A 67-year-old man is undergoing mitral valve replacement for rheumatic mitral stenosis with a mechanical prosthetic valve. After separation from cardiopulmonary bypass (CPB), an eccentric mitral regurgitation jet was noted, originating from outside the prosthetic sewing ring. Further evaluation was pursued.
Paravalvular regurgitation or leak (PVL) is a complication associated with the implantation of a prosthetic heart valve. PVL represents pathologic regurgitation originating outside the sewing ring because of incomplete apposition of the prosthetic valve against the native annulus. The incidence of PVL is approximately 15% immediately after elective valve replacement; long-term incidence of PVL may be higher.1 Although most PVLs do not require surgical intervention, a severe PVL may cause heart failure symptoms or hemolytic anemia from turbulence.2 Late PVL results from suture dehiscence, whereas early PVL relates to surgical technique and usually presents in the operating room.3 Factors associated with PVL include the use of biological valves, prolonged CPB time, preoperative atrial fibrillation, heavy valvular or annular calcification, repeat valve surgery, and transcatheter aortic valve replacement (TAVR).4,5
Questions that arise after separation from CPB after valve deployment in TAVR or during any comprehensive assessment of prosthetic valves by transesophageal echocardiography (TEE) are as follows: (1) Is there a PVL and where is it located? (2) How severe is the leak? and (3) Does it require immediate correction?
IS THERE A PVL AND WHERE IS IT LOCATED?
A complete assessment of prosthetic valves by TEE integrates 2D imaging, color flow Doppler (CFD), spectral Doppler, and 3D imaging.5 CFD is paramount because it (1) demonstrates the presence of regurgitant jets, (2) differentiates PVL from intravalvular regurgitation, (3) describes the number, location, and flow direction of the regurgitant jets, and (4) allows evaluation of elements of the regurgitant jet such as vena contracta (VC),width and area, and extent of the jet in the receiving chamber.
Definitive evaluation for the presence and severity of PVL should be performed after separation from CPB, under adequate hemodynamic conditions. However, “screening” for a PVL is feasible once the aortic cross clamp is removed and during periods of partial CPB. After establishing the presence of regurgitation, the next step is to differentiate the PVL from normal “functional” intravalvular regurgitation. Intravalvular regurgitation originates from within the sewing ring, which can be identified on TEE as an echo-dense structure encircling the prosthetic leaflets. It has high acoustic impedance resulting in distal shadowing along the path of the ultrasound beam. Bioprosthetic valves commonly exhibit trace or mild intravalvular central regurgitation,6 whereas mechanical valves generate “washing jets” at the junction of the valve occluders or between the occluders and the valve housing. The washing jets attenuate thrombus formation on the underside of the valve. Although these normal jets may divide into 2 to 3 “plumes” and are usually centrally directed, the number and direction of plumes seen by TEE can vary significantly (Fig. 1).5 These functional intravalvular regurgitation jets are narrow, of low velocity demonstrated by homogeneous color on CFD, and do not extend far beyond the plane of the prosthetic valve.5 Of note, immediately after separation from CPB, there may also be “pathological” intravalvular regurgitation due to sutures, debris, or subvalvular apparatus, which obstruct the normal closing of the prosthetic valve leaflets.
Small PVL jets may be identified immediately after separation from CPB. They commonly originate at the site of annular sutures and resolve with administration of protamine. Significant PVL exhibits a mosaic color pattern consistent with high velocity, turbulent blood flow. Communicating the location and characteristics of PVL to the surgical team is of paramount importance, because with reinstitution of CPB the evaluation of the precise etiology may be more difficult in an unloaded heart.
Known limitations of intraoperative TEE pertaining to the grading of PVL stem from the hemodynamic effects of general anesthesia, positive pressure ventilation, and transient myocardial depression after CPB. These factors may contribute to reduced velocities by CFD because of reduced transvalvular pressure gradients and may result in underestimation of the severity of a PVL. It is important to note that CFD assessment may be limited by technical factors, such as color gain, Nyquist limit, and temporal resolution. Care should be taken to set the Nyquist limit on CFD at 50 to 60 cm/s; too low a Nyquist limit may create the appearance of excessive turbulence and PVL overestimation. Temporal resolution (i.e., frame rate) should be maximized by decreasing the depth and the width of the CFD sector. Color gain should be set to minimize random color noise from the surrounding tissues.
Mitral Prosthetic Valves
TEE is the criterion standard diagnostic method for PVL in the mitral position because of unobstructed views of the valve and annulus in the near-field in the mid-esophageal imaging planes. The entire sewing ring of the mitral prosthesis should be imaged at the mid-esophageal level by slowly sweeping the multiplane angle from 0° to 180° while keeping the prosthetic valve in the center of the image. Off-axis and non-standard views in conjunction with withdrawing/advancing and right/left rotation are sometimes required (Fig. 2; Supplemental Digital Content 1, Video 1, http://links.lww.com/AA/B167; and Supplemental Digital Content 2, Video 2, http://links.lww.com/AA/B168). Two-dimensional echocardiography can identify gross structural abnormalities associated with PVL, such as dehiscence, mechanical instability of the prosthetic mitral valve (“rocking motion”), and vegetations.
By providing en face views of the mitral valve, 3D and 3D with CFD can evaluate more precisely the location and characteristics of the PVL. Gated acquisition of 3D CFD can partially overcome the low temporal resolution of this imaging modality. For both 2D and 3D assessment, the location of the mitral valve PVL can be classified with respect to the aortic valve and the left atrial appendage7 (Fig. 3). Another way of describing location of PVL is by using the position of the native mitral leaflets scallops on the mitral valve annulus as anatomic landmarks.
Aortic Prosthetic Valves
Evaluation of prosthetic valves in the aortic position includes imaging at the mid-esophageal and transgastric level (Fig. 4; Supplemental Digital Content 3, Video 3, http://links.lww.com/AA/B169). Long-axis views, whether mid-esophageal (ME LAX) or transgastric, are limited, because they image 2 opposing points of the prosthetic ring and therefore may miss jets originating outside the imaged plane. In the transgastric views, shadowing artifacts caused by the prosthesis is located distal to the aortic valve and left ventricular outflow tract (LVOT), thereby enabling evaluation of aortic regurgitation by CFD. The circumference of the sewing ring can be visualized in the short axis orientation at the mid-esophageal level. However, subtle probe manipulation is required to ensure precise imaging at the level of the sewing ring. This can be aided by simultaneous imaging of orthogonal planes using a matrix array. Acoustic shadowing from the prosthetic valve itself may obscure imaging of the anterior sewing ring at the mid-esophageal level.8 The location of an aortic PVL can be classified with respect to the position of the cusps of the native aortic valve.
PVL after TAVR is a common finding. At least trivial or mild PVL has been reported in up to 70% of post-TAVR patients.8 A recent meta-analysis reported an overall incidence of moderate or severe PVL after TAVR between 11.7% and 13.9% associated with increased 1-year and 30-day mortality.9 The same imaging views can be used for assessment and grading of paravalvular and intravalvular regurgitation after TAVR. It is important to note that transient, nonpathological central regurgitation often occurs as a result of guidewire placement across the new aortic valve.
Tricuspid and Pulmonary Prosthetic Valves
There are limited data regarding PVL in tricuspid and pulmonary positions. Because of their anterior position, imaging by TEE is difficult. Prosthetic valves in either the tricuspid or pulmonary positions can be imaged at the mid-esophageal and transgastric level in the views used to visualize the respective native valves. The location of the PVL can be identified with respect to the position of the native leaflets/cusps usually seen in those views.
HOW SEVERE IS THE PVL?
Some of the criteria used for native valve regurgitation can be used for quantification of PVL. However, no single parameter should be applied in isolation.
Mitral Prosthetic Valve
In assessing the severity of mitral PVL, CFD-derived parameters are important. Commonly used parameters in this setting are the width of the VC and regurgitant jet area in the left atrium. The width of the VC (Fig. 2; Supplemental Digital Content 1, Video 1, http://links.lww.com/AA/B167; and Supplemental Digital Content 2, Video 2, http://links.lww.com/AA/B168) correlates well with angiographic grading of the severity of PVL.5 Jet area may underestimate the severity of PVL if the regurgitant jet is eccentric and disperses along (“hugs”) the left atrial wall. VC width also has limitations. It measures a single dimension of an otherwise geometrically complex regurgitant orifice and has a narrow range for quantitation. Therefore, small differences in measurements can change the PVL severity grade.
Doppler-derived parameters can be used as indirect markers of significant mitral PVL. An increased transmitral peak early velocity (E velocity >1.9 m/s, suggestive of elevated left atrial pressure) in the presence of a normal pressure half-time (PHT <150 milliseconds, denoting the absence of prosthetic valve stenosis) is suggestive of significant regurgitation. In addition, a high ratio of the velocity-time integral (VTI) across the prosthetic mitral valve to the VTI across the LVOT (VTIMV/VTILVOT > 2.2, denoting that not all the flow across the mitral valve is ejected systemically) is similarly indicative of significant regurgitation in mechanical mitral prosthetic valves10 (Fig. 5A). The cutoff values for different parameters are presented in Table 1.
The utility of novel 3D techniques has been tested for quantification of severity of mitral PVL. Multiplane reconstruction of 3D with CFD data sets can assist in determining the regurgitant orifice shape and effective regurgitant orifice area of the PVL at the level of the sewing ring. Proposed best predictive values for detecting moderate or greater mitral PVL in a recent retrospective study are (1) 3D color major diameter of the regurgitant orifice ≥0.65 cm and (2) 3D color effective regurgitant orifice area ≥0.13 cm211 (Fig. 6). Further prospective studies are needed to confirm these findings.
Aortic Prosthetic Valve
Aortic PVL is primarily graded by the circumferential extent of the neck of the PVL jet compared with the total circumference of the sewing ring as seen by the Mid-Esophageal Short Axis (ME AV SAX) view (Fig. 4; Supplemental Digital Content 3, Video 3, http://links.lww.com/AA/B169). The cutoffs for mild, moderate, and severe PVL are <10%, 10% to 20%, and >20% of the sewing ring circumference, respectively.5 A “rocking” prosthesis is associated with ring dehiscence and with PVL encompassing >40% of the sewing ring circumference.12 Care should be taken to image the neck of the regurgitant jet in short axis at the level of the sewing ring; simultaneous multiplanar imaging can be used to ensure that the orthogonal plane is at the level of the sewing ring. It is important to note that, in the setting of multiple PVLs, the grading by summing of circumferential extent of noncontiguous jets is not additive. This is particularly common with TAVR. In these instances, a combination of parameters, including diastolic flow reversal in the descending thoracic aorta and total regurgitant, volume, should be used.
Semiquantitative and quantitative parameters, validated for regurgitation of the native valve, can be applied. These include VC, jet width/LVOT width ratio, PHT, and diastolic flow reversal in the descending thoracic aorta (Fig. 5, B and C). VC is easy to use but has limitations.5 Acoustic shadowing in the long-axis views and eccentric or multiple jets reduce the applicability of VC or jet width/LVOT width ratio. Table 2 contains cutoff values for the most common parameters used for evaluation of aortic valve regurgitation.
Defining the extent of post TAVR PVL is important because it may prompt the surgical team to balloon dilate the existing valve or perform a “valve-in-valve” TAVR. Current guidelines, exclusive of those for surgical AVR, published by the Valve Academic Research Consortium-2 consensus document (VARC-2), suggest a semiquantitative grading of PVL after TAVR by the circumferential extent of PVL to prosthesis circumference (Fig. 4; Supplemental Digital Content 3, Video 3, http://links.lww.com/AA/B169), with cutoffs of <10% (mild), 10% to 29% (moderate), and ≥30% (severe).13 Calcifications, imaging artifacts, and noncontiguous multiple PVL jets may lead to overestimation of regurgitation.
Tricuspid and Pulmonary Valve Prosthesis
There are no validated echocardiographic parameters for evaluation of tricuspid or pulmonary PVL. However, in the presence of a PVL identified by 2D and CFD, a combination of transtricuspid peak E velocity ≥2.1 m/s, VTITV/VTILVOT ≥3.3, PHT < 200 milliseconds is suggestive of significant regurgitation in a bioprosthetic tricuspid valve.14 Other supportive signs are large jet area, large VC by CFD, and dense spectral Doppler of the regurgitant jet with early peaking velocity.15
DOES THE PVL REQUIRE IMMEDIATE CORRECTION?
A return to CPB because of inadequate valve repair or PVL based on echo findings occurs in 2% to 6%.16 Moderate or severe PVL should trigger surgical intervention, while the management of mild PVL is controversial because it often runs a benign course.5 In a study following 608 patients, 113 (18.3%) had trivial-mild PVL at the conclusion of surgery. At 6 weeks, less than half of these patients had detectable PVL by TTE. Only 1 patient (0.9%) had worsening PVL at 6 weeks or at > 2 years follow-up.17 The decision for immediate correction is complex, requires a team approach, and should be weighed against the risk of prolonged surgery and aortic cross-clamp time; the decision should be tailored to each patient and clinical situation.
* Knowledge of the normal patterns of intravalvular regurgitation and identification of the origin of the regurgitant jet in relation to the sewing ring are paramount in differentiating PVL from intravalvular regurgitation. An integrated approach is required for the diagnosis of PVL with multiplane imaging, spectral Doppler, 3D and, most importantly, CFD in each of the relevant tomographic views.
* Circumferential extent of PVL to prosthetic ring perimeter is the primary modality for grading PVL in the aortic position (surgical or TAVR). Subtle probe manipulations or the use of simultaneous orthogonal plane imaging should ensure that the evaluation of the PVL is done at the level of the sewing ring.
* Diagnosis of mitral PVL is primarily based on VC measurement. Other supporting Doppler parameters suggestive of increased flow across the prosthetic valve are an increased E velocity and high TVI ratio in the presence of a normal PHT.
Name: Ryan Konoske, MD.
Contribution: This author helped write the manuscript.
Attestation: Ryan Konoske approved the final manuscript.
Name: George Whitener, MD.
Contribution: This author helped write the manuscript.
Attestation: George Whitener approved the final manuscript.
Name: Alina Nicoara, MD, FASE.
Contribution: This author helped write the manuscript.
Attestation: Alina Nicoara approved the final manuscript.
This manuscript was handled by: Martin J. London, MD.
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