DK2985_C000 1..28 - AlSharqia Echo Club

372 Transesophageal Echocardiography(A)(B)(C)Figure 16.9 Aortic valve replacement with a stentlessFreestyle TM bioprosthesis. (A) Full root technique. After excisingthe native valve and sinus walls, the coronary arteries are excisedfrom the aorta and reattached to the buttonholes of the bioprosthesis.An end-to-end anastomosis attaches the bioprosthesis to theascending aorta. (B) Modified subcoronary technique. The noncoronarysinus of the bioprosthesis is maintained, and right andleft sinuses are scalloped. (C) Freestyle TM bioprosthesis. (A &B Courtesy of Medtronic Inc.)The next priority, after having examined the morphologyof the valve, is to determine the presence orabsence of any valvular regurgitation and its severity. Inthe case of mechanical prostheses, small jets of transvalvularregurgitation within the prosthesis may benormally observed: two in the case of tilting disk prostheses(e.g. Medtronic-Hall) or three in bileaflet prostheses(e.g. St-Jude or On-X). These jets, also known as closingvolumes, occur as the result of the normal necessaryspace between the occluder(s) and the sewing ringwithout which jamming of these parts would occur. Theinexperienced observer should not be alarmed by thesejets, which at times may even appear moderate (2þ)particularly when the jets are superimposed. Smallperivalvular jets of regurgitation may also be observedwith all types of prosthesis. In this context, it should beemphasized that echocardiography is a very sensitivetechnique and will detect even minute amounts of regurgitation.Such small jets are a frequent occurrence. Somewill significantly decrease after the injection of protaminebefore CPB weaning (28,29) and will often disappear inthe days, weeks, or months after the operation as thehealing process evolves (Fig. 16.11). More importantregurgitation is rare and is most often due to a technicalproblem after insertion of a stentless prosthesis or anhomograft. It may be either periprosthetic or centrovalvularand more than 1þ regurgitation usually requiresreturning to CPB for immediate correction (Fig. 16.12).It is not always possible to obtain accurate measurementsof intraoperative gradients and they are usuallynot necessary with mechanical prosthesis or stentedbioprosthesis as there is no immediate reason for theseprostheses to malfunction. However, such measurementsmay become more relevant in the case of stentless prostheses,homografts, or autografts especially if the twodimensional(2D) images suggest some inherent technicalproblem (e.g. perivalvular hematoma and/or crimping ofthe valve).If a high gradient is noticed in the operating room, onemust first determine whether or not it is partially or principallyrelated to a high flow velocity in the left ventricularoutflow tract (LVOT). In particular, relief of the valvularobstruction in patients operated on for AS may result insome remodeling and temporary narrowing of theLVOT. The administration of inotropic agents uponcoming off CPB may also contribute to this phenomenon.Notwithstanding these considerations, the most frequentcause of high postoperative gradients is patient–prosthesismismatch as it may occur in up to 70% of cases (7),depending on the type of prosthesis being implanted.It is much less likely to occur if the aforementioned prospectivestrategy was followed (Fig. 16.4). If not, its presencemay easily be confirmed by going through thesame algorithm after the fact, that is, dividing the reference