Echocardiography in Percutaneous Valvular Intervention

Preimplantation Assessment

Prior to implantation of the valve, TEE is used to assess the entire “landing zone” of the transcatheter heart valve (THV) ( Box 32.1 ). This landing zone may differ depending on the type of valve implanted ( Fig. 32.1 ). The current commercially available balloon-expandable valve (SAPIEN 3) is short in height when fully deployed (15.5–22.5 mm depending on valve size), and the inflow (ventricular) edge is ideally positioned 1–2 mm below the level of the aortic annulus to allow the fabric skirt around the outside of the proximal portion of the valve to seal the annulus and prevent PVR. The current commercially available self-expanding THV (Evolut R) is much longer (∼50 mm), with the outflow end (aortic) within the ascending aorta, and the inflow end ideally positioned 2–5 mm below the annulus. Other valve designs used commercially in Europe are currently in trials in the United States.

Despite higher rates of PVR with the self-expanding valve, clinical outcomes acutely, and at 1 year, do not differ significantly between the two valves. Often, the sizing of the annulus as well as the calcium location and burden, may help to determine the ideal type of THV to implant. However, as more valve types are available, other factors (i.e., bicuspid morphology, preexisting pacemaker, ease of deployment) may also influence the decision-making process.

The most important measurement currently used for THV sizing is the “annulus,” which is a virtual plane at the level of the hinge-point (lowest attachment site) of the three cusps. Because the annulus is often asymmetric and oval with annular diameters largest in the coronal plane and shortest in the sagittal plane, three-dimensional (3D) imaging is required. Although, typically, multislice computed tomography (MSCT) is used for assessing average diameter, the perimeter or area of the annulus may also be used. The 3D TEE has also been validated and may be as accurate as MSCT for these measurements.

It is important to understand the relationship between perimeter sizing and area sizing for TAVR and how this relates to the percent oversizing. The percent oversizing is defined as ((THV nominal measurement/native annular measurement) −1) × 100. For a circular orifice, the percent area oversizing is two times the perimeter oversizing. However, in the setting of an oval annulus, area oversizing will be less than two times the perimeter oversizing. The current balloon-expandable valve uses area oversizing, whereas the current self-expanding valve uses perimeter oversizing. All current devices use systolic measurements, which tend to be the largest measurement during the cardiac cycle, with the lowest risk of undersizing the valve. Advantages of the 3D TEE technique for preprocedural imaging include real-time imaging of the hinge-points of the cusps, and elimination of hand-tracing errors of direct planimetry. Nonetheless, 3D TEE techniques are still limited by ultrasound physics that create blooming and side-lobe artifacts as well as acoustic dropout. In addition, these techniques require expertise and practice. Advances in software packages are currently being developed and should automate many of the steps currently required to obtain 3D-derived measurements, and reduce interobserver variability of echocardiographic measurement of the aortic annulus. Two techniques have been used in the literature: direct planimetry of the short-axis (SAX) plane, and indirect planimetry. The steps for direct planimetry are outlined in Fig. 32.2 . The steps for indirect planimetry are outlined in Fig. 32.3 .

The aortic valve morphology has important implications for procedural success. The extent and distribution of calcium can impact procedural success and has been associated with excessive THV motion during deployment, and PVR. Bulky calcium increases the risk of calcific nodule displacement into the coronary ostia, annular rupture, root perforation, aortic wall hematoma, and aortic dissection ( Fig. 32.4 ). At this time, bicuspid aortic valve morphology is a relative contra-indication to TAVR. However, two reports of TAVR in a series of bicuspid aortic valve patients have shown that, compared to matched trileaflet aortic valve patients, there was no difference in acute procedural success, valve hemodynamics, or short-term survival. Numerous case reports of THV implantations in patients with congenitally abnormal aortic valves have limited the use of TAVR in this population because of reports of significant AR or suboptimal flow characteristics. In the setting of stenosis and limited leaflet motion, a trileaflet valve can be determined by color flow Doppler (CFD) in all three commissures ( Fig. 32.5A and Video 32.1 ) compared to a bicuspid valve with color Doppler in a single long commissure extending to the sinutubular junction (see Fig. 32.5B and Video 32.2 ).

Aortic root morphology is also important in preprocedural planning. The diastolic sinus of Valsalva diameter and height, the diastolic diameter of the sinutubular junction, and the systolic left main coronary artery ostium position may influence the size of THV selected as well as determine valve placement. The location of the coronary ostia is of primary importance since occlusion can lead to catastrophic left ventricular dysfunction. Complications associated with right coronary artery occlusion are significantly less frequent than with left coronary artery occlusion. A meta-analysis of 18 studies showed that coronary obstruction occurred from displacement of the calcified left coronary cusp (and not typically from the stented THV) and the factors associated with coronary obstruction following TAVR include: female sex, small aortic root diameter (mean diameter = 27.8 ± 2.8 mm), and low-lying coronary artery (mean height = 10.3 ± 1.6 mm). Although MSCT is often used for these measurements, 3D TEE imaging compares favorably and allows rapid acquisition of the coronal plane for measurement of the systolic annulus-to-left main distance as well as the length of the left coronary cusp during the procedure ( Fig. 32.6 ).

Wire and Cannulation Position

Occasionally, the position of wires and cannulae must be confirmed. Following any wire placement into the heart, perforation and accumulation of pericardial effusion should be excluded. The right ventricular pacing wire tip is ideally in the right ventricular apex ( Fig. 32.8A and Video 32.5 ). The position of the retrograde stiff wire within the left ventricle (LV) can also easily be assessed by echocardiography (see Fig. 32.8B and Video 32.6 ) with the curve of the J-wire ideally positioned at the apex of the ventricle. The transapical TAVR approach requires additional imaging. Because of the small apical window generated by the limited thoracotomy, imaging of the left ventricular apex from a midesophageal view is useful to ensure optimal location of the apical puncture (see Fig. 32.8C ).

Balloon Aortic Valvuloplasty

Balloon aortic valvuloplasty (BAV) prior to TAVR is used to increase cusp excursion and to ensure adequate cardiac output during THV positioning. Although some studies have suggested preimplant BAV is not required for the implantation of some valve types, other THV types require BAV. A recent study has suggested that BAV prior to implantation of a balloon-expandable valve may reduce cerebral ischemic lesions. BAV can be used diagnostically for both the confirmation of annular sizing, and the prediction of calcium displacement (into the aorta, left main coronary or annular/subannular region) during final THV deployment. Therefore, imaging during and following BAV is important to assess the functional results of the dilatation and possible adverse events.

Ventricular and Baseline Valvular Function

A qualitative assessment of mitral regurgitation (MR), tricuspid regurgitation, and biventricular function should be made prior to implantation. Changes in the severity of MR may indicate mechanical compromise of the mitral apparatus from stiff wires, the THV, left ventricular dysfunction (particularly following pacing), systolic anterior motion following the abrupt reduction in afterload that occurs with valve deployment, increases in blood pressure, or severe aortic regurgitation (AR). An acute reduction in left ventricular or right ventricular function may be a clue to coronary artery compromise during the procedure. Quantitation of right ventricular stroke volume is attempted in order to aid in the final assessment of AR. Deep gastric views of the aortic valve are crucial, allowing accurate Doppler calculation of effective orifice area by continuity equation and assessment of the presence, location, and severity of AR.