Isolated reoperative tricuspid valve replacement is one of the highest risk operations classified in the Society of Thoracic Surgeons registry, particularly in the setting of preexisting right ventricular dysfunction. Transcatheter tricuspid valve-in-valve implantation represents an attractive alternative to redo surgery in patients with tricuspid bioprosthetic valve degeneration who are considered high-risk or unsuitable surgical candidates. In this review article, the authors discuss the emergence of transcatheter tricuspid valve-in-valve therapy, preprocedural echocardiographic assessment of tricuspid bioprosthetic valve dysfunction, periprocedural imaging required for tricuspid valve-in-valve implantation, and postprocedural assessment of tricuspid transcatheter device function.
Highlights
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This review article describes the emergence of transcatheter tricuspid valve-in-valve procedures for a failing tricuspid bioprosthesis.
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Preprocedural assessment of degenerative tricuspid valve bioprostheses using transthoracic echocardiography is described.
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A step-by-step guide to the transesophageal images required for successful transcatheter tricuspid valve-in-valve implantation is described.
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The article concludes with a comprehensive review of postprocedural transthoracic follow-up imaging.
Transcatheter valve-in-valve (ViV) procedures are attractive alternatives to redo conventional surgery to treat dysfunctional aortic and mitral bioprostheses. Until recently, transcatheter tricuspid valve (TV) implantation within either an existing surgical bioprosthesis (tricuspid ViV implantation) or a previously repaired TV had been limited to small case series or case reports. However, with the recent publication of the global transcatheter tricuspid Valve-in-Valve International Database (VIVID) registry, and recognition that redo surgery for failing TV bioprosthesis carries increased morbidity and mortality, particularly when preexisting right ventricular (RV) dysfunction is present, it is likely that tricuspid ViV procedures will become an increasingly recognized alternative to redo surgical TV intervention. Moreover, novel transcatheter techniques to repair native regurgitant TVs are also emerging. Facilitation of successful transcatheter TV procedures requires comprehensive understanding of two-dimensional (2D) and real-time (RT) three-dimensional (3D) transthoracic echocardiographic and transesophageal echocardiographic (TEE) images of the normal and diseased TV, to permit early and accurate detection of TV disease, to direct the timing and assess the effectiveness of treatment, to guide transcatheter TV interventions, and to assess residual TV disease.
Anatomic Considerations and Implications for TV Surgery
The TV apparatus is composed of three leaflets (anterior, posterior, and septal) attached to the myocardium of the right ventricle either directly or by the means of chordae linked to a papillary muscle. Autopsy studies, however, report highly variable anatomy; in one study, the TV was found to be a single leaflet in 17% of cases, bicuspid in 72%, and tricuspid in only 17%, with the posterior leaflet being frequently either absent or incorporated into the anterior or septal leaflets. Other studies report absent septal papillary muscle or presence of accessory leaflets in a high proportion of human hearts. In tricuspid regurgitation (TR), anatomic distortion may be accentuated by multiple chordal attachments between the myocardium and valve leaflets, resulting in secondary leaflet tethering with RV dilatation. This process is aggravated by volume overload, which results not only in TV distortion but progressive deterioration in RV systolic function. As a result, severe TV disease has been associated with a threefold increase in all-cause mortality rate and a four- to fivefold increased incidence of cardiac events during long-term follow-up, while elective tricuspid annuloplasty for patients with functional TR undergoing elective left-sided heart surgery is associated with a reduction in cardiac-related mortality and improved echocardiographic outcomes.
Because of the anatomic complexity of the TV and coexisting advanced RV disease, almost 30% of patients are deemed unsuitable for surgical TV repair at presentation and are instead offered TV replacement. Although robust comparative data are unavailable, implantation of a bioprosthesis is preferred in current practice. In addition, the increased bleeding risk associated with long-term oral anticoagulation and mechanical valve replacement can be avoided. A recently published meta-analysis of observational studies showed no differences between mechanical and biologic TV replacement in terms of survival and reoperation. However, the risk for valve thrombosis was significantly higher in patients with mechanical prostheses. For reasons still unclear, the longevity of tricuspid bioprostheses seems shorter compared with that of bioprostheses exposed to the systemic circulation (aortic, mitral). This translates into a reoperation rate of about 20% for valve degeneration within 10 years and freedom from reintervention of only 53% at 15 years after surgical valve replacement.
Emergence of Transcatheter Treatment Alternatives
Reoperation for valve degeneration is associated with mortality ranging from 17% to 37%, and isolated reoperative TV replacement is one of the highest risk operations classified in the Society of Thoracic Surgeons registry. Novel transcatheter therapies are emerging for the treatment of TR, including transcatheter tricuspid ViV implantation for patients with tricuspid bioprosthetic valve stenosis and/or transvalvular regurgitation deemed too high risk or unsuitable for reoperation. Notwithstanding, younger patients with Ebstein’s anomaly requiring multiple valve replacements because of somatic growth or bioprosthesis degeneration may also benefit from transcatheter intervention as a mechanism to extend the duration between repeat valve operations.
Tricuspid ViV transcatheter treatment of degenerated tricuspid bioprostheses was first successfully performed using the Melody valve (Medtronic, Minneapolis, MN) in 2010 through a jugular venous route in a patient with previous TV replacement (27-mm Medtronic Mosaic valve) 8 years after treatment for TV endocarditis. Evolution of the access routes subsequently followed: in 2010, a 26-mm Edwards SAPIEN transcatheter heart valve (Edwards Lifesciences, Irvine, CA) was implanted for the first time into a Medtronic Mosaic 27-mm bioprosthesis through a right atriotomy (off pump), and a fully percutaneous procedure using the jugular venous approach was described shortly later using a 23-mm SAPIEN valve in 2011. Upon commercial availability of the steerable RetroFlex delivery system, transfemoral venous implantation of a SAPIEN XT valve became technically possible, paving the way for a simplified and more convenient tricuspid ViV procedure. Subsequently, the safety, feasibility, and efficacy of the tricuspid bioprosthesis ViV procedure has been confirmed in multiple case reports and series. The largest series published to date, the tricuspid VIVID registry, reported on the outcomes of 152 patients. In this cohort, the age of the failing surgical bioprostheses was ≤5 years in as many as 30% of the patients, highlighting the accelerated degeneration observed in tricuspid bioprostheses. Overall, the study confirmed high procedural success (99%) as well as excellent safety, with only one procedural death and no acute conversion to open-heart surgery despite two valve embolizations that were managed percutaneously. Significant improvement of invasive transvalvular gradient and severity of TR were observed regardless of the type of valve implanted, which translated into sustained functional improvement in 76% of patients. Survival free from reintervention was 85% at 1 year. Valve thrombosis was suspected in 4 patients (3%), and 4 additional patients (3%) met the criteria for valve endocarditis. All-cause mortality was low, with a reported incidence of 3% at 30 days and a total of 22 deaths (15%) during a median follow-up period of 13 months.
Emergence of Transcatheter Treatment Alternatives
Reoperation for valve degeneration is associated with mortality ranging from 17% to 37%, and isolated reoperative TV replacement is one of the highest risk operations classified in the Society of Thoracic Surgeons registry. Novel transcatheter therapies are emerging for the treatment of TR, including transcatheter tricuspid ViV implantation for patients with tricuspid bioprosthetic valve stenosis and/or transvalvular regurgitation deemed too high risk or unsuitable for reoperation. Notwithstanding, younger patients with Ebstein’s anomaly requiring multiple valve replacements because of somatic growth or bioprosthesis degeneration may also benefit from transcatheter intervention as a mechanism to extend the duration between repeat valve operations.
Tricuspid ViV transcatheter treatment of degenerated tricuspid bioprostheses was first successfully performed using the Melody valve (Medtronic, Minneapolis, MN) in 2010 through a jugular venous route in a patient with previous TV replacement (27-mm Medtronic Mosaic valve) 8 years after treatment for TV endocarditis. Evolution of the access routes subsequently followed: in 2010, a 26-mm Edwards SAPIEN transcatheter heart valve (Edwards Lifesciences, Irvine, CA) was implanted for the first time into a Medtronic Mosaic 27-mm bioprosthesis through a right atriotomy (off pump), and a fully percutaneous procedure using the jugular venous approach was described shortly later using a 23-mm SAPIEN valve in 2011. Upon commercial availability of the steerable RetroFlex delivery system, transfemoral venous implantation of a SAPIEN XT valve became technically possible, paving the way for a simplified and more convenient tricuspid ViV procedure. Subsequently, the safety, feasibility, and efficacy of the tricuspid bioprosthesis ViV procedure has been confirmed in multiple case reports and series. The largest series published to date, the tricuspid VIVID registry, reported on the outcomes of 152 patients. In this cohort, the age of the failing surgical bioprostheses was ≤5 years in as many as 30% of the patients, highlighting the accelerated degeneration observed in tricuspid bioprostheses. Overall, the study confirmed high procedural success (99%) as well as excellent safety, with only one procedural death and no acute conversion to open-heart surgery despite two valve embolizations that were managed percutaneously. Significant improvement of invasive transvalvular gradient and severity of TR were observed regardless of the type of valve implanted, which translated into sustained functional improvement in 76% of patients. Survival free from reintervention was 85% at 1 year. Valve thrombosis was suspected in 4 patients (3%), and 4 additional patients (3%) met the criteria for valve endocarditis. All-cause mortality was low, with a reported incidence of 3% at 30 days and a total of 22 deaths (15%) during a median follow-up period of 13 months.
Transthoracic Echocardiographic Assessment of Degenerative TV Bioprosthesis
Preprocedural transthoracic echocardiography (TTE) is an excellent first-line diagnostic tool in the assessment of tricuspid bioprosthetic valve function, as the anterior location of the TV permits favorable echocardiographic visualization and evaluation of prosthetic valve function. The primary goal of TTE is to evaluate the severity, mechanism, and anatomic substrate for prosthetic valve dysfunction, which may involve tricuspid stenosis (TS), TR, or a combination of TS and TR. Common causes of tricuspid bioprosthetic valve dysfunction include leaflet degeneration, leaflet thrombosis, endocarditis-related leaflet damage, and pannus formation. Paravalvular regurgitation is usually related to endocarditis or surgical suture tear. TTE should determine the presence or absence of thrombus, infective endocarditis, or paravalvular leak, as these are exclusion criteria for transcatheter tricuspid ViV. The specific role of TTE in determining the size of surgical and transcatheter valve devices is limited; operative notes, multislice computed tomography (MSCT), TEE imaging, and fluoroscopy are more reliable modalities for selecting transcatheter device size (see below).
Comprehensive assessment of a patient with tricuspid bioprosthesis degeneration should include 2D and 3D imaging, as well as color flow, continuous-wave (CW), and pulsed-wave Doppler imaging. Multiple windows should be used: parasternal RV inflow and short-axis, apical four-chamber, and subcostal views. On the occasion that acoustic shadowing limits evaluation in conventional views, alternative transthoracic echocardiographic windows such as short-axis subcostal or low parasternal may prove as useful as TEE imaging. In patients with adequate 2D images, simultaneous biplane imaging in orthogonal planes with complementary 3D images allows comprehensive evaluation of the prosthetic TV and its leaflets. However, low temporal and spatial resolutions are recognized limitations of 3D TTE of the TV. As with all prosthetic valves, the valve size of the tricuspid bioprosthesis should be recorded, if known, in all cases.
Tricuspid Bioprosthetic Valve Stenosis
A combination of quantitative and qualitative assessments is used to determine the presence and severity of prosthetic TS ( Table 1 , Figure 1 ). Two-dimensional imaging of the TV bioprosthesis includes evaluation of valve seating, leaflet appearance, and leaflet mobility. The appearance of leaflet thickening, calcification, and/or hypomobility ( Video 1 , available at www.onlinejase.com ), with right atrial enlargement and a dilated noncollapsing inferior vena cava (IVC; Video 2 , available at www.onlinejase.com ), may suggest the presence of TV stenosis. Normal color flow Doppler signal across the tricuspid bioprosthesis is typically laminar in appearance; turbulent and/or narrowed or eccentric color Doppler inflow suggests the presence of prosthetic TV stenosis ( Video 3 , available at www.onlinejase.com ). CW Doppler across the prosthetic valve inflow measures transvalvular peak velocity and mean gradient and has been validated against catheter-derived data. To capture maximal transvalvular gradients, CW Doppler interrogation of prosthetic valve inflow should be performed from multiple echocardiographic windows, although the typical window to obtain the highest Doppler velocity is the apical four-chamber view, in which the flow direction is parallel to the transducer beam. The baseline should be shifted and the scale adjusted accordingly to allow optimal visualization and tracing of the spectral Doppler signal. CW Doppler measurements may vary with both heart rate and respiration, and a minimum of five cardiac cycles should be recorded and averaged to account for respirophasic variation of right-sided flow, even when the patient is in sinus rhythm. The average heart rate should also be noted because it can substantially affect the inflow gradient: diastole (time for atrial emptying) shortens with increasing heart rate, and a shorter diastole will of necessity result in a higher mean gradient.
| Consider TV stenosis ∗ | |
|---|---|
| Peak velocity † | >1.7 m/sec |
| Mean gradient † | ≥6 mm Hg |
| PHT | ≥230 msec |
| EOA and VTI PrTV /VTI LVOT | ‡ |
∗ Average more than five cycles to account for respiratory variation.
† May also be increased with valvular regurgitation. Reprinted from Zoghbi et al .
‡ Although the current guidelines for the echocardiographic assessment of TV prostheses do not include cutoffs for EOA and VTI PrTV /VTI LVOT , Blauwet et al . published data on a large series ( N = 285) of a number of TV prosthesis models and sizes that include proposed cutoffs for these hemodynamic variables.
Doppler parameters such as peak E velocity, peak A velocity (in sinus rhythm), and velocity-time integral (VTI) across the valve can be measured to corroborate qualitative findings. Measurement of pressure half-time (PHT) and calculation of prosthetic valve effective orifice area (EOA) are additional parameters that can quantify prosthetic TV stenosis. The PHT is the time required for the maximal pressure gradient to decrease by half. Transvalvular gradient may be increased because of obstruction or regurgitation. In the context of increased transvalvular mean gradient, the PHT is a useful tool to differentiate between the two, as a prolonged PHT is suggestive of obstruction. Note that the PHT should not be used to calculate the EOA of TV prostheses but rather serve as a stand-alone measurement, because PHT-derived EOA calculation overestimates TV area compared with continuity equation–derived methods. The continuity equation is the preferred method for calculation of prosthetic TV valve EOA. This is typically performed by calculating the stroke volume across the left ventricular outflow tract (LVOT) and dividing it by the CW Doppler–derived prosthetic TV VTI. This calculation is accurate in the absence of significant aortic or TR. In the context of greater than mild aortic regurgitation (and if pulmonic valve regurgitation is no more than mild), the RV outflow tract stroke volume may be used instead of LVOT stroke volume. If greater than mild TR is present, the continuity equation should not be used to assess EOA. According to American Society of Echocardiography guidelines, peak TV velocity > 1.7 m/sec, mean gradient > 6 mm Hg, and/or PHT > 230 msec suggest prosthetic TV obstruction ( Table 1 ). In a large, more recent series of normal TV bioprostheses evaluated early after implantation, alternative thresholds for abnormal Doppler flow parameters have been proposed: transvalvular peak velocity > 2.1 m/sec, mean gradient > 8.8 mm Hg, and PHT > 193 msec.
Tricuspid Bioprosthetic Valve Regurgitation
As with TS, a combination of quantitative and qualitative assessments is used to determine the presence and severity of prosthetic TR ( Table 2 ). TR may be either transvalvular or paravalvular in origin, and careful 2D assessment of the prosthetic TV from all available windows is necessary for complete evaluation. In the presence of clinically significant paravalvular regurgitation, percutaneous closure can be considered as a corrective strategy, whereas the extreme situation of “valve rocking,” suggestive of valve dehiscence, represents a contraindication to a ViV procedure. However, quantitation of paravalvular leaks is not established for TV prostheses. One might categorize severity by inferring from aortic valve literature and estimating the proportion of the annular circumference occupied by the leak, but this method has not been validated for TV prostheses. If transvalvular TR is present, transthoracic echocardiographic assessment should include qualitative assessment of TV leaflets (prolapse, flail), failure of leaflet coaptation ( Video 4 , available at www.onlinejase.com ), and quantitative assessment of the regurgitant volume. Severe TR is usually associated with right atrial and RV dilatation, diastolic ventricular septal flattening, IVC dilatation, and hepatic vein systolic flow reversal ( Figure 2 ). On color Doppler imaging, a large flow convergence ( Video 5 , available at www.onlinejase.com ) and increased vena contracta width (>0.7 cm), effective regurgitant orifice area ≥ 40 mm 2 , and regurgitant volume ≥ 45 mL/beat all suggest severe TR, as does a dense CW Doppler tracing with a triangular, early-peaking velocity, and increased transvalvular Doppler measurements (peak velocity and mean gradient). A VTI ratio between the TV prosthesis (VTI PrTV ; CW Doppler derived) and the LVOT (VTI LVOT ; pulsed-wave Doppler derived) of >3.3 in the context of increased transvalvular gradient and normal PHT may help confirm the presence of significant TR. Three-dimensional color Doppler imaging may be also helpful, but its role in quantifying the regurgitant volume has not been extensively evaluated.
| Parameter | Mild | Moderate | Severe |
|---|---|---|---|
| Valve structure | Usually normal | Abnormal or valve dehiscence | Abnormal or valve dehiscence |
| Jet area by color Doppler, central jets only (cm 2 ) | <5 | 5–10 | >10 |
| Vena contracta width (cm) ∗ | Not defined | Not defined, but <0.7 | >0.7 |
| Jet density/contour by CW Doppler | Incomplete or faint, parabolic | Dense, variable contour | Dense with early peaking |
| Doppler systolic hepatic flow | Normal or blunted | Blunted | Holosystolic reversal |
| Right atrium, right ventricle, IVC | Normal † | Dilated | Markedly dilated |
∗ For a valvular TR jet, extrapolated from native TR; unknown cutoffs for paravalvular TR.
† If no other reason for dilatation. Reprinted from Zoghbi WA et al .
Procedural Image Guidance with TEE Imaging
Imaging the TV
The tricuspid annular plane is anterior, almost vertical, and orientated approximately 45° from the sagittal plane. To fully visualize the TV, the American Society of Echocardiography advocates the use of multiple comprehensive TEE windows from multiple depths and plane angles. The midesophageal four-chamber view with simultaneous biplane imaging permits visualization of the septal and anterior TV leaflets ( Figure 3 A), where the anterior leaflet is usually adjacent to the aorta. However, in the midesophageal windows, the TV is in the far field and may be subject to beam widening and attenuation; further insertion of the TEE probe to the distal esophageal, shallow transgastric, and deep transgastric views approximates the TEE probe and the TV, bringing the TV into the near field and optimizing windows of the TV. At the distal esophageal view, the absence of left heart structures from the image allows comprehensive 3D assessment of TV function ( Figure 3 B); in the transgastric views, multiplane imaging (or rotating the probe 60°–90°) produces simultaneous en face visualization of all three TV leaflets ( Figure 3 C) and is an ideal view for differentiating transvalvular TR from paravalvular TR and for diagnosing thrombus or vegetations on the leaflets; in the deep transgastric view, rightward anterior flexion ( Figure 3 D) permits optimal TV color flow and spectral Doppler evaluation of TR jets. It is important to rotate through multiple planes at each TEE level and use simultaneous orthogonal imaging to evaluate the TV comprehensively, to help with identifying leaflets, and to appreciate adjacent anatomy.
