Introduction
- Ernesto E. Salcedo, MD
- John D. Carroll, MD
The field of structural heart disease (SHD) has evolved as a group of cardiovascular diseases that are amenable to percutaneous noncoronary interventions. The integration into “heart teams” of multiple specialists including interventionalists, surgeons, and imagers has been the hallmark of SHD programs. , The use of multimodality imaging for the management of patients with SHD has been another hallmark of this field. , Echocardiography, because of its portability, availability, nonionizing nature, low cost, and ability to provide detailed structural and functional information of the cardiovascular system in real time, plays a fundamental role in all phases of SHD interventions.
The term interventional echocardiography in this context refers to the use of echocardiography to assist in cardiac interventions and not to “intervene” with echocardiography. Echocardiography, even with the transesophageal approach, remains at most semiinvasive, without the need to access the intravascular or intracardiac domain. Intravascular ultrasound (IVUS) and intracardiac echocardiography (ICE) , are considered invasive procedures, and they do play a role in the guidance of SHD interventions; however, their use is not discussed here.
In this introductory chapter we present a summary of the use of echocardiography in adults undergoing common SHD interventions. In Table 189.1 , we present key points of the role of echocardiography in patient selection, procedural guidance, and evaluation of results in patients undergoing SHD interventions. The table is organized according to the anatomic structure being intervened, and key references are provided for each intervention. The figures illustrate salient points of imaging with echocardiography during a variety of SHD interventions. We highlight the central role that real-time three-dimensional transesophageal echocardiography (3D TEE) plays in procedure guidance, but also illustrate the value of two-dimensional echocardiography, spectral Doppler, and color Doppler as adjuncts in the image guidance of structural heart disease interventions.
| Patient Selection | Procedural Guidance | Evaluation of Results | |
|---|---|---|---|
| Valvular Interventions | |||
| Transcatheter aortic valve replacement (TAVR) |
|
|
|
| Aortic valve balloon valvuloplasty , |
| Usually done with fluoroscopy |
|
| Edge-to-edge mitral valve repair |
|
|
|
| Mitral valve balloon valvuloplasty , |
|
|
|
| Periprosthetic leak repair |
|
|
|
| Valve-in-valve implantation |
|
|
|
| Atrial Interventions | |||
| Interatrial septum puncture |
|
|
|
| Atrial septal defect closure , |
|
|
|
| Patent foramen ovale closure , |
|
|
|
| LAA occluders |
|
|
|
| LARIAT procedure | Exclusion criteria:
|
|
|
| Ventricular Interventions | |||
| VSD closure , |
|
|
|
| Ventricular pseudoaneurysm closure |
|
|
|
| Alcohol septal ablation , |
|
|
|
Figure 189.1 shows examples of four most common non-valvular interventions, including transcatheter aortic valve replacement (TAVR), percutaneous mitral valve repair using the MitraClip system, mitral valve balloon valvuloplasty, and perivalvular leak repair.
Figure 189.2 shows examples of four most common valvular interventions, including interatrial septal puncture, percutaneous closure of an atrial septal defect (ASD), percutaneous closure of a patent foramen ovale (PFO), and left atrial appendage exclusion procedure.
Figure 189.3 shows examples of the most common ventricular interventions, including closure of a ventricular septal defect (VSD) and alcohol septal ablation (ASA) for hypertrophic obstructive cardiomyopathy.
Transcatheter Aortic Valve Replacement
- Linda D. Gillam, MD, MPH
- Konstantinos Koulogiannis, MD
- Leo Marcoff, MD
- Konstantinos Koulogiannis, MD
Transcatheter aortic valve replacement (TAVR) has emerged as a new option for the treatment of patients with severe symptomatic aortic stenosis (AS) who are inoperable or at greatly increased risk with surgical aortic valve replacement. Echocardiography is an essential tool in patient selection, intraprocedural monitoring, and postprocedure follow-up, with three-dimensional (3D) echocardiography playing an increasingly important role.
Transcatheter heart valve characteristics
Two types of transcatheter heart valves (THVs) are currently available: the balloon-expandable Edwards SAPIEN and SAPIEN-XT valves, and the self-expanding Medtronic CoreValve. Available THV sizes, and the aortic sizes for which they are appropriate, are shown in Tables 190.1 and 190.2 . In Europe, other THVs are commercially available. A description of valve structure, delivery techniques, and clinical experience with these valves is beyond the scope of this chapter, so the reader is referred to the EAE/ASE recommendations for the use of echocardiography in new transcatheter interventions for valvular heart disease for additional detail.
| Valve Size | Aortic Annulus Diameter | Ascending Aorta Diameter | Sinus of Valsalva Diameter | Native Leaflet to Sinotubular Junction Length | Perimeter Measurement (CT) |
|---|---|---|---|---|---|
| CV 23 | 2D TEE: 17-19 mm CT: 18-20 mm | ≤ 34 mm | ≥ 25 mm | ≥ 15 mm | 56.5-62.8 mm |
| CV 26 | 2D TEE: 19-22 mm CT: 20 -23 mm | ≤ 40 mm | ≥ 27 mm | ≥ 15 mm | 62.8-72.3 mm |
| CV 29 | 2D TEE: 22-26 mm CT: 23 -27 mm | ≤ 43 mm | ≥ 29 mm | ≥ 15 mm | 72.3-84.8 mm |
| CV31 | 2D TEE: 25-28 mm CT: 26-29 mm | ≤ 43 mm | ≥ 29 mm | ≥ 15 mm | 81.6-91.1 mm |
| Valve Size | Aortic Annulus Diameter | Distance to Coronaries | Perimeter Measurement (CT) |
|---|---|---|---|
| SAPIEN 23 or SAPIEN XT 23 | 2D TEE: 18-21 mm CT: 19-22 mm | ≥ 10 mm | 60.0-69.0 mm |
| SAPIEN 26 | 2D TEE: 22-24(25) mm CT: 23-25 mm | ≥ 11 mm | 72.0-78.5 mm |
| SAPIEN XT26 | 2D TEE: 22-24 mm CT: 23-25 mm | ≥ 10 mm | 72.0-78.5 mm |
| SAPIEN XT 29 | 2D TEE: 25-27 mm CT: 26-28 mm | ≥ 11 mm | 81.5-88.0 mm |
| SAPIEN XT 29 | 26-29 mm | ≤ 43 mm | 81.6-91.1 mm |
Patient selection
The presence of severe AS must first be established using the current guidelines. Pivotal trials have been limited to patients with high transvalvular velocities and mean gradients (≥ 4 m/sec and ≥ 40 mm Hg, respectively) with allowance for dobutamine stress echocardiography in patients with low-gradient, low ejection-fraction (EF) “severe” AS to differentiate between severe and pseudosevere obstruction. However, subsequent trials and commercial release have extended TAVR to those with low-gradient, low stroke-volume preserved-EF severe AS. Although TAVR has been successfully performed in patients with bicuspid aortic valve, this condition is generally considered a contraindication to TAVR because of the associated aortopathy and the possibly increased risk of asymmetric valve deployment.
Preprocedural imaging
Because currently available THVs come in limited sizes and cannot be recaptured once fully deployed, accurate aortic annular preprocedural sizing is essential (see Tables 190.1 and 190.2 ). Inappropriate sizing may increase the risk of dislodgement and/or severe paravalvular regurgitation. For annular sizing before TAVR, the virtual ring formed by the basal cusp attachment (corresponding to the hinge point of the aortic cusps) is measured, providing the primary determinant of valve size.
Preprocedural echocardiography is typically limited to transthoracic echocardiography (TTE), with transesophageal echocardiography (TEE) restricted to patients in whom TTE annular sizing is ambiguous and/or where preprocedural documentation of the position of the origin of the coronary arteries relative to the annulus has not been obtained with computed tomography (CT).
The aortic annular diameter is measured using the TTE parasternal long-axis view in early systole. Piazza and colleagues reported that this view typically displays the right and noncoronary cusps and tends to underestimate the maximal anteroposterior diameter of the annulus, which is the diameter extending from the hinge point of the right coronary cusp and the base of the commissure between the left and noncoronary cusps. Thus, it is desirable, with two-dimensional (2D) imaging, to angle the transducer to record the largest diameter or use the biplane capability of 3D probes to obtain a view that is aligned with the true anteroposterior diameter of the aortic annulus. Multiplanar reconstruction of 3D volume sets permits the measurement of orthogonal diameters as well as the annular perimeter and area, although this approach may mandate the superior image quality achievable with TEE. The annulus measured by TTE using the conventional long-axis orientation is, in general, 1 mm smaller than that measured by 2D TEE, which is, in turn, 1.5 mm smaller than the corresponding CT measurement; 3D TEE annular measurements, however, more closely approximate those obtained with CT. The recognition that the annulus is frequently noncircular has resulted in increasing emphasis on 3D imaging, which can provide annular perimeters and areas. The preprocedure study may also be used to assess the degree and distribution of calcification, which some studies have reported to be predictors of paravalvular regurgitation. ,
As intraprocedural balloon valvuloplasty and valve deployment carry a risk of coronary occlusion if the distance from the annulus to the ostia is shorter than the length of the coronary cusps, preprocedural measurement of the annulus-to-ostia distances is essential. Although these distances are often measured with CT, they can also be measured with TEE, with 2D adequate for the right coronary but 3D essential to provide the coronal plane views needed to see the left coronary ( Fig. 190.1 ). Because it may be difficult to measure the length of heavily calcified cusps, annulus-ostia distances of greater than 10 and greater than 11 mm are recommended for the 23- and 26-mm balloon-expandable valves, respectively. Although this measurement is not required for the self-expanding valve, other measurements such as the diameter and height of the aortic root and diameter of the ascending aorta are important for this valve (see Tables 190.1 and 190.2 ).
Preprocedural assessment should also include evaluating the degree of upper septal hypertrophy, which can predispose to valve malposition/displacement; assessment of baseline aortic regurgitation (AR), because intraprocedural balloon valvuloplasty can worsen AR; assessing the mitral valve, because it may be damaged during TAVR; and documenting baseline left ventricular function.
Procedural imaging
TEE, ideally with 3D, provides important information during TAVR by confirming preprocedural TTE findings, most importantly annular size. In addition, during predeployment valvuloplasty, TEE can assess balloon position, and the degree to which the expanded balloon fits the annulus can be used as a final THV size check ( Fig. 190.2 /Video 190.2). Most importantly, TEE assesses the severity of postinflation AR, as severe AR may mandate expedited valve deployment.
THV deployment, particularly that of the CoreValve, is guided primarily by fluoroscopy, and it is common to have to withdraw the TEE probe to a degree that limits echocardiographic imaging so as to not interfere with fluoroscopy. However, for the SAPIEN/SAPIEN-XT valves, TEE may assist in positioning the valve, particularly during valve-in-valve procedures in which the THV is deployed inside a dysfunctional bioprosthesis. The recommended final position of the ventricular aspect of the SAPIEN valve is 2 to 4 mm below the annulus. A position that is too high predisposes to paravalvular regurgitation, obstruction of coronary ostia, and device embolization; a position that is too low is associated with paravalvular regurgitation, residual stenosis, mitral regurgitation, conduction abnormality, and increased risk of dislodgement. With echocardiography, it may difficult to detect the interface between the delivery balloon and the superimposed crimped valve, but proper positioning is usually achieved if the percentages of the delivery system (balloon with the crimped valve) and valve above and below the annulus are 40/60 to 50/50 ( Fig. 190.3 /Video 190.3). Note that some degree of operator-independent cranial movement of the valve occurs during deployment, with the aortic end moving on average 3.2 mm and the ventricular end moving 0.75 mm. Coaxiality of the THV relative to the left ventricular outflow tract (LVOT) may also be important, but noncoaxiality may be difficult to correct. For the CoreValve, the desired final position of the lower edge of the stent is 5 to 10 mm below the annulus.
For all THVs, immediate postdeployment imaging is important to confirm valve position; assess valve shape and the degree of asymmetric deployment, if any; establish that cusp motion is unimpeded; and, most important, identify the location and severity of valvular and/or paravalvular regurgitation. 2D TEE, biplane, and 3D imaging using midesophageal and deep transgastric views are all important. Transient mild valvular AR is common but, rarely, an immobile cusp may cause severe valvular AR, typically treated with rapid placement of a second THV (valve-in-valve). Trace to mild paravalvular regurgitation (PVR), often with multiple jets, is also common. More severe degrees of AR are usually treated with postdeployment balloon dilation.
Rare complications identifiable by TEE include valve embolization, aortic root rupture or dissection, coronary ostial occlusion, and mitral valve trauma resulting in significant mitral regurgitation.
As centers gain experience with TAVR, the desire to limit sedation has resulted in a move away from routine intraprocedural TEE to alternative imaging approaches including intracardiac echocardiography or TTE for immediate postdeployment assessment.
Postimplantation follow-up
The postimplantation follow-up of patients with THV is similar to that for surgical prostheses. Key hemodynamic parameters are peak and mean gradients; effective orifice area (EOA), calculated with the continuity equation; and the Doppler velocity index (DVI), defined as the ratio of velocities proximal to and distal to the valve. As is true for all aortic valves, multiple windows including apical, right parasternal, and suprasternal as well as imaging and nonimaging (Pedoff) probes should be employed. The calculation of THV EOA and DVI requires special attention to detail. For the SAPIEN valve, , it has been shown that the LVOT diameter is best measured just proximal to the stent as opposed to inside the stent. Given that there is flow acceleration at both the stent inlet and level of the cusps, it is important that the LVOT sample volume be carefully placed immediately proximal to the stent. Placement of the sample velocity inside the stent will lead to overestimation of both EOA and DVI, and inconsistent LVOT sample sites will result in variable EOAs or DVIs that may incorrectly interpreted as altered valve function. Although it is likely that similar considerations apply to the CoreValve, this has not yet been studied. To date favorable hemodynamics, which appear to be stable over 2 to 3 years, have been demonstrated for both the SAPIEN and CoreValve THVs, with mean gradients typically between 10 and 15 mm Hg and EOAs in the 1.3- to 1.8-cm 2 range.
Accurate assessment of post-TAVR AR may be difficult because of the coexistence of valvular and paravalvular jets and, more importantly, because paravalvular AR (PVR) may consist of multiple jets with highly eccentric trajectories ( Fig. 190.4 /Video 190.4). It is essential that multiple imaging windows (parasternal long and short axes, apical five and three chamber, with nonstandard variations of these views) be employed. Short-axis views should be recorded at multiple levels and are particularly helpful in differentiating valvular from paravalvular jets and identifying multiple paravalvular jets. Quantitation should employ the integrated approach endorsed by the ASE/EAE as well as the Valve Academic Research Consensus 2 (VARC-2) recommendations and should include pressure half-time, assessment of the abdominal and descending thoracic aorta for retrograde flow, and calculation of regurgitant volume and fraction using integrated Doppler (continuity equation) with either RVOT (preferred) or mitral flow as the reference, as well as jet characteristics. As originally recommended in the ASE/EAE guidelines for surgical prosthetic valves and as proposed in the current VARC-2 recommendations, the circumferential extent of PVR) (< 10% = mild, 10% to 29% = moderate, and ≥ 30% = severe) provides another measure of PVR severity. However, this suffers from the limited spatial resolution of color Doppler and is confounded by the origination of PVR at multiple levels, the tendency for jets to splay eccentrically with the result that small adjacent pinhole jets may be misinterpreted as one larger coalesced jet. Thus the short-axis assessment of circumferential extent may be difficult to interpret. Applying the proximal isovelocity surface area (PISA) approach to THVs is difficult when there is less than severe regurgitation. More recently, it has been suggested that direct planimetry of the vena contracta of the regurgitant jet(s) with 3D echocardiography may be helpful. Although this approach is promising, it may be limited because of the spatial and temporal resolution of 3D approaches. Identifying the optimum way of quantitating PVR remains the subject of active investigation because PVR is common (moderate or severe regurgitation present in 10% to 16% of patients at 30 days) and appears to be associated with worse clinical outcomes. , , ,
MitraClip Procedure
- Julia Grapsa, MD, PhD
- Ilias D. Koutsogeorgis, MD
- Petros Nihoyannopoulos, MD
- Ferande Peters, MD
- Bijoy K. Khandheria, MD
- Ilias D. Koutsogeorgis, MD
The MitraClip system is based on the principle of edge-to-edge repair, also known as the Alfieri technique, introduced in 1991 by Italian surgeon Ottavio Alfieri, who successfully treated a patient with anterior leaflet prolapse. , Using a stitch, he approximated the edges of the middle portions of the anterior and posterior leaflets to create a double-orifice mitral valve. The surgical group subsequently reported a series of 260 patients, of whom 80% underwent the Alfieri technique and had additional mitral annuloplasty, which was associated with reduced rate of reoperation within a follow-up period of 5 years.
Studies on effectiveness of mitraclip procedure
The percutaneously implanted MitraClip has been the most studied device for the transcatheter treatment of mitral regurgitation. The Endovascular Valve Edge-to-Edge Repair Study I (EVEREST I) demonstrated efficacy, safety, and clear hemodynamic improvement in patients with moderate-to-severe and severe mitral regurgitation. In the EVEREST II trial, , , the percutaneous approach was safer than surgery (30-day major adverse cardiac events 15% vs. 48%; P < 0.001). Although patients treated with the MitraClip more commonly required surgery to treat residual mitral regurgitation by the first year of follow-up, a limited number of surgeries were needed, and there was no difference in the prevalence of moderate-to-severe and severe mitral regurgitation or mortality at 4 years. Other studies confirmed the efficacy of the MitraClip.
Indications and patient selection
Patient selection criteria for the MitraClip are based on the most recent registries ( Box 191.1 ). Rejection criteria are mitral valve stenosis (valve area < 4 cm 2 ); left ventricular ejection fraction 20% or less and end-systolic diameter greater than 60 mm; or diseases such as Barlow, in which mitral anatomy may not be suitable for the procedure.
Grade 3 or more out of 4 grades
Pathology in A2-P2 area
Coaptation length > 2 mm (depending on leaflet mobility)
Coaptation depth < 11 mm
Flail gap < 10 mm
Flail width < 15 mm
Mitral valve orifice area > 4 cm 2 (depending on leaflet mobility)
Mobile leaflet length > 1 cm
Two-dimensional echocardiography
Preprocedural echocardiography is pivotal for the anatomical assessment of MitraClip suitability. The parasternal short-axis view allows the assessment of the six mitral scallops. A2 and P2 scallops are well viewed with the parasternal long-axis view. In the apical four-chamber view, A3, A2, and P1 scallops (internal to external) are best assessed, whereas P3, A2, and P1 are best assessed in the apical two-chamber view. With the parasternal long-axis view, annular dilatation is identified when the annulus/anterior leaflet ratio is greater than 1.3 (in diastole) or when the annulus diameter is greater than 35 mm.
Assessment of mitral regurgitation with Doppler imaging follows the current guidelines for mitral valve evaluation. , All features of the two-dimensional (2D) assessment of mitral regurgitant severity are summarized in Table 191.1 .
| Parameters | Mild | Moderate | Severe |
|---|---|---|---|
| Q ualitative | |||
| Mitral valve morphology | Normal/abnormal | Normal/abnormal | Flail leaflet/ruptured papillary muscles |
| Color flow mitral jet | Small, central | Intermediate | Very large or eccentric jet |
| Flow convergence zone | None or small | Intermediate | Large |
| Continuous wave Doppler of mitral regurgitation | Faint/parabolic | Dense/parabolic | Dense/triangular |
| Semiquantitative | |||
| Vena contracta width (mm) | < 3 | Intermediate | ≥ 7 (> 8 for biplane) |
| Pulmonary vein flow | Systolic dominance | Systolic blunting | Systolic flow reversal |
| Mitral inflow | A wave dominant | Variable | E wave dominant (> 1.5 m/sec) |
| Mitral to aortic time-velocity integral ratio | < 1 | Intermediate | > 1.4 |
| Quantitative | |||
| Effective regurgitant orifice area (mm 2 ) | < 20 | 20-39 | ≥ 40 |
| Regurgitant volume (mL) | < 30 | 30-59 | ≥ 60 |
Transesophageal echocardiography
Multiplane transesophageal echocardiography (TEE) is the gold standard modality for preoperative assessment as well as intraprocedural guidance for MitraClip insertion. To perform a comprehensive examination of the mitral valve, it is essential to understand how transesophageal probe maneuvers change the imaging plane with respect to the mitral valve. The typical TEE examination begins with an assessment of the valve in three horizontal planes ( Table 191.2 ).
| View | Comments |
|---|---|
| Mid-esophageal Four-chamber 0-20 degrees | Assessment of mitral valve Particular attention to the mitral annulus, leaflet morphology, leaflet motion, and subvalvar apparatus |
| Mid-esophageal Four-chamber 0-20 degrees | Assessment of mitral valve: A1/P1 Flexion or withdrawal of the probe slightly will bring A1/P1 into view; the anterolateral commissure can be assessed |
| Mid-esophageal Bicommissural 60-70 degrees | Commissure-to-commissure annulus dimension (end-diastole and end-systole) |
| Mid-esophageal Posteromedial commissure 90 degrees | Assessment of mitral valve: A3/P3 The posteromedial commissure can be seen by turning the probe toward the aorta and then coming back to the mitral valve |
| Mid-esophageal Long-axis 120-150 degrees | Assessment of mitral valve: A2/P2 Anterior-to-posterior annulus dimension (end-diastole and end-systole) |
In the standard mid-esophageal four-chamber view (typically at a transducer angle of 0 degrees), A1 and P1 scallops are best visualized. From this position, flexion and withdrawal of the transducer tip allow visualization of the aortic root and anterolateral portions of the mitral leaflets, 120 degrees (A2 and P2) ( Figs. 191.1 and 191.2 ). Similarly, retroflexion and advancement of the transducer tip allow visualization of the posteromedial portions of the leaflets (A3 and P3).
The mid-esophageal plane at an angle between 45 and 90 degrees provides the opportunity for mitral leaflets to be examined with a plane parallel to the mitral orifice and to confirm mitral valve pathology. Through the major axis of the valve orifice, P1, A2, and P3 may be evaluated. Subsequently, by manual rotation of the probe in a clockwise direction, the entire anterior leaflet can be visualized (A1, A2, and A3). Counterclockwise probe rotation provides visualization of the entire posterior leaflet (P1, P2, and P3).
Other imaging planes and transducer positions, such as the transgastric short-axis view, may be used for additional imaging and to assist with the assessment of the mitral valve. ,
Three-dimensional transesophageal echocardiography
Assessment of mitral valve anatomy by real-time three-dimensional (3D) TEE has proved to be superior compared to 2D TEE. The standard techniques of real-time 3D TEE have recently been described. The surgeon’s view, with the aortic root at 12 o’clock, is important for assessment of the preoperative mitral valve ( Fig. 191.3 ) and proximal isovolumic surface area ( Fig. 191.4 ). Based on acquired 3D images, postprocessing software products (TomTec Imaging Systems, Unterschleissheim, Germany) may be used to reconstruct the mitral valve annulus and coronary sinus. Note the 3D volume-rendered reconstruction of the coronary sinus around the mitral valve annulus.
Essentially, the 3D dataset can be rotated to the best view on the orifice of the coronary sinus in real time, thus aiding the interventionalist to adapt the position of the catheter under TEE guidance. To document the success of the annuloplasty procedure, the rendered 3D image can be used to exactly quantify measurements of the mitral valve and mitral valve annulus using dedicated software (QLAB 7.0, Philips Healthcare, Amsterdam). With this technique, the mitral valve and its annulus can be characterized with regard to the perimeter, width of the annulus, and anterior-to-posterior and anterolateral-to-posteromedial diameter. Several studies , have employed the usefulness of 3D TEE in mitral valve interventions with the aim of detecting the gold standard index for assessment of different jets. Direct measurement of multiple vena contracta areas using 3D TEE allows for assessment of mitral regurgitation severity in patients with multiple jets, particularly for mitral regurgitation degrees greater than mild and in cases of more than two jets, for which geometric assumptions may be challenging. ,
Mitraclip procedure guidance
The MitraClip procedure is divided into seven important steps (Videos 191.1 and 191.2). ,
Transseptal Puncture
Transseptal puncture represents one of the most important aspects of the MitraClip procedure. The optimal puncture site is located superiorly and posteriorly in the interatrial septum. The most important TEE planes to identify the correct site are the short-axis view at the base for anterior-posterior orientation (∼ 30 degrees), bicaval view for superior-inferior orientation (∼ 90 to 120 degrees), and four-chamber view (∼ 0 degrees) to direct the height above the mitral valve. Because it combines the short-axis view with the long-axis view, 3D x-plane is important for the determination of the correct puncture site. The position of the MitraClip needle can be seen as tenting of the interatrial septum. The tip of the tenting points towards the left atrium. The site of optimal transseptal puncture may differ. In fibroelastic disease, the puncture site needs to be 4 to 5 cm above the mitral annulus to secure adequate space for a catheter and MitraClip maneuvering. On the other hand, in functional mitral regurgitation, the puncture site needs to be more inferior and closer to the annular plane because of extensive tethering and because the line of coaptation is below the plane of the mitral annulus. A patent foramen ovale should be avoided, as this entry is too far anterior. An atrial septal defect also is not suitable for the MitraClip procedure, as the defect is larger than the sheath size and there is risk of interatrial rupture.
Steerable Guide Catheter Introduction into the Left Atrium
A steerable guide catheter with dilator is advanced into the left atrium over a wire and placed in the left upper pulmonary vein under fluoroscopic and TEE guidance. The dilator has a cone-shaped tip and, therefore, may be easily identified, as it has an echogenic appearance with TEE. A radiopaque echo-bright double ring characterizes the tip of the guide catheter. The advancement of the catheter should be followed constantly with TEE as well and fluoroscopic monitoring to avoid left atrial free wall damage. Once the catheter is placed in the left atrium, the dilator is retrieved first, followed by the wire.
Advancement of the Clip Delivery System into the Left Atrium
The clip delivery system is advanced via the catheter under fluoroscopic guidance. Transesophageal echocardiography and 3D TEE are necessary to ensure that the tip of the catheter remains across the interatrial septum and that the clip delivery system will not cause damage to the left atrial free wall. It is important always to monitor the distance of the clip delivery system from the atrial wall with 3D TEE.
Steering and Positioning of the MitraClip above the Mitral Valve
The posterior withdrawal of the catheter and retraction of the whole system will help the correct positioning of the clip delivery system above the mitral valve medial segment. Again, 3D TEE is important for the monitoring of the steps. The mid-esophageal intercommissural view and the rotation of the system in the anterior and posterior direction are important for the adjustment of the MitraClip.
To ensure correct MitraClip alignment, both arms of the device should be visualized in full length in the long-axis view, whereas no device arms should be seen in the intercommissural view. The MitraClip should split the regurgitation jet in both orthogonal views, and the tip of the device should be directed toward the largest proximal isovelocity surface area. If imaging is difficult, the transgastric view may be important to determine orientation of the device. Overall, avoid the transgastric view if 3D TEE is available. A single 3D en face view allows visualization of correct alignment and proper orientation perpendicular to the line of mitral valve coaptation.
Advancement of the MitraClip into the Left Ventricle
Advancement of the MitraClip into the left ventricle may be monitored with x-plane imaging using the intercommissural and mid-esophageal long-axis views simultaneously. Under fluoroscopic and TEE guidance, crossing of the mitral valve is monitored. The orientation of the device and delivery system must be monitored from the left ventricle because the device may rotate during its transition from the left atrium to the ventricle. The most important views are the intercommissural and long axis. The transgastric view allows visualization of the device alignment relative to the line of coaptation. To visualize the MitraClip in relation to the mitral valve and the line of coaptation, 3D TEE from either the left atrium or left ventricle present direct views. It is easiest to maintain a left atrial 3D mitral view, which may be used if the device orientation cannot be judged adequately. Intercommissural and long-axis views are useful to verify that the device is splitting the mitral regurgitant jet and both mitral leaflets are freely moving above the device arms.
Grasping of the Leaflets and Assessment of Proper Leaflet Insertion
After correct positioning of the MitraClip, grasping of the leaflets between the device arms is monitored using a mid-esophageal long-axis view ( Fig. 191.5 ). It is always important to acquire a longer loop during the grasping of the leaflets. Furthermore, it is recommended to initially close the MitraClip only up to 60 to 90 degrees in angulation and subsequently fully close the device after determination of proper leaflet insertion and demonstration of regurgitation reduction. Insertion of the posterior leaflet is commonly best seen in the long-axis view, and the insertion of the anterior leaflet in the four-chamber view. The intercommissural view will have an additive role. Once the leaflets are well positioned between the device arms and there is clear reduction of mitral regurgitation, the MitraClip can be closed.
Assessment of Result and MitraClip Release
After positioning the MitraClip, it is important to evaluate the structural difference of the mitral valve ( Fig. 191.6 and Videos 191.3 and 191.4). Initial evaluation of the MitraClip result is usually performed under general anesthesia. It is important to perform repeat assessment of the regurgitation after the patient recovers from general anesthesia and under hemodynamic conditions similar to those for the preoperative assessment. Furthermore, ultrasound machine settings should be the same. Evaluation of the grade of residual mitral regurgitation may lead to further adjustment after a MitraClip implantation or the addition of another device. It is important to understand that the area of color jets will be larger with multiple jets, which commonly occurs because of the addition of multiple jet areas after a MitraClip is implanted, than if there is a single jet. This may potentially lead to overestimating residual regurgitation in patients with multiple jets. , , In addition, the artifact caused by the MitraClip using 2D echocardiography also may influence imaging. New studies , will discover the gold standard imaging index for best assessment after MitraClip insertion.
Additional MitraClip Implantation
When a second MitraClip is required, the orientation of the second device should be optimized by 2D or, when available, 3D echocardiography in the left atrium. Fluoroscopy has greater value in the guidance of inserting the additional device, which should always be aligned as parallel as possible to the first device. Folding of leaflet tissue between two MitraClips should be avoided as this may cause significant residual mitral regurgitation. ,
Acknowledgments
The authors gratefully acknowledge Joe Grundle and Katie Klein for their editorial assistance and Brian Miller and Brian Schurrer for their help with the figures.
Mitral Balloon Valvuloplasty
- Michael S. Kim, MD
- Ernesto E. Salcedo, MD
In contemporary times, patients with mitral stenosis (MS) typically present during adulthood. Childhood rheumatic valvulitis (which occurs in approximately two thirds of all cases of rheumatic fever) remains the most common etiology of MS and results in fibrosis and scarring of the mitral valve leaflets and fusion of the leaflet commissures. The incidence of rheumatic MS remains high in both developing countries and the South Pacific. Although the widespread use of antibiotics used to treat streptococcal infections has led to a reduced incidence of this syndrome in Western countries, changing immigration patterns to the United States and other industrialized countries coupled with new strains of streptococci associated with rheumatic fever has brought with it a resurgence of patients suffering from rheumatic MS in developed countries. ,
Until the mid-1980s, mitral valve surgery (i.e., closed commissurotomy, mitral valve replacement) was the only reliable therapy for patients suffering from mitral stenosis. The introduction of the Inoue balloon catheter in 1984 (with subsequent U.S. Food and Drug Administration approval of the balloon catheter in 1994), however, led to a radical shift in the invasive treatment of rheumatic mitral stenosis such that percutaneous balloon mitral commissurotomy (BMC) became a well-accepted, safe, and cost-effective means by which to provide symptomatic and hemodynamic relief to patients suffering from severe rheumatic MS. The advent of advanced imaging with three-dimensional (3D) echocardiography has further revolutionized BMC and now plays an integral role in clinical diagnosis and determining the feasibility of BMC as well as procedural guidance and immediate evaluation of technical results. , This chapter reviews percutaneous balloon mitral commissurotomy as it is practiced today and specifically highlights the pre-, intra-, and postprocedural utility of advanced echocardiography.
Etiology of mitral stenosis
The pathologic entity of “mitral stenosis” has become synonymous with “rheumatic mitral stenosis” (more than 90% of all cases of severe MS are rheumatic in etiology). The hallmark of rheumatic mitral stenosis is one of fusion of the mitral leaflet commissures, typically in association with subvalvular thickening and/or multivalvular involvement. It is important to note, however, that there are other (less common) pathologic etiologies of MS, including congenital mitral stenosis, carcinoid, and eosinophilic endomyocardial fibroelastosis. In contrast, given the aging population and increased prevalence of disease states predisposing patients to calcific lesions (e.g., chronic hemodialysis), calcific mitral stenosis in association with severe mitral annular calcification (MAC) is becoming an increasingly common etiology of severe MS. In contrast to rheumatic MS, in calcific MS it is common for annular calcification to extend toward and involve the body of the leaflets, thereby restricting overall leaflet motion. Thus, in calcific MS, there may be little to no involvement of either the leaflet tips or chordae in the underlying pathophysiologic state, and commissural fusion may either be entirely absent or, if present, be due to dense calcification in the commissures themselves ( Fig. 192.1 ).
Patient selection for balloon mitral commissurotomy
Balloon mitral commissurotomy has become the therapy of choice for most patients with symptomatic mitral stenosis ( Table 192.1 ) and is recommended in symptomatic patients with a mitral valve area less than 1.5 cm 2 , favorable valve morphology (see later discussion), and absence of both left atrial thrombus and severe mitral regurgitation. BMC is also recommended in asymptomatic patients with moderate to severe MS and favorable valve morphology who demonstrate severe pulmonary hypertension either at rest (pulmonary artery systolic pressure [PASP] > 55 mm Hg) or provoked with exercise (PASP > 60 mm Hg).
| Class I | 1. BMC is indicated for the following patients with moderate or severe MS and valve morphology favorable for BMC in the absence of LAA thrombus or moderate to severe MR: A. Symptomatic patients (NYHA functional class ≥ II) B. Asymptomatic patients with pulmonary hypertension (PASP > 50 mm Hg at rest or > 60 mm Hg with exercise) |
| Class IIa | 1. BMC is reasonable for patients with moderate or severe MS who have a nonpliable calcified valve, are in NYHA functional class ≥ III, and are either not candidates or at high risk for surgical MVR |
| Class IIb | BMC may be considered for the following patients in the absence of LAA thrombus or moderate to severe MR: A. Asymptomatic patients with moderate or severe MS and valve morphology favorable for BMC who have new onset atrial fibrillation B. Symptomatic patients (NYHA functional class ≥ II) with MVA greater than 1.5 cm 2 if there is evidence of hemodynamically significant MS based on PASP > 60 mm Hg, PCWP > 25 mm Hg, or mean mitral valve gradient > 15 mm Hg during exercise C. Patients with moderate or severe MS who have a nonpliable calcified valve and are in NYHA functional class ≥ III, as an alternative to surgery |
| Class III | 1. BMC is not indicated for patients with mild MS 2. BMC should not be performed in patients with moderate to severe MR or LAA thrombus |
Suitability of valve morphology for BMC is typically assessed by determination of the echocardiographic Wilkins score ( Table 192.2 ), the most widely adopted prognostic score determining a favorable BMC outcome. The Wilkins score is derived from noninvasive echocardiographic data focusing on four variables: valve leaflet mobility, thickening, calcification, and degree of subvalvular thickening. A value of 1 to 4 is assigned to each variable, with higher scores indicative of more extensive disease. In general, a calculated Wilkins score of 8 or less in the absence of severe mitral regurgitation has been shown to portend a favorable result from BMV, whereas scores above 8 have an increased risk of adverse outcomes and should strongly be considered for alternative (e.g., surgical) therapy. However, in centers experienced in the performance of BMC, even in many unfavorable candidates, BMC is still considered a first-line therapeutic choice for rheumatic MS after thoughtful preprocedural consultation and open discussion with the patient and family about treatment options and goals. Although the eventual need for valve replacement therapy is a reality for most patients, minimizing symptoms while maximizing the life of a patient’s native mitral valve remain paramount objectives in the management of patients with severe MS.
| Grade | Mobility | Subvalvular Thickening | Thickening | Calcification |
|---|---|---|---|---|
| 1 | Highly mobile valve with only leaflet tip restriction | Minimal thickening just below the leaflets | Leaflets near normal thickness (4-5 mm) | Single area of calcification |
| 2 | Normal mobility of mid and base leaflet segments | Thickening of chordal structures extending up to 1/3 of chordal length | Mid-leaflets normal; moderate to severe thickening (5-8 mm) of leaflet margins | Scattered areas of calcification confined to leaflet margins |
| 3 | Valve moves forward in diastole, mainly from the base | Thickening extends to distal 1/3 of chords | Moderate to severe thickening (5-8 mm) of the entire leaflet | Calcification extends to mid-leaflets |
| 4 | No or minimal forward movement during diastole | Extensive thickening and shortening of all chordal structures extending to papillary muscles | Severe thickening (> 8-10 mm) of the entire leaflet | Extensive calcification throughout leaflets |
Role of three-dimensional transesophageal echocardiography in balloon mitral commissurotomy
Structural heart disease interventions are performed in a complex and dynamic 3D environment necessitating the real-time (RT) incorporation of multiple imaging modalities to both guide procedures and assess outcomes. Compared with traditional two-dimensional (2D) echocardiography, RT 3D transesophageal echocardiography (TEE) provides a wide field of view with superior depth resolution, allowing for enhanced simultaneous imaging of soft tissue interventional targets (e.g., valves), related spatial anatomy, and interventional devices ( Fig. 192.2 ). In so doing, RT 3D TEE has the potential to increase the safety of the BMC procedure by providing enhanced navigation of particular procedural steps (e.g., transseptal puncture) and reducing overall radiation from fluoroscopy. In addition, 3D TEE has been shown to be an effective technique to monitor the efficacy of BMC, specifically with regard to providing detailed visualization of commissural splitting and leaflet tears that were previously difficult to appreciate on traditional 2D echocardiography. ,
Technique for balloon mitral commissurotomy
Although BMC may be performed by several techniques (antegrade vs. retrograde approach, single vs. double balloon technique, etc.), the most common and extensively studied approach has been an antegrade approach with the Inoue balloon catheter. , The Inoue balloon is a self-positioning and pressure-extensible balloon composed of nylon and rubber micromesh. The balloon is composed of three sections with distinct elastic properties, thereby allowing for sequential inflation ( Fig. 192.3 ). Sequential inflation allows fast and stable balloon inflation across the stenotic valve with no need for physiologic cardiac standstill (e.g., through rapid ventricular pacing). In addition, the balloon is designed to be temporary slenderized, allowing for a lower profile entry into the femoral vein and left atrium. Although the technical details of the BMC procedure are beyond the scope of this chapter, the general steps are as follows. During cardiac catheterization, a transseptal puncture is used to gain access to the left atrium. Following serial dilation of the interatrial septum, the slenderized Inoue catheter is advanced into the left atrium. The balloon is then unslenderized in sequential fashion and then advanced across the stenotic mitral valve using a steering wire. The balloon is then rapidly inflated and deflated in sequential fashion across the stenotic valve, resulting in separation of the fused commissures ( Fig. 192.4 ). At this point in the procedure, both invasive hemodynamics and echocardiography (especially 3D echocardiography) are used to determine the physiologic and anatomic impact of balloon inflation (decreased left atrial pressure and transmitral gradient, increased cardiac output, confirmation of commissural splitting, degree of mitral regurgitation) and the need and/or safety of proceeding with subsequent balloon inflations. Once an adequate hemodynamic and anatomic result has been achieved, the balloon is reslenderized and removed from the body.
