similarly, TEE is much more sensitive than paravalvular abscess because it allows imaging of the LA side of the aortic and mitral valve prosthesis. Of course, an anteriorly located aortic paravalvular abscess may be seen on transthoracic imagine, but absence of an anterior abscess does not exclude posterior annular infection. With involvement of structures outside the narrow window provided by echocardiographic imaging, such as an aortic root pseudoaneurysm, wide field imaging modalities, such as chest computed tomography, are recommended.
Question 10 The echocardiographic image below was obtained on the postoperative baseline study after bioprosthetic mitral valve replacement. Which is the most likely diagnosis for the structure indicated by the arrow: Vegetation Valve strut Mitral valve Ruptured papillary muscle LC thrombus
Answer 10 C – Mitral valve This image shows the native mitral valve chords and part of the mitral leaflet, which were retained at the time of mitral valve replacement. Maintenance of mitral annular– papillary muscle continuity helps prevent loss of LV systolic contractile function with surgical mitral valve replacement. Typically the prosthetic valve is inserted centrally and the posterior leaflets and chords are left connected to the papillary muscle behind the prosthetic valve sewing ring. The anterior leaflet may be partially retained or may be resected, leaving freely mobile chordal remnants. A mitral vegetation would be more likely on the LA side of the valve; infection of the sewing ring with annual abscess formation instead of a typical vegetation is common with a prosthetic valve. Valve struts are more uniform in appearance and do not protrude this far into the LV cavity. A ruptured papillary muscle results in a disrupted muscle head moving freely in the LV, attached to the mitral valve; normal attachments of the chords to the papillary muscle can be seen on this image . An LV thrombus usually occurs in an area of regional dysfunction, often the apex, and is adherent to the LV myocardium.
Question 11 This 75 year old man underwent surgical aortic valve repair 10 years ago for endocarditis resulting in prolapse of the noncoronary cusp. He has done well postoperatively and has been followed annually with echocardiograms showing mild to moderate residual aortic regurgitation. He now presents with a cough, fatigue, and a low grade fever. On exam his blood pressure is 158/40 mmHg, pulse is 113 bpmand irregular; bibasilar rales are present. The doppler flow tracing below was recorded. The most likely new diagnosis in this patient is: Acute mitral regurgitation Aortic to LA fistula Severe pulmonary hypertension Severe aortic stenosis Patent ductus arteriosis
Answer 11 A – Acute mitral regurgitation This doppler tracing shows a diastolic signal with a peak velocity and systolic slope consistent with known aortic regurgitation The diastolic flow is directed away from the transducer, so the probe position likely is parasternal with a posteriorly directed aortic regurgitant jet. In systole there is an ejection-type (rapid rise and fall with curved wave-form) signal with a peak velocity about 5.5 m/s. This is most consistent with mitral regurgitation, given a systolic blood pressure of 158 mmHg even with an LV pressure of 20mmHg., the Bernoulli equation indicates that velocity should be at least 6 m/s if the intercept angle between the jet and ulatrasound beam was parallel. In this example, a nonparallel intercept angle is most likely with the transducer in a parasternal position. The relatively rapid fall-off in velocity in late systole suggests acute regurgitation with an elevated LV pressure. This patient had a mitral valve vegetation with an adjacent leaflet perforation and blood cultures were positive for alpha-hemolytic Streptococcus. With an aortic-to-LA fistula, high velocity continuous flow in systole and diastole would be seen reflecting the high aortic-to-LV pressure difference. The typical valve velocity curves would not be seen. Pulmonary hypertension cannot de diagnosed from these data; a tricuspid regurgitant jet would be longer in duration and overlap with aortic regurgitation at the onset and end of flow. If the systolic signal were due to aortic stenosis, a slight time interval before and after aortic regurgitation would be seen corresponding to the isovolumic relaxation and contraction periods. A patent ductus arteriosis would show continuous flow in the pulmonary artery with a lower velocity, reflecting the pressure difference from the descending aorta to the pulmonary artery, and the distinct valve-type curves would not be seen.