(BQ) Part 2 book Practical manual of echocardiography in the urgent setting presents the following contents: Prosthetic heart valves, the great vessels, evaluation of the pericardium, specialty echocardiographic examinations, common artifacts, hommon artifacts, chest pain syndrome,...
Prosthetic heart valves Karthik Gujja1 and Vladimir Fridman2 Division of Cardiology, Department of Internal Medicine, Long Island College Hospital, New York, USA Cardiovascular Diseases, New York, NY, USA chapter Prosthetic heart valves add another level of complexity to the performance of an echocardiogram There are multiple different types and multiple different echocardiographic signatures of prosthetic valves Furthermore, many forms of prosthetic valve malfunction exist, and in some cases these are life threatening and must be diagnosed immediately The types of prosthetic valves/valve repairs are: •• mechanical valves •• tissue (biological) valves •• valved conduits •• annular rings There are multiple mechanical valves available on the market Some of the most common types and their characteristics are: •• Bileaflet tilting disc valves two pyrolytic carbon semicircular discs attached to a rigid valve ring by small hinges; opening angle 75–90°; three orifices: one small central and two larger lateral orifices; Normal regurgitant volume of 5–10 ml •• Single tilting disc valves circular sewing ring; circular disc eccentrically attached by metal struts; opening angle 60–80°; flow occurs through major and minor orifices •• Ball-in-cage valve circular sewing ring; silastic or metal ball; Practical Manual of Echocardiography in the Urgent Setting, First Edition Edited by Vladimir Fridman and Mario J Garcia © 2013 John Wiley & Sons, Ltd Published 2013 by John Wiley & Sons, Ltd 129 130 | Chapter Figure 7.1 Mechanical valves and their echocardiographic images with normal regurgitation profiles: top – bileaflet; middle – single leaflet; bottom – ball and cage valves (Reproduced from [1], with permission from Elsevier) cage with arches; profile; flow occurs around the ball; normal regurgitant volume of 2–5 ml The common mechanical prosthetic valves, and their normal regurgitation profiles, are shown in Figure 7.1 There are multiple types of tissue valves as well Some basic characteristics are: •• Stented heterograft valves sewing ring with three semirigid stents or struts; trileaflet – opens to a circular orifice; suboptimal hemodynamic profile compared to native valves; normal regurgitant volume of about 1 ml; 10% exhibit a small degree of regurgitation by color flow imaging •• Stentless heterograft valves manufactured from intact animal aortic valves; usually in the aortic position; no rigid stents present – larger effective orifice area; better hemodynamic profile compared to stented biological valves high Prosthetic heart valves | 131 Figure 7.2 Common bioprosthetic valves and their echocardiographic features in diastole (middle) and systole (right): top – stented; middle – stentless; bottom – percutaneous valves (Reproduced from [1], with permission from Elsevier) •• Homograft valves antibiotic-sterilized, cryogenically preserved, valves harvested from human cadavers; favorable hemodynamics, resistant to infection, no anticoagulation requirement; usually implanted as a complete root replacement with coronary artery reimplantation •• Autograft valves (Ross procedure) native pulmonary valve replaces the diseased aortic valve (the native pulmonary valve is thus the autograft); stentless homograft is placed in the pulmonary position; •• Percutaneous valves recently, valve replacements – pulmonic and aortic valves – have been done percutaneously via transapical or transfemoral approaches; imaging and hemodynamic characteristics are similar to those of stentless biological valves Some common bioprosthetic valves and their echocardiographic features are shown in Figure 7.2 132 | Chapter Echocardiographic approach to prosthetic heart valves •• Evaluation is similar to that of native valves •• Reverberations and shadowing play a significant role •• Fluid dynamics of each specific valve prosthesis influences the Doppler findings For all valve types, it is important to a complete echocardiogram, including all necessary measurements Careful attention should be given to all the hemodynamics of any prosthetic valve However, it is important to note that just because a patient has a prosthetic valve, it does not mean that their clinical situation is due to the malfunction of the valve Echo measurements for all prosthetic valves [1]: 1 Complete 2D imaging, all standard views 2 Calculate transvalvular pressure gradient – CW is usually needed to prevent aliasing 3 Calculate valve orifice area •• dependent on location of valve; •• similar to measurements of native valve in the respective position; •• can use: continuity equation; pressure half time; dimensionless index (velocity based) 4 Estimate degree of regurgitation 5 Check if the regurgitation occurs within the contours of the valve, or outside of the valve (paravalvular leak) 6 Assess ventricular size and function 7 If any post-valve replacement echo study exists, the current results MUST be compared to that study to check for any changes in hemodynamics/structures Normal echocardiographic appearance of prosthetic valves includes [1]: •• Tissue valves stented valves – three cusps and struts with echogenic sewing ring; stentless valves – thickening of aortic root/annulus, as usually in aortic position; homograft/autograft – increased echogenicity at the annular level •• Mechanical valves ball-in-cage: MMhighly echogenic; MMmotion of ball is visible; single tilting disc – a single disc is seen moving with systole and diastole; Prosthetic heart valves | 133 Table 7.1 Prosthetic aortic valve Doppler parameters (Reproduced from [1], with permission from Elsevier) Parameter Normal Possible stenosis Suggests significant stenosis Peak velocity (m/s) 4 20–35 >35 ≥0.30 0.29–0.25 1.2 1.2–0.8 2.2; PHT >130 ms Of note, high peak prosthetic mitral valve velocity without an elevated PHT likely represents increase flow through the valve, and not prosthetic valve stenosis Valve–prosthesis patient mismatch •• This is a condition where the effective orifice area of a prosthetic valve is less than that of a normal native valve for a specific patient It occurs due to a sizing problem in the operating room, when a valve smaller in diameter rather than an appropriate valve for a patient’s body surface area is placed The condition results in high gradients, even though there is no pathological condition occurring within the prosthetic valve [3, 4] •• For a specific body surface area, the valve–prosthesis patient mismatch occurs if: aortic valve: