Surgical prosthetic valves





Prosthetic valves



Fig 5.1


Flow chart of perioperative assessment of prosthetic valves. CFD, color flow Doppler; PWD, pulsed wave Doppler.

(From Oxorn D, Intraoperative Echocardiography, Elsevier, 2012; p. 97, fig. 5-1 .)






Normal valves



Bioprosthetic aortic valve



Fig 5.2


Example of insertion of normal stented bioprosthetic valve in aortic position.

(From Sellke, Rule. Atlas of Cardiac Surgical Techniques, Saunders Elsevier, 2010.)



Fig 5.3


Sutures have been placed at equidistant intervals in sewing ring and aortic annulus (left panel). Valve is lowered into position before the sutures are tied. (Perimount bovine pericardial valve, Edwards Lifesciences, Irvine, California.) With the valve-holding device removed, three struts (also known as posts or stents) at commissures of valve are easily visible (right panel) . Note that height of struts parallels normal anatomy of native aortic valve, with valve commissures more cephalad than valve sewing ring, resulting in typical curvature of valve leaflets. Normal overlap between leaflets in closed position is greatest adjacent to commissures and least in center of valve.



Fig 5.4


Short-axis (A) and long-axis (B) TEE views of aortic bioprosthesis show three struts in short axis and two struts in long axis (arrows) with thin leaflets in closed position in diastole.



Fig 5.5


In systole, short-axis (A) and long-axis (B) TEE views show open leaflets during ventricular ejection. Acoustic shadowing from the strut prevents visualization of the noncoronary leaflet in short axis (arrow) .



Fig 5.6


In another patient with similar prosthesis, 3D TEE from ascending aortic perspective shows cusps named according to position of native valve.



Fig 5.7


In this 3D multiplanar reconstruction of valve in Fig 5.6 , upper right frame shows green and blue planes intersecting LCC/RCC and NCC/RCC. These are seen in long axis in upper left and lower left frames, respectively. The arrow indicates the position of the LMCA.



Fig 5.8


Self-expandable Perceval© valve (Sorin Group, Milan, Italy), unlike transcatheter aortic valve implantation (TAVR), is placed operatively via aortotomy. Ratio of effective orifice area to diameter of sewing ring is larger relative to other tissue prostheses. Image is of collapsed valve just before implantation.



Fig 5.9


In left panel, initial valve deployment has been accomplished, and inflatable balloon placed to facilitate expansion of annular ring. Right panel shows valve fully deployed.



Fig 5.10


Midesophageal short-axis view of valve in diastole. No aortic regurgitation is visible.



Fig 5.11


Corresponding midesophageal long-axis images.



Fig 5.12


From midesophageal short-axis view of valve, with slight probe rotation, upper end of deployment apparatus is visible (white arrow; black arrow in inset).



Fig 5.13


Valve on midesophageal 3D TEE from aortic perspective. The black arrow indicates the LMCA.




Comments


The two major categories of prosthetic valves are tissue valves and mechanical valves. Bioprosthetic (or tissue) valve leaflets are fashioned from bovine pericardium or a porcine aortic valve. The leaflets are supported by a rigid ring around the annulus with metal or polymer stents that support the commissures of the valve leaflets or by the cylindrical stent of the self-expandable valve. Implantation of these “stented” bioprostheses involves sewing an appropriately sized valve into the annulus, with the valve height and symmetry ensured by the annular ring and struts. In contrast, stentless tissue valves are supported only by a cylinder of flexible fabric or tissue. Implantation of stentless valves involves placement and suturing both at the annulus, and at the top of the commissures at the appropriate height.


Tissue valves open with a central circular orifice with a valve opening and closing motion similar to a native trileaflet aortic valve. However, the antegrade velocities (and pressure gradient) are higher than expected for a native valve because the sewing ring reduces the effective orifice area. At smaller valve sizes, the degree of functional stenosis can be significant, with a smaller effective orifice area than a similar-size mechanical valve. Thus the optimal valve choice in each patient depends on the size of valve that can be implanted, in addition to considerations of valve durability and long-term anticoagulation. If the implanted valve is too small for the patient size, patient-prosthesis mismatch (defined as an indexed effective valve area <0.85 cm 2 /m 2 ) is associated with increased short-term mortality and suboptimal long-term outcomes.


Echocardiographic evaluation of the prosthetic valve after implantation should follow a standard format as shown in Fig 5.1


Suggested reading




  • 1.

    Yoganathan AP, Raghav V. Fluid dynamics of prosthetic valves. In Otto CM, editor: The practice of clinical echocardiography, ed 5, Philadelphia, 2016, Elsevier.


  • 2.

    Maslow AD, Bert AA: Echocardiographic evaluation of prosthetic valves. In Oxorn D, editor: Intraoperative echocardiography. Practical echocardiography series, Philadelphia, 2012, Elsevier, pp 95–130.




Bioprosthetic mitral valve



Fig 5.14


Stented mitral bioprosthesis (Medtronic Mosaic Mitral Prosthesis, Minneapolis, Minnesota), attached to holder, is seen from lateral view (left) and from ventricular aspect of valve (right) with leaflets in open position. Blue sutures maintain shape of prosthesis and provide orientation but are removed at time of implantation.



Fig 5.15


With valve implanted, four-chamber TEE view shows sewing ring, struts, and valve leaflets in systole. There are prominent acoustic shadows from sewing ring on 2D image (left). Color Doppler (right) shows no mitral regurgitation.



Fig 5.16


TEE midesophageal long-axis view shows one of the mitral struts protruding into the LVOT (arrow) . On the right, color Doppler shows no evidence of systolic signal aliasing, implying laminar, unobstructed flow (arrow) . Although this 2D image suggests LVOT obstruction, in most instances, there is enough room around the strut to allow unobstructed flow.



Fig 5.17


This image from different patient is 3D image from LA perspective. Black arrows indicate three leaflets, and red arrow, sewing ring (left frame). In right frame, valve is now seen from LV perspective, with visualization of three struts (white arrows). Each strut supports edge of two of three leaflets.




Comments


In the mitral position, mechanical valves are often used, as many of these patients are on chronic anticoagulation for atrial fibrillation. When bioprosthetic valves are used, stented valves are needed, rather than stentless valves, given the anatomy of the mitral annulus and left ventricle. The appearance of the valve in the mitral position is similar to a native aortic valve, with the stents protruding into the LV outflow tract. In the absence of a small and hypertrophied left ventricle, the stents rarely produce outflow tract obstruction ( Fig 5.16 ). The flow through the mitral prosthesis is similar to a normal mitral valve, with an early diastolic peak (E-velocity), normal deceleration time and an atrial velocity peak (A-velocity) if the patient is in sinus rhythm. Velocities are only slightly higher than for a native valve, due to the large effective valve area and low left atrial to left ventricular pressure gradient in diastole.


Suggested reading




  • 1.

    O’Gara PT: Prosthetic heart valves. In Otto CM, Bonow RO, editors: Valvular heart disease, ed 4, Philadelphia, 2014, Elsevier, pp 420–438.




Bioprosthetic tricuspid and pulmonic valves



Fig 5.18


Surgical view of tricuspid valve bioprosthesis from right atrial side.



Fig 5.19


In four-chamber orientation at 0-degree rotation, tricuspid bioprosthetic sewing ring and struts are seen. Valve leaflets close at slight angle in systole (left) with no detectable regurgitation on color Doppler (right).



Fig 5.20


Transgastric short-axis view of tricuspid bioprosthesis shows three struts (arrows) and closed leaflets in systole.



Fig 5.21


3D TEE of tricuspid valve from RA perspective (left) and from RV perspective (right). White arrow indicates a strut.



Fig 5.22


In a different patient, from high esophageal window, prosthetic pulmonic valve is seen; red arrow indicates one of valve struts. White arrow indicates small jet of pulmonic regurgitation.



Fig 5.23


In a 3D TEE image corresponding to Fig 5.22 , pulmonic prosthesis is seen from aspect of main pulmonary artery in systole (left), and in diastole (right). Three struts (red arrows) are more clearly visible.




Comments


Replacement of right-sided valves is less common than left-sided valves in adults. Mechanical valves in the tricuspid position have a high rate of valve thrombosis, whereas tissue valves have rapid valve deterioration. Thus tricuspid valve repair is preferred whenever possible. Bioprosthetic tricuspid valves have an appearance and flow dynamics similar to a mitral bioprosthesis. A small degree of central regurgitation is normal with bioprosthetic valves in any position, although not seen in this case.


Suggested reading




  • 1.

    Lin G, Bruce CJ, Connolly HM: Diseases of the tricuspid and pulmonic valves. In Otto CM, Bonow RO, editors: Valvular heart disease, ed 4, Philadelphia, 2014, Elsevier, pp 375–395.




Bileaflet mechanical mitral valve



Fig 5.24


Bileaflet mechanical mitral valve as it would appear from left atrial side of valve. In left panel, valve is in diastolic position with leaflets open. Two semicircular occluders (or leaflets) are free at edges, with attachment only at small “hinges” near center of valve ring. Sewing ring is covered with cloth to allow attachment of sutures. In right panel, valve is almost completely closed; full closure would occur in systole.



Fig 5.25


In patient at left, mitral valve has been implanted in “anatomic” position, with location of two prosthetic valve occluders matching normal positions of native anterior and posterior mitral valve leaflets. Bottom left panel shows “surgeons view”—view surgeon would have from right side of operating table with left atrium open—with red line intersecting valve, resulting in reconstructed 2D midesophageal long-axis view seen in top left image. Leaflets close symmetrically and are indicated with white arrows. In patient on right, valve has been implanted in “antianatomic position” with prosthetic valve occluders oriented at about 90 degrees from positions of native valve leaflets. In 3D image (lower right), green line now intersects valve symmetrically, resulting in a similar reconstructed 2D image (top right) . In the videos, examples of how the valve looks at different transducer angles is shown.



Fig 5.26


In two-chamber view, standard 2D (left) and color Doppler ( right ) images of valve shows parallel alignment of open leaflets (arrows) in diastole (top). In systole (bottom), closed leaflets are at slight angle to each other. Note shadows cast by sewing ring and reverberations due to disk occluders that obscure left ventricle in this view. Color Doppler (right) shows normal antegrade flow through narrow central orifice and larger lateral orifices in diastole (top) with typical small eccentric jets due to closure of leaflets (“cleaning” jets) in systole (bottom). Small paravalvular jet outside sewing ring is also seen—this closed spontaneously, shortly after separating from cardiopulmonary bypass.



Fig 5.27


3D color Doppler of mitral valve from left atrial perspective shows three jets of inflow in diastole (left, white arrows) and multiple washing jets during systole (right, red arrows) .



Fig 5.28


Portable AP chest radiograph shows open bileaflet mechanical valve in mitral position.



Fig 5.29


Bileaflet valve after insertion, viewed via open left atrium.




Comment


The most common type of mechanical valve is a bileaflet valve with two semicircular leaflet occluders or a tilting disk valve with a single circular occluder that pivots on hinges or a central strut. Older mechanical valve types, such as ball-in-cage valves now are rarely seen. The normal fluid dynamics of bileaflet mechanical valve prosthesis are characterized by a small amount of regurgitation due to the closure of the valve occluders. With a bileaflet valve, there are typically two converging jets from the pivot points, a small central jet, and a variable number of peripheral jets, with little signal aliasing. In addition, these normal regurgitant jets are small in size, originating from within the sewing ring.


In contrast, pathologic regurgitation occurs in unexpected locations, often paravalvular, and is usually associated with larger, more eccentric jets. Prosthetic valve regurgitation is evaluated using the same approaches as for native valves, including measurement of the vena contracta width, evaluation of the intensity and shape of the continuous wave Doppler curve, and calculation of regurgitant volume and orifice area. However, evaluation of prosthetic valves, particularly in the mitral position, requires transesophageal imaging because shadowing and reverberations from the prosthesis preclude evaluation from the transthoracic approach. Detection of the proximal isovelocity surface area (PISA) on the ventricular side of the valve is helpful for identification of the origin of the regurgitant jet, but measurements are often difficult due to PISA asymmetry and poor image quality.


Suggested reading




  • 1.

    Pibarot P: Prosthetic valve dysfunction: echocardiographic recognition and quantitation (including paravalvular regurgitation and closure) In Otto CM, editor: The practice of clinical echocardiography, ed 5, Philadelphia, 2016, Elsevier.


  • 2.

    Beigel R, Siegel RJ: Evaluation of prosthetic valve dysfunction with the use of echocardiography, Rev Cardiovasc Med 15(4): 332–350, 2014.


  • 3.

    Hahn RT: Mitral prosthetic valve assessment by echocardiographic guidelines, Cardiol Clin 31(2):287–309, 2013.




Bileaflet mechanical aortic valve


Example of a normal bileaflet mechanical aortic valve replacement. Compared with the bileaflet valve in the mitral position, the valve in the aortic position is flipped on its vertical axis.



Fig 5.30


Mechanical valve is positioned in holder, with only sewing ring of valve visible. Sutures have been placed equidistant around sewing ring for attaching prosthesis to aortic annulus.



Fig 5.31


Bileaflet valve in aortic position with forceps opening two leaflets. Note narrow slit-like central orifice and two larger semicircular orifices.



Fig 5.32


In view similar to surgical view, this echocardiographic short-axis view of aortic valve at 31-degree rotation shows two leaflets open in systole (arrows) with central slit-like orifice and two larger semicircular orifices anteriorly and posteriorly.



Fig 5.33


Long-axis view at 135 degrees. In real time, normal leaflet motion is seen with some shadowing and reverberations by proximal aspect of valve. Color Doppler (right) shows small amount of regurgitation (arrow), as expected for this valve type.



Fig 5.34


Transgastric apical view of left ventricle (LV) and ascending aorta in long-axis view shows bileaflet valve in aortic position in diastole (A) and systole (B). Note that in normal closed position, leaflets (arrow, left) are at slight angle to each other whereas open leaflets (arrow, right) assume parallel orientation. Color Doppler (C) shows two normal “washing jets” (arrows) .



Fig 5.35


With sterile transducer placed epicardially during surgery on ascending aorta, this view of aortic prosthesis was obtained. Closed leaflets (arrows) are at slight angle, as seen in apical view.



Fig 5.36


This 3D TEE midesophageal from left atrial perspective illustrates two problems when imaging mechanical valve from midesophageal position-lots of artifacts (white arrow) arising from mechanical leaflet (red arrow), and inability to assess leaflet motion, which may be more readily accomplished from transgastric position ( Fig 5.34 ).




Comments


The bileaflet valve consists of two pyrolytic carbon disks attached to a rigid ring by two small hinges. This design results in a small central slit-like orifice and two larger lateral semicircular orifices when the valve is open. As for tissue valves, the hemodynamics of a normally functioning mechanical valve are inherently stenotic, compared with a normal native valve, with tables available listing the expected transvalvular velocities, pressure gradients, and expected orifice areas for each valve type and size. Even higher velocities may be recorded with normally functioning valves due to the fluid dynamics of the central slit-like orifice. Effective orifice areas can be calculated using the continuity equation, as for native valves. Because the velocity and pressure gradient across a prosthesis valve depend on transvalvular flow rate, as well as valve type and size, a baseline examination when valve function is clinically normal is useful for distinguishing valve stenosis from normal hemodynamics on serial examinations.


Suggested reading




  • 1.

    Blauwet LA, Miller FA Jr: Echocardiographic assessment of prosthetic heart valves, Prog Cardiovasc Dis 57(1):100–110, 2014.


  • 2.

    Eleid MF, Thomas JD, Nishimura RA: Increased prosthetic valve gradients: abnormal prosthetic function or pressure recovery? Catheter Cardiovasc Interv 84(6):908–911, 2014.




Bileaflet tricuspid and pulmonic valves



Fig 5.37


Lateral chest radiograph in this patient demonstrates sewing ring of both prosthetic pulmonic and prosthetic tricuspid valve. Epicardial pacing leads and sternal closure wires are also seen.



Fig 5.38


Intraoperative view from right atrium of mechanical valve being sutured into tricuspid annulus. Note that sutures are passed through small rectangular pledgets (near tip of surgeon’s finger) to secure valve to annulus. These pledgets can sometimes be seen on echocardiography.



Fig 5.39


In (A), midesophageal four-chamber view at 0 degrees demonstrates mechanical valve in tricuspid position in diastole with leaflets open (arrows). In (B), color Doppler in short-axis view at 59-degree rotation shows normal antegrade flow across valve.



Fig 5.40


In same two views as in Fig 5.39 , closed valve leaflet and normal prosthetic regurgitation (arrows) are seen.



Fig 5.41


In high esophageal position at 130 degrees, bileaflet mechanical pulmonic valve is seen closed in diastole ( A , arrows ) and open in systole ( B , arrows ).

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Jan 2, 2020 | Posted by in CARDIOLOGY | Comments Off on Surgical prosthetic valves

Full access? Get Clinical Tree

Get Clinical Tree app for offline access