REVIEW URRENT C OPINION
Recent developments in echocardiographic imaging Michele Nanna a and Giovanni Nanna b
Purpose of review This review provides an outline of recent applications related to the use of ultrasonography in various catheter-based procedures for the repair of many valvular abnormalities. Recent findings Percutaneous interventions are becoming a safe and effective therapeutic modality in the management of various valvular defects. The intrinsic ability of ultrasound to provide real-time accurate assessment of cardiac and valvular structural and functional abnormalities makes this modality distinctively useful in the execution of percutaneous valvular procedures and evaluation of their results. Clinical applications of myocardial deformation and cardiac mechanics have been investigated in an increasing number of clinical applications. Speckle tracking accurately measures myocardial deformation parameters and has been recently applied to the evaluation of mitral insufficiency mechanisms. Summary Recent developments in echocardiography are promoting this modality from its traditional role of diagnostic technique into one suitable for aiding in the execution of complex catheter-based procedures and for accurate monitoring of therapeutic response in many clinical settings. Keywords aortic stenosis, mitral valve insufficiency, speckle tracking ultrasound imaging, transcatheter procedures, valve repair
INTRODUCTION Ultrasound techniques have expanded from the realm of diagnostic modalities to applications attached to the performance of percutaneous valvular procedures. Recent developments in ultrasound cardiac imaging and the growing experience with transcatheter valvular interventions have expanded the applications of echocardiographic techniques. As percutaneous intervention gains widespread acceptance in the management of various valvular defects, the use of ultrasound, with its ability to provide real-time assessment of cardiac and valvular structural and functional abnormalities, is becoming a pivotal modality during the performance of percutaneous valvular procedures and in the evaluation of their results. Clinical applications of myocardial deformation and cardiac mechanics have been undergoing continuing investigative scrutiny and have been expanding in scope. Speckle tracking is emerging as a valuable technique in the measurement of myocardial deformation parameters, including the assessment of mitral insufficiency. This review will examine recent progress in echocardiography that has expanded its applications and utility.
USE OF ECHOCARDIOGRAPHY IN PERCUTANEOUS INTERVENTIONS For patients at elevated risk for surgical intervention, options have traditionally been limited to medical therapy, with limited results. The advent of transcatheter techniques for valvular repair or replacement has revolutionized treatment options for these patients with prohibitive surgical risk. For both aortic and mitral valve abnormalities, landmark clinical trials and world registries have begun to define the role of these catheter-based therapeutic modalities, while the development of multidisciplinary heart teams has helped optimize patient treatment pathways and outcomes. The ability of echocardiography to provide rapid and precise assessments of cardiac anatomy and function lends itself conveniently to providing a Albert Einstein College of Medicine, Bronx and bLenox Hill Hospital, New York, New York, USA
Correspondence to Michele Nanna, MD, FACC, Cardiac Care and Vascular Medicine, 1461 Astor Ave, Bronx, NY 10469, USA. Tel: +1 718 881 4891; e-mail: [email protected] Curr Opin Cardiol 2014, 29:417–422 DOI:10.1097/HCO.0000000000000095
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Imaging and echocardiography
KEY POINTS Echocardiography is a test of choice for the assessment of various parameters that are critical in the execution of transcatheter aortic valve procedures. Echocardiography assessment can help in the appropriate sizing of an aortic prosthetic device during TAVR procedures. In the treatment of mitral valve insufficiency an echocardiographically guided percutaneous approach has a safety superior to that of conventional surgical procedures and resulted in similar improvements in clinical outcomes. Although echocardiography remains the test of choice, MRI is feasible and accurate in the evaluation of patients undergoing the MitraClip procedure. The use of echocardiography in the evaluation of patients undergoing mitral valve repair procedures in mitral insufficiency has resulted in a better understanding of the regurgitation mechanism and helped strategize optimal repair techniques.
complementary imaging during complex interventional procedures.
IMAGING IN TRANSCATHETER AORTIC VALVE REPLACEMENT Transcatheter implantation of a prosthetic aortic valve is establishing itself as a safe and reliable procedure that is revolutionizing the clinical approach for patients with aortic valve disease. The role of imaging for the successful execution of this revolutionary technique is intuitive. Intraprocedural ultrasound evaluation and guidance allows the characterization of valve morphology. Estimation of annular size, valve morphology, severity of valvular lesions and the baseline severity of left ventricular size, function and hypertrophy have been traditionally performed using echocardiography. Specific echocardiographic indexes that are related to transcatheter aortic valve replacement (TAVR) include assessment of the distance from the valve to the left main coronary ostium and the angle of the left ventricular outflow tract to the aorta, both critical parameters in planning for this transcatheter procedure. Other imaging techniques still have a role in the preprocedural assessment of patients undergoing TAVR. Computerized tomography (CT) is superior to echocardiography in the evaluation of calcification and complex atheromatous plaques of segments of the aorta distal to the arch that would indicate the choice of a different approach other than femoral catheterization. 418
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Echocardiography remains superior to other imaging modalities in sizing the sinuses of Valsalva and the sinotubular junction, particularly in those instances when the prosthetic device may be anchored to the sinotubular junction [1]. During the TAVR procedure, transesophageal echocardiography (TEE) is the procedure of choice for confirming preoperative data and guiding in the optimal execution of the procedure. For example, TEE guidance is invaluable in positioning the stent inside the aortic annulus: because of the expected 2–4 mm of superior migration during implantation in the starting position the valve should be visualized with approximately 2/3 of its profile inferior to the plane of the annulus with only approximately 30% of the valve structure protruding above it [2]. The roles of TEE and fluoroscopy during the procedure are complementary, as wires and catheters are better visualized by the latter whereas ultrasound can assess valve structure and function more rapidly and repeatedly, without additional radiation exposure. Sizing of the aortic valve prosthesis is of pivotal importance for the success of all TAVR procedures. TAVR devices should be slightly ‘oversized’ for a perfect fit, as undersizing can result in paravalvular regurgitation or even embolization [3,4]. Excessive oversizing is associated with reduced valve durability because of underexpansion of the prosthesis, which can lead to possible conduction disturbances necessitating permanent pacemaker insertion or even annular rupture [5]. Expert consensus documents have stressed the importance of constrained oversizing for anchoring these sutureless prosthetic devices [6]. The decision about perfect fit valve size is also dependent on the presence of valve calcification, which can increase the risk of aortic root rupture and require the use of valve size that does not exceed the annular size. Aortic root size can also be measured by multidetector computer tomography (MDCT). Although this modality has intrinsic limitations, several publications have demonstrated that measurements of mean diameter, circumference and area of the aortic ring by MDCT are more reproducible than echocardiography [7–9]. The use of multimodal imaging can, at times, create more uncertainties regarding the proper prosthetic size [10]. When conflicting results are present, there are strategies using balloon aortic valvuloplasty that can help in the decision making [11–13] by providing direct annular sizing and correct prosthesis selection during the procedure. Although the ventricle is undergoing rapid pacing, a contrast injection of Volume 29 Number 5 September 2014
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the aortic root is performed with the balloon inflated. Although ensuring appropriate position by ascertaining immobility of the maximally inflated balloon and absence of contrast regurgitation, the waist of the balloon will provide annulus size. Additional information provided by this maneuver is the prediction of the position of the often-calcified aortic leaflets against the aortic root wall and the exclusion of coronary ostia obstruction by the same. Proper annular sizing is crucially important when balloon-expandable valves are used, as they force and can change the shape of the native annulus, in contrast to self-expandable valves, which will accommodate, rather than force, the native annulus anatomy.
MITRAL VALVE REPAIR USING MITRAL VALVE DOUBLE ORIFICE INTERVENTION Since its introduction by Alfieri, the double orifice technique for mitral-valve repair, which involves approximation of the mitral leaflets with a suture to create a double orifice, has been gaining acceptance for the treatment of degenerative mitral insufficiency, even as a stand-alone technique and not in combination with a prosthetic annulus implant. This has provided the basis for attempting isolated edge-to-edge mitral-valve repair through a percutaneous intervention that delivers a mechanical device across the interatrial septum. A recent prospective randomized trial [Endovascular Valve Edgeto-Edge Repair Study (EVEREST II)] [14] compared the efficacy and safety of percutaneous mitral valve repair versus a conventional surgical approach. This multicenter trial demonstrated that, while the percutaneous approach did not have the same efficacy as conventional surgical procedures, its safety was actually superior and it resulted in similar improvements in clinical outcomes. In this trial, all parameters of efficacy were graded using standard widely accepted echocardiographic techniques. Other diagnostic modalities have also been employed in the evaluation of patients undergoing percutaneous mitral-valve repair with the MitraClip system. Krumm et al. [15 ] utilized cardiac MRI in 27 consecutive patients with symptomatic moderateto-severe mitral insufficiency undergoing the MitraClip procedure in a prospective study. An extinction artifact was noted around the clip, but this did not influence the evaluation of cardiac function and morphology, thus allowing the authors to conclude that MRI is feasible and accurate in the evaluation of patients undergoing the MitraClip procedure. The study did not compare the accuracy of MRI with that of echocardiography, and therefore &
echocardiography is currently the test of choice for the evaluation of patients undergoing percutaneous mitral double orifice interventions. Echocardiography has been shown to be valuable in the detection of procedural complications of patients undergoing the MitraClip procedure. The procedure involves transseptal puncture and results in a new atrial septal defect (ASD) after withdrawal of the 22Fr guiding catheter. In a study by Hoffmann et al. [16 ], three-dimensional transesophageal echocardiography (3D TEE) used direct en face imaging to measure the area of the new ASD in 28 patients with symptomatic mitral regurgitation undergoing percutaneous mitral valve repair using the MitraClip device. Shunt volume was calculated by measuring velocity time integral across the ASD, and left ventricular inflow volume was calculated using mitral inflow velocity time integral. The investigation demonstrated that the use of the transseptal catheter resulted in a small ASD of 0.19 cm2, which is approximately 44% of the area of the 22-Fr guiding catheter, with a left to right shunt amounting to 14 ml/beat, which may contribute to a pressure relief of the left atrium. This provides a possible mechanism for the observed immediate hemodynamic benefit of the procedure, which is in addition to and augments the benefit of the regurgitant flow reduction. 3D TEE has emerged as the most valuable imaging modality in the evaluation of the mitral valve. The current generation matrix-array technology can provide two-dimensional and threedimensional imaging with a single transducer. 3D TEE allows visualization of the mitral valve and its surrounding structures in real time, and provides detailed anatomical guidance and assessment of functional abnormalities during surgical and transcatheter interventions. The possibility of mitral valve relative stenosis following MitraClip implantation has also been a concern that can be addressed by careful echocardiographic evaluation. Intraprocedural evaluation of the MitraClip implant involves not only the detection of residual mitral valve regurgitation, but also the monitoring of mitral valve diastolic gradient, which may guide the decision making regarding the placement of additional clips. In a study by Boerlage-van Dijk et al. [17 ], intraprocedural hemodynamics were compared with postprocedural parameters and the effect of changing hemodynamics of restrictive flow during exercise. A total of 51 patients undergoing the MitraClip procedure were evaluated retrospectively and 23 of them underwent follow-up exercise echocardiographic evaluation. The intraprocedural mean MVPG was significantly increased from 3.0 1.6 to 4.3 2.2 mmHg
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postprocedure. This increase in the transvalvular postprocedure gradient was more evident during exercise, with a statistically significant increase from 3.6 1.7 during rest conditions to 6.3 2.7 mmHg with exercise. Receiver-operating characteristic curve analysis showed an estimated cut-off point for intraprocedural pressure half-time of 91 ms to identify patients with mitral stenosis and systolic pulmonary artery pressure (sPAP) 50 mmHg postrepair intervention. The results led the authors to conclude that mean MVPG measured intraprocedurally during MitraClip implantation underestimates the hemodynamics of daily life, and this should be considered by operators in the decision making regarding the placement of one or more clips. Pressure half-time seems to be the most robust parameter compared with mean and maximum MVPG and may contribute to this decision. Echocardiography is helpful in the follow-up evaluation of these patients. In a study by Giannini et al. [18 ], echocardiography was used to investigate changes of left (LV) and right ventricular (RV) dimensions after MitraClip procedures performed in 35 high-risk surgical patients with severe mitral insufficiency. Echocardiographic serial evaluation was able to detect reverse remodeling with reduction of LV volumes and improvement of RV systolic functional indices, tricuspid annulus plane systolic excursion and systolic velocity at the tricuspid annulus (RV sm) following successful MitraClip implantation. These data confirm a previous report by Scandura et al. [19], who performed a prospective observational study of 44 consecutive patients at high risk of surgery, with moderate-to-severe or severe mitral regurgitation, undergoing MitraClip system implantation. At 6 months of follow-up, significant reductions of the sphericity index, LV end-diastolic volume index and LV end-systolic volume index were observed with concomitant improvement of LV ejection fraction. Reverse remodeling, according to the specified definition, was observed in 77.3% of the patients. The mechanism of LV reverse remodeling following the MitraClip procedure has been the subject of interesting debate. In a letter to the editor in reference to Scardura’s article, Silbinger [20 ] postulated that MitraClip implantation influences LV remodeling not only by unloading the LV after the correction of mitral regurgitation but also through an independent mechanism involving a proposed mechanism of valvular–ventricular interaction. In this proposed mechanism, a syncytial fibromuscular loop starting from the aortic annular insertion of the epicardial fibers and ending at the right and left fibrous trigones travels to the apex and up to the papillary &
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muscles into the strut chords, which attach to the anterior mitral leaflet. According to Silbiger’s theory, the clip anchoring the two leaflets together would enhance the fibromuscular continuity, exerting a more powerful support system that would promote reverse remodeling. This favorable effect on LV geometry would be more evident in cases in which tethering of the mitral valve apparatus is the primary mechanism of insufficiency. Although there are no validated data supporting the mechanism suggested by Silbiger, available evidence seems to suggest a consistent effectiveness of the MitraClip procedure on the left cardiac chamber’s reverse remodeling with a trend toward greater LV reverse remodeling with the edge-to-edge technique compared with isolated annuloplasty. These considerations emphasize the need for a careful evaluation of the mechanism of mitral insufficiency to apply the correct repair strategy; for example, once an accurate mechanism of insufficiency is established the appropriate best repair modality can be chosen among those targeting the leaflets (leaflet plication, coaptation or ablation), the annulus, the chordae (percutaneous chordal implantation) or the LV (percutaneous LV remodeling), including a potential combination of techniques in cases in which combined anatomic and functional abnormalities are identified.
MITRAL VALVE INSUFFICIENCY Fostered by refined surgical techniques of mitral valve repair, investigative efforts aimed at clarifying the mechanisms of mitral insufficiency, especially mitral insufficiency related to ischemic heart disease, have gathered pace in recent years with the development of readily available new noninvasive assessment techniques. Complex regurgitant jets are usually associated with less satisfactory results after mitral repair. For example, the placement of an undersized mitral ring has the potential to worsen leaflet tethering and coaptation of the posterior mitral leaflet, resulting in persistent insufficiency after surgery. Zeng et al. [21 ] used 3D TEE to examine the quantitative differences in mitral valve geometry between the asymmetric and symmetric tethering patterns in patients with ischemic mitral regurgitation (IMR) and to examine the impact of these quantitative differences and tethering pattern on IMR severity. A symmetric tethering pattern is characterized by apical tethering of both leaflets to a similar degree, resulting in symmetric coaptation and a centrally directed mitral regurgitation jet. An asymmetric tethering pattern with its asymmetric coaptation and a posteriorly directed mitral regurgitation jet predisposes to a greater degree of &
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mitral regurgitation because the asymmetric coaptation is unfavorable for an effective coaptational surface. Despite higher ejection fractions (EFs) and less extensive wall motion abnormalities, the asymmetric group had a greater percentage of severe mitral regurgitation assessed by the integrative method. Therefore, if there is substantial asymmetric tethering resulting from an overtethered posterior leaflet, mitral replacement may be the option of choice. Alternatively, one should consider other surgical procedures, such as localized LV reshaping, papillary muscle repositioning or chordal cutting, that target the subvalvular apparatus in conjunction with ring annuloplasty. A broad discussion of the complex mechanisms of ischemic mitral insufficiency has been the subject of recent review articles. The article by Silbiger [22 ] provides a comprehensive review and explores the possibility that left atrial remodeling may also play a role in the pathogenesis of IMR, through a novel mechanism: atriogenic leaflet tethering. The author proposes that several structural adaptations play a role in reducing IMR. In contrast to the compensatory effects of left ventricular enlargement, these may reduce, rather than increase, its severity. The suggested adaptations involve the mitral valve leaflets, the papillary muscles, the mitral annulus and the left ventricular false tendons. This review describes the potential role each may play in reducing IMR and therapies that exploit these adaptations [22 ]. Recent advances in cardiac imaging techniques, such as speckle-tracking echocardiography, have provided new insights into another possible mechanism for IMR. Zito et al. [23 ] have recently investigated the involvement of impaired basal rotation in the pathophysiology of mitral regurgitation. The study confirmed the presence of more severe regurgitation in patients with inferior posterior basal infarcted segments and in subjects with asymmetric rather than symmetric tethering. Basal radial, circumferential and longitudinal strain and rotation were lower in patients with inferior posterior basal infarcted segments. There was also a significant inverse correlation between effective regurgitant orifice area (EROA) and basal rotation in the latter group, indicating that impaired basal rotational mechanics occurring after an inferior-posterior myocardial infarction is associated with increased mitral regurgitation. Quantification of the mitral valve itself has been the subject of recent investigation using new diagnostic tools. With the development of probe technology and software, real-time 3D echocardiography is capable of acquiring and displaying 3D color flow Doppler imaging. Commercially available &&
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software provides tools for manually tracing regurgitant jet contours, and mitral regurgitation volume can be directly measured. The accuracy of mitral regurgitation volume measurements using directly planimetered EROA by real-time 3D color-Doppler echocardiography multiplied by the mitral regurgitation time velocity integral (TVI) has been tested against mitral regurgitation volume measured by velocity-encoded cardiac magnetic resonance [24,25]. Wang et al. [26 ] evaluated the feasibility and accuracy of 3D directly measured mitral regurgitation volume with mitral regurgitation volume derived from traditional measurements using EROA by real-time 3D color-Doppler echocardiography. Their results demonstrated that, while direct assessment of mitral regurgitation volumes using 3D software was feasible and reproducible, quantification of eccentric mitral regurgitation with this method significantly underestimated the mitral regurgitation volume compared with traditional real-time methods, with a strong correlation noted for the measurement of central jets. Thus, despite technological innovation in imaging, the quantification of eccentric jets remains challenging. &
CONCLUSION The development of catheter-based techniques in the treatment of various valvular abnormalities has promoted the use of ultrasound-based methods from the realm of diagnostic tools to critical modalities in the planning and performance of these procedures. Practitioners involved in the management of patients with valvular abnormalities will be required to be familiar with parameters that relate to the appropriate use and patient suitability for these revolutionary procedures. Future areas of research will focus on the ability of the noninvasive evaluation to predict long-term results using these treatment modalities. Acknowledgements None. Conflicts of interest There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the annual period of review, have been highlighted as: & of special interest && of outstanding interest 1. Grube E, Schuler G, Buellesfeld L, et al. Percutaneous aortic valve replacement for severe aortic stenosis in high risk patients using the second- and current third-generation self-expanding CoreValve prosthesis: device success and 30-day clinical outcome. J Am Coll Cardiol 2007; 50:69–76.
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Imaging and echocardiography 2. Moss RR, Ivens E, Pasupati S, et al. Role of echocardiography in percutaneous aortic valve implantation. JACC Cardiovasc Imaging 2008; 1:15–24. 3. Detaint D, Lepage L, Himbert D, et al. Determinants of significant paravalvular regurgitation after transcatheter aortic valve: implantation impact of device and annulus discongruence. J Am Coll Cardiol Intv 2009; 2:821–827. 4. Tay EL, Gurvitch R, Wijeysinghe N, et al. Outcome of patients after transcatheter aortic valve embolization. JACC Cardiovasc Interv 2011; 4:228– 234. 5. Blanke P, Reinohl J, Schlensak C, et al. Prosthesis oversizing in balloon expandable transcatheter aortic valve implantation is associated with contained rupture of the aortic root. Circ Cardiovasc Interv 2012; 5:540–548. 6. Holmes DR Jr, Mack MJ, Kaul S, et al. 2012 ACCF/AATS/SCAI/STS expert consensus document on transcatheter aortic valve replacement. J Am Coll Cardiol 2012; 59:1200–1254. 7. Messika-Zeitoun D, Serfaty JM, Brochet E, et al. Multimodal assessment of the aortic annulus diameter: implications for transcatheter aortic valve implantation. J Am Coll Cardiol 2010; 55:186–194. 8. Schoenhagen P, Tuzcu EM, Kapadia SR, et al. Three-dimensional imaging of the aortic valve and aortic root with computed tomography: new standards in an era of transcatheter valve repair/implantation. Eur Heart J 2009; 30:2079– 2086. 9. O’Brien B, Schoenhagen P, Kapadia SR, et al. Integration of 3D imaging data in the assessment of aortic stenosis: impact on classification of disease severity. Circ Cardiovasc Imaging 2011; 4:566–573. 10. Cerillo AG, Mariani M, Glauber M, Berti S, et al. Sizing the annulus for transcatheter aortic valve implantation: more than a simple measure? Eur J Cardiothorac Surg 2012; 41:717–718. 11. Babaliaros VC, Liff D, Chen EP, et al. Can balloon aortic valvuloplasty help determine appropriate transcatheter aortic valve size? JACC Cardiovasc Interv 2008; 1:580–586. 12. Babaliaros VC, Junagadhwalla Z, Lerakis S, et al. Use of balloon aortic valvuloplasty to size the aortic annulus before implantation of a balloon-expandable transcatheter heart valve. JACC Cardiovasc Interv 2010; 3:114–118. 13. Cerillo AG, Mariani M, Berti S, Glauber M. Sizing the aortic annulus. Ann Cardiothorac Surg 2012; 1:245–256. 14. Feldman T, Foster E, Glower DD, et al., EVEREST II Investigators. Percutaneous Repair or Surgery for Mitral Regurgitation. N Engl J Med 2011; 364:1395– 1406. 15. Krumm P, Zuern CS, Wurster TH, et al. Cardiac magnetic resonance imaging & in patients undergoing percutaneous mitral valve repair with the MitraClip system. Clin Res Cardiol 2014; 103:397–404. A study demonstrating that MRI is feasible and accurate in the evaluation of patients undergoing the MitraClip procedure. This investigation is widely referenced as one of the few that have established the effectiveness of methodologies alternative to ultrasound in the follow-up of patients undergoing the MitraClip procedure. 16. Hoffmann R, Altiok E, Reith S, et al. Functional effect of new atrial septal && defect after percutaneous mitral valve repair using the MitraClip device. Am J Cardiol 2014; 113:1228–1233. A study using 3D TEE to measure the area of the new ASD in 28 patients with symptomatic mitral regurgitation undergoing percutaneous mitral valve repair using the MitraClip procedure. This important study provides a detailed analysis of a commonly observed consequence of the MitraClip procedure. 17. Boerlage-van Dijk K, van Riel ACMJ, de Bruin-Bon RHACM, et al. Mitral inflow && patterns after MitraClip implantation at rest and during exercise. J Am Soc Echocardiogr 2014; 27:24–31. This study investigates a potential complication of MitraClip implant: the development of relative mitral stenosis. The authors provided a detailed analysis of this important complication and established the importance of diastolic transvalvular gradient in guiding the placement of additional clips.
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18. Giannini C, Petronio AS, De Carlo M, et al. Integrated reverse left and right ventricular remodeling after MitraClip implantation in functional mitral regurgitation: an echocardiographic study. Eur Heart J Cardiovasc Imaging 2013; 15:95–103. In this study, serial echocardiographic evaluation detected reverse remodeling with reduction of LV volumes and improvement of RV systolic functional indices, tricuspid annulus plane systolic excursion and systolic velocity at the tricuspid annulus (RV sm) following successful MitraClip implantation. A comprehensive analysis of the effect of MitraClip implant on various parameters of right and left ventricular functions. 19. Scandura S, Ussia GP, Capranzano P, et al. Left cardiac chambers reverse remodeling after percutaneous mitral valve repair with the MitraClip system. J Am Soc Echocardiogr 2012; 25:1099–1105. 20. Silbinger JJ. A novel mechanism by which MitraClip implantation may favorably & alter the natural history of left ventricular remodeling in patients with mitral regurgitation: proposed role of the ventricular-valvular loop. J Am Soc Echocardiogr 2013; 26:217–219. Letter to the editor postulating an interesting mechanism to explain reverse left ventricular remodeling after transcatheter correction of mitral regurgitation. An interesting perspective argued by one of the foremost experts in the field. 21. Zeng X, Carmo M, Nunes P, et al. Asymmetric versus symmetric tethering & patterns in ischemic mitral regurgitation: geometric differences from threedimensional transesophageal echocardiography. J Am Soc Echocardiogr 2014; 27:367–375. This article describes quantitative differences in mitral valve geometry between asymmetric and symmetric tethering patterns in patients with ischemic mitral regurgitation. This is an interesting investigation that describes one important variant of the many mechanisms underlying the presence of mitral insufficiency. 22. Silbiger JJ. Novel pathogenetic mechanisms and structural adaptations && in ischemic mitral regurgitation. J Am Soc Echocardiogr 2013; 26:1107– 1117. An interesting article providing a comprehensive description of the pathogenetic mechanisms of mitral insufficiency. A must-read article describing the various mechanisms related to ischemic mitral insufficiency. Particularly relevant to all those involved in the decision making regarding the modality of mitral valve repair. 23. Zito C, Cusma-Piccione M, Oreto L, et al. In patients with post-infarction left & ventricular dysfunction, how does impaired basal rotation affect chronic ischemic mitral regurgitation? J Am Soc Echocardiogr 2013; 26:1118– 1129. An article investigating the use of speckle-tracking echocardiography in providing new insights into possible mechanisms for IMR. This investigation makes use of a novel ultrasound modality to shed light on a potential mechanism of ischemic mitral insufficiency. 24. Marsan NA, Westenberg JJ, Ypenburg C, et al. Quantification of functional mitral regurgitation by real time 3D echocardiography: comparison with 3D velocity-encoded cardiac magnetic resonance. JACC Cardiovasc Imaging 2009; 2:1245–1252. 25. Shanks M, Siebelink HM, Delgado V, et al. Quantitative assessment of mitral regurgitation: comparison between three-dimensional transesophageal echocardiography and magnetic resonance imaging. Circ Cardiovasc Imaging 2010; 3:694–700. 26. Wang W, Lin Q, Wu W, et al. Quantification of mitral regurgitation by general & imaging three-dimensional quantification: feasibility and accuracy. J Am Soc Echocardiogr 2014; 27:268–276. A study evaluating feasibility and accuracy of directly measured mitral regurgitation volume using 3D echocardiography compared with mitral regurgitation volume derived from traditional color-Doppler echocardiography measurements. An interesting publication validating the accuracy of directly 3D measured regurgitant volume. &
Volume 29 Number 5 September 2014
Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Recent developments in echocardiographic imaging Michele Nanna a and Giovanni Nanna b
Purpose of review This review provides an outline of recent applications related to the use of ultrasonography in various catheter-based procedures for the repair of many valvular abnormalities. Recent findings Percutaneous interventions are becoming a safe and effective therapeutic modality in the management of various valvular defects. The intrinsic ability of ultrasound to provide real-time accurate assessment of cardiac and valvular structural and functional abnormalities makes this modality distinctively useful in the execution of percutaneous valvular procedures and evaluation of their results. Clinical applications of myocardial deformation and cardiac mechanics have been investigated in an increasing number of clinical applications. Speckle tracking accurately measures myocardial deformation parameters and has been recently applied to the evaluation of mitral insufficiency mechanisms. Summary Recent developments in echocardiography are promoting this modality from its traditional role of diagnostic technique into one suitable for aiding in the execution of complex catheter-based procedures and for accurate monitoring of therapeutic response in many clinical settings. Keywords aortic stenosis, mitral valve insufficiency, speckle tracking ultrasound imaging, transcatheter procedures, valve repair
INTRODUCTION Ultrasound techniques have expanded from the realm of diagnostic modalities to applications attached to the performance of percutaneous valvular procedures. Recent developments in ultrasound cardiac imaging and the growing experience with transcatheter valvular interventions have expanded the applications of echocardiographic techniques. As percutaneous intervention gains widespread acceptance in the management of various valvular defects, the use of ultrasound, with its ability to provide real-time assessment of cardiac and valvular structural and functional abnormalities, is becoming a pivotal modality during the performance of percutaneous valvular procedures and in the evaluation of their results. Clinical applications of myocardial deformation and cardiac mechanics have been undergoing continuing investigative scrutiny and have been expanding in scope. Speckle tracking is emerging as a valuable technique in the measurement of myocardial deformation parameters, including the assessment of mitral insufficiency. This review will examine recent progress in echocardiography that has expanded its applications and utility.
USE OF ECHOCARDIOGRAPHY IN PERCUTANEOUS INTERVENTIONS For patients at elevated risk for surgical intervention, options have traditionally been limited to medical therapy, with limited results. The advent of transcatheter techniques for valvular repair or replacement has revolutionized treatment options for these patients with prohibitive surgical risk. For both aortic and mitral valve abnormalities, landmark clinical trials and world registries have begun to define the role of these catheter-based therapeutic modalities, while the development of multidisciplinary heart teams has helped optimize patient treatment pathways and outcomes. The ability of echocardiography to provide rapid and precise assessments of cardiac anatomy and function lends itself conveniently to providing a Albert Einstein College of Medicine, Bronx and bLenox Hill Hospital, New York, New York, USA
Correspondence to Michele Nanna, MD, FACC, Cardiac Care and Vascular Medicine, 1461 Astor Ave, Bronx, NY 10469, USA. Tel: +1 718 881 4891; e-mail: [email protected] Curr Opin Cardiol 2014, 29:417–422 DOI:10.1097/HCO.0000000000000095
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Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Imaging and echocardiography
KEY POINTS Echocardiography is a test of choice for the assessment of various parameters that are critical in the execution of transcatheter aortic valve procedures. Echocardiography assessment can help in the appropriate sizing of an aortic prosthetic device during TAVR procedures. In the treatment of mitral valve insufficiency an echocardiographically guided percutaneous approach has a safety superior to that of conventional surgical procedures and resulted in similar improvements in clinical outcomes. Although echocardiography remains the test of choice, MRI is feasible and accurate in the evaluation of patients undergoing the MitraClip procedure. The use of echocardiography in the evaluation of patients undergoing mitral valve repair procedures in mitral insufficiency has resulted in a better understanding of the regurgitation mechanism and helped strategize optimal repair techniques.
complementary imaging during complex interventional procedures.
IMAGING IN TRANSCATHETER AORTIC VALVE REPLACEMENT Transcatheter implantation of a prosthetic aortic valve is establishing itself as a safe and reliable procedure that is revolutionizing the clinical approach for patients with aortic valve disease. The role of imaging for the successful execution of this revolutionary technique is intuitive. Intraprocedural ultrasound evaluation and guidance allows the characterization of valve morphology. Estimation of annular size, valve morphology, severity of valvular lesions and the baseline severity of left ventricular size, function and hypertrophy have been traditionally performed using echocardiography. Specific echocardiographic indexes that are related to transcatheter aortic valve replacement (TAVR) include assessment of the distance from the valve to the left main coronary ostium and the angle of the left ventricular outflow tract to the aorta, both critical parameters in planning for this transcatheter procedure. Other imaging techniques still have a role in the preprocedural assessment of patients undergoing TAVR. Computerized tomography (CT) is superior to echocardiography in the evaluation of calcification and complex atheromatous plaques of segments of the aorta distal to the arch that would indicate the choice of a different approach other than femoral catheterization. 418
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Echocardiography remains superior to other imaging modalities in sizing the sinuses of Valsalva and the sinotubular junction, particularly in those instances when the prosthetic device may be anchored to the sinotubular junction [1]. During the TAVR procedure, transesophageal echocardiography (TEE) is the procedure of choice for confirming preoperative data and guiding in the optimal execution of the procedure. For example, TEE guidance is invaluable in positioning the stent inside the aortic annulus: because of the expected 2–4 mm of superior migration during implantation in the starting position the valve should be visualized with approximately 2/3 of its profile inferior to the plane of the annulus with only approximately 30% of the valve structure protruding above it [2]. The roles of TEE and fluoroscopy during the procedure are complementary, as wires and catheters are better visualized by the latter whereas ultrasound can assess valve structure and function more rapidly and repeatedly, without additional radiation exposure. Sizing of the aortic valve prosthesis is of pivotal importance for the success of all TAVR procedures. TAVR devices should be slightly ‘oversized’ for a perfect fit, as undersizing can result in paravalvular regurgitation or even embolization [3,4]. Excessive oversizing is associated with reduced valve durability because of underexpansion of the prosthesis, which can lead to possible conduction disturbances necessitating permanent pacemaker insertion or even annular rupture [5]. Expert consensus documents have stressed the importance of constrained oversizing for anchoring these sutureless prosthetic devices [6]. The decision about perfect fit valve size is also dependent on the presence of valve calcification, which can increase the risk of aortic root rupture and require the use of valve size that does not exceed the annular size. Aortic root size can also be measured by multidetector computer tomography (MDCT). Although this modality has intrinsic limitations, several publications have demonstrated that measurements of mean diameter, circumference and area of the aortic ring by MDCT are more reproducible than echocardiography [7–9]. The use of multimodal imaging can, at times, create more uncertainties regarding the proper prosthetic size [10]. When conflicting results are present, there are strategies using balloon aortic valvuloplasty that can help in the decision making [11–13] by providing direct annular sizing and correct prosthesis selection during the procedure. Although the ventricle is undergoing rapid pacing, a contrast injection of Volume 29 Number 5 September 2014
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the aortic root is performed with the balloon inflated. Although ensuring appropriate position by ascertaining immobility of the maximally inflated balloon and absence of contrast regurgitation, the waist of the balloon will provide annulus size. Additional information provided by this maneuver is the prediction of the position of the often-calcified aortic leaflets against the aortic root wall and the exclusion of coronary ostia obstruction by the same. Proper annular sizing is crucially important when balloon-expandable valves are used, as they force and can change the shape of the native annulus, in contrast to self-expandable valves, which will accommodate, rather than force, the native annulus anatomy.
MITRAL VALVE REPAIR USING MITRAL VALVE DOUBLE ORIFICE INTERVENTION Since its introduction by Alfieri, the double orifice technique for mitral-valve repair, which involves approximation of the mitral leaflets with a suture to create a double orifice, has been gaining acceptance for the treatment of degenerative mitral insufficiency, even as a stand-alone technique and not in combination with a prosthetic annulus implant. This has provided the basis for attempting isolated edge-to-edge mitral-valve repair through a percutaneous intervention that delivers a mechanical device across the interatrial septum. A recent prospective randomized trial [Endovascular Valve Edgeto-Edge Repair Study (EVEREST II)] [14] compared the efficacy and safety of percutaneous mitral valve repair versus a conventional surgical approach. This multicenter trial demonstrated that, while the percutaneous approach did not have the same efficacy as conventional surgical procedures, its safety was actually superior and it resulted in similar improvements in clinical outcomes. In this trial, all parameters of efficacy were graded using standard widely accepted echocardiographic techniques. Other diagnostic modalities have also been employed in the evaluation of patients undergoing percutaneous mitral-valve repair with the MitraClip system. Krumm et al. [15 ] utilized cardiac MRI in 27 consecutive patients with symptomatic moderateto-severe mitral insufficiency undergoing the MitraClip procedure in a prospective study. An extinction artifact was noted around the clip, but this did not influence the evaluation of cardiac function and morphology, thus allowing the authors to conclude that MRI is feasible and accurate in the evaluation of patients undergoing the MitraClip procedure. The study did not compare the accuracy of MRI with that of echocardiography, and therefore &
echocardiography is currently the test of choice for the evaluation of patients undergoing percutaneous mitral double orifice interventions. Echocardiography has been shown to be valuable in the detection of procedural complications of patients undergoing the MitraClip procedure. The procedure involves transseptal puncture and results in a new atrial septal defect (ASD) after withdrawal of the 22Fr guiding catheter. In a study by Hoffmann et al. [16 ], three-dimensional transesophageal echocardiography (3D TEE) used direct en face imaging to measure the area of the new ASD in 28 patients with symptomatic mitral regurgitation undergoing percutaneous mitral valve repair using the MitraClip device. Shunt volume was calculated by measuring velocity time integral across the ASD, and left ventricular inflow volume was calculated using mitral inflow velocity time integral. The investigation demonstrated that the use of the transseptal catheter resulted in a small ASD of 0.19 cm2, which is approximately 44% of the area of the 22-Fr guiding catheter, with a left to right shunt amounting to 14 ml/beat, which may contribute to a pressure relief of the left atrium. This provides a possible mechanism for the observed immediate hemodynamic benefit of the procedure, which is in addition to and augments the benefit of the regurgitant flow reduction. 3D TEE has emerged as the most valuable imaging modality in the evaluation of the mitral valve. The current generation matrix-array technology can provide two-dimensional and threedimensional imaging with a single transducer. 3D TEE allows visualization of the mitral valve and its surrounding structures in real time, and provides detailed anatomical guidance and assessment of functional abnormalities during surgical and transcatheter interventions. The possibility of mitral valve relative stenosis following MitraClip implantation has also been a concern that can be addressed by careful echocardiographic evaluation. Intraprocedural evaluation of the MitraClip implant involves not only the detection of residual mitral valve regurgitation, but also the monitoring of mitral valve diastolic gradient, which may guide the decision making regarding the placement of additional clips. In a study by Boerlage-van Dijk et al. [17 ], intraprocedural hemodynamics were compared with postprocedural parameters and the effect of changing hemodynamics of restrictive flow during exercise. A total of 51 patients undergoing the MitraClip procedure were evaluated retrospectively and 23 of them underwent follow-up exercise echocardiographic evaluation. The intraprocedural mean MVPG was significantly increased from 3.0 1.6 to 4.3 2.2 mmHg
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postprocedure. This increase in the transvalvular postprocedure gradient was more evident during exercise, with a statistically significant increase from 3.6 1.7 during rest conditions to 6.3 2.7 mmHg with exercise. Receiver-operating characteristic curve analysis showed an estimated cut-off point for intraprocedural pressure half-time of 91 ms to identify patients with mitral stenosis and systolic pulmonary artery pressure (sPAP) 50 mmHg postrepair intervention. The results led the authors to conclude that mean MVPG measured intraprocedurally during MitraClip implantation underestimates the hemodynamics of daily life, and this should be considered by operators in the decision making regarding the placement of one or more clips. Pressure half-time seems to be the most robust parameter compared with mean and maximum MVPG and may contribute to this decision. Echocardiography is helpful in the follow-up evaluation of these patients. In a study by Giannini et al. [18 ], echocardiography was used to investigate changes of left (LV) and right ventricular (RV) dimensions after MitraClip procedures performed in 35 high-risk surgical patients with severe mitral insufficiency. Echocardiographic serial evaluation was able to detect reverse remodeling with reduction of LV volumes and improvement of RV systolic functional indices, tricuspid annulus plane systolic excursion and systolic velocity at the tricuspid annulus (RV sm) following successful MitraClip implantation. These data confirm a previous report by Scandura et al. [19], who performed a prospective observational study of 44 consecutive patients at high risk of surgery, with moderate-to-severe or severe mitral regurgitation, undergoing MitraClip system implantation. At 6 months of follow-up, significant reductions of the sphericity index, LV end-diastolic volume index and LV end-systolic volume index were observed with concomitant improvement of LV ejection fraction. Reverse remodeling, according to the specified definition, was observed in 77.3% of the patients. The mechanism of LV reverse remodeling following the MitraClip procedure has been the subject of interesting debate. In a letter to the editor in reference to Scardura’s article, Silbinger [20 ] postulated that MitraClip implantation influences LV remodeling not only by unloading the LV after the correction of mitral regurgitation but also through an independent mechanism involving a proposed mechanism of valvular–ventricular interaction. In this proposed mechanism, a syncytial fibromuscular loop starting from the aortic annular insertion of the epicardial fibers and ending at the right and left fibrous trigones travels to the apex and up to the papillary &
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muscles into the strut chords, which attach to the anterior mitral leaflet. According to Silbiger’s theory, the clip anchoring the two leaflets together would enhance the fibromuscular continuity, exerting a more powerful support system that would promote reverse remodeling. This favorable effect on LV geometry would be more evident in cases in which tethering of the mitral valve apparatus is the primary mechanism of insufficiency. Although there are no validated data supporting the mechanism suggested by Silbiger, available evidence seems to suggest a consistent effectiveness of the MitraClip procedure on the left cardiac chamber’s reverse remodeling with a trend toward greater LV reverse remodeling with the edge-to-edge technique compared with isolated annuloplasty. These considerations emphasize the need for a careful evaluation of the mechanism of mitral insufficiency to apply the correct repair strategy; for example, once an accurate mechanism of insufficiency is established the appropriate best repair modality can be chosen among those targeting the leaflets (leaflet plication, coaptation or ablation), the annulus, the chordae (percutaneous chordal implantation) or the LV (percutaneous LV remodeling), including a potential combination of techniques in cases in which combined anatomic and functional abnormalities are identified.
MITRAL VALVE INSUFFICIENCY Fostered by refined surgical techniques of mitral valve repair, investigative efforts aimed at clarifying the mechanisms of mitral insufficiency, especially mitral insufficiency related to ischemic heart disease, have gathered pace in recent years with the development of readily available new noninvasive assessment techniques. Complex regurgitant jets are usually associated with less satisfactory results after mitral repair. For example, the placement of an undersized mitral ring has the potential to worsen leaflet tethering and coaptation of the posterior mitral leaflet, resulting in persistent insufficiency after surgery. Zeng et al. [21 ] used 3D TEE to examine the quantitative differences in mitral valve geometry between the asymmetric and symmetric tethering patterns in patients with ischemic mitral regurgitation (IMR) and to examine the impact of these quantitative differences and tethering pattern on IMR severity. A symmetric tethering pattern is characterized by apical tethering of both leaflets to a similar degree, resulting in symmetric coaptation and a centrally directed mitral regurgitation jet. An asymmetric tethering pattern with its asymmetric coaptation and a posteriorly directed mitral regurgitation jet predisposes to a greater degree of &
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mitral regurgitation because the asymmetric coaptation is unfavorable for an effective coaptational surface. Despite higher ejection fractions (EFs) and less extensive wall motion abnormalities, the asymmetric group had a greater percentage of severe mitral regurgitation assessed by the integrative method. Therefore, if there is substantial asymmetric tethering resulting from an overtethered posterior leaflet, mitral replacement may be the option of choice. Alternatively, one should consider other surgical procedures, such as localized LV reshaping, papillary muscle repositioning or chordal cutting, that target the subvalvular apparatus in conjunction with ring annuloplasty. A broad discussion of the complex mechanisms of ischemic mitral insufficiency has been the subject of recent review articles. The article by Silbiger [22 ] provides a comprehensive review and explores the possibility that left atrial remodeling may also play a role in the pathogenesis of IMR, through a novel mechanism: atriogenic leaflet tethering. The author proposes that several structural adaptations play a role in reducing IMR. In contrast to the compensatory effects of left ventricular enlargement, these may reduce, rather than increase, its severity. The suggested adaptations involve the mitral valve leaflets, the papillary muscles, the mitral annulus and the left ventricular false tendons. This review describes the potential role each may play in reducing IMR and therapies that exploit these adaptations [22 ]. Recent advances in cardiac imaging techniques, such as speckle-tracking echocardiography, have provided new insights into another possible mechanism for IMR. Zito et al. [23 ] have recently investigated the involvement of impaired basal rotation in the pathophysiology of mitral regurgitation. The study confirmed the presence of more severe regurgitation in patients with inferior posterior basal infarcted segments and in subjects with asymmetric rather than symmetric tethering. Basal radial, circumferential and longitudinal strain and rotation were lower in patients with inferior posterior basal infarcted segments. There was also a significant inverse correlation between effective regurgitant orifice area (EROA) and basal rotation in the latter group, indicating that impaired basal rotational mechanics occurring after an inferior-posterior myocardial infarction is associated with increased mitral regurgitation. Quantification of the mitral valve itself has been the subject of recent investigation using new diagnostic tools. With the development of probe technology and software, real-time 3D echocardiography is capable of acquiring and displaying 3D color flow Doppler imaging. Commercially available &&
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software provides tools for manually tracing regurgitant jet contours, and mitral regurgitation volume can be directly measured. The accuracy of mitral regurgitation volume measurements using directly planimetered EROA by real-time 3D color-Doppler echocardiography multiplied by the mitral regurgitation time velocity integral (TVI) has been tested against mitral regurgitation volume measured by velocity-encoded cardiac magnetic resonance [24,25]. Wang et al. [26 ] evaluated the feasibility and accuracy of 3D directly measured mitral regurgitation volume with mitral regurgitation volume derived from traditional measurements using EROA by real-time 3D color-Doppler echocardiography. Their results demonstrated that, while direct assessment of mitral regurgitation volumes using 3D software was feasible and reproducible, quantification of eccentric mitral regurgitation with this method significantly underestimated the mitral regurgitation volume compared with traditional real-time methods, with a strong correlation noted for the measurement of central jets. Thus, despite technological innovation in imaging, the quantification of eccentric jets remains challenging. &
CONCLUSION The development of catheter-based techniques in the treatment of various valvular abnormalities has promoted the use of ultrasound-based methods from the realm of diagnostic tools to critical modalities in the planning and performance of these procedures. Practitioners involved in the management of patients with valvular abnormalities will be required to be familiar with parameters that relate to the appropriate use and patient suitability for these revolutionary procedures. Future areas of research will focus on the ability of the noninvasive evaluation to predict long-term results using these treatment modalities. Acknowledgements None. Conflicts of interest There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the annual period of review, have been highlighted as: & of special interest && of outstanding interest 1. Grube E, Schuler G, Buellesfeld L, et al. Percutaneous aortic valve replacement for severe aortic stenosis in high risk patients using the second- and current third-generation self-expanding CoreValve prosthesis: device success and 30-day clinical outcome. J Am Coll Cardiol 2007; 50:69–76.
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Imaging and echocardiography 2. Moss RR, Ivens E, Pasupati S, et al. Role of echocardiography in percutaneous aortic valve implantation. JACC Cardiovasc Imaging 2008; 1:15–24. 3. Detaint D, Lepage L, Himbert D, et al. Determinants of significant paravalvular regurgitation after transcatheter aortic valve: implantation impact of device and annulus discongruence. J Am Coll Cardiol Intv 2009; 2:821–827. 4. Tay EL, Gurvitch R, Wijeysinghe N, et al. Outcome of patients after transcatheter aortic valve embolization. JACC Cardiovasc Interv 2011; 4:228– 234. 5. Blanke P, Reinohl J, Schlensak C, et al. Prosthesis oversizing in balloon expandable transcatheter aortic valve implantation is associated with contained rupture of the aortic root. Circ Cardiovasc Interv 2012; 5:540–548. 6. Holmes DR Jr, Mack MJ, Kaul S, et al. 2012 ACCF/AATS/SCAI/STS expert consensus document on transcatheter aortic valve replacement. J Am Coll Cardiol 2012; 59:1200–1254. 7. Messika-Zeitoun D, Serfaty JM, Brochet E, et al. Multimodal assessment of the aortic annulus diameter: implications for transcatheter aortic valve implantation. J Am Coll Cardiol 2010; 55:186–194. 8. Schoenhagen P, Tuzcu EM, Kapadia SR, et al. Three-dimensional imaging of the aortic valve and aortic root with computed tomography: new standards in an era of transcatheter valve repair/implantation. Eur Heart J 2009; 30:2079– 2086. 9. O’Brien B, Schoenhagen P, Kapadia SR, et al. Integration of 3D imaging data in the assessment of aortic stenosis: impact on classification of disease severity. Circ Cardiovasc Imaging 2011; 4:566–573. 10. Cerillo AG, Mariani M, Glauber M, Berti S, et al. Sizing the annulus for transcatheter aortic valve implantation: more than a simple measure? Eur J Cardiothorac Surg 2012; 41:717–718. 11. Babaliaros VC, Liff D, Chen EP, et al. Can balloon aortic valvuloplasty help determine appropriate transcatheter aortic valve size? JACC Cardiovasc Interv 2008; 1:580–586. 12. Babaliaros VC, Junagadhwalla Z, Lerakis S, et al. Use of balloon aortic valvuloplasty to size the aortic annulus before implantation of a balloon-expandable transcatheter heart valve. JACC Cardiovasc Interv 2010; 3:114–118. 13. Cerillo AG, Mariani M, Berti S, Glauber M. Sizing the aortic annulus. Ann Cardiothorac Surg 2012; 1:245–256. 14. Feldman T, Foster E, Glower DD, et al., EVEREST II Investigators. Percutaneous Repair or Surgery for Mitral Regurgitation. N Engl J Med 2011; 364:1395– 1406. 15. Krumm P, Zuern CS, Wurster TH, et al. Cardiac magnetic resonance imaging & in patients undergoing percutaneous mitral valve repair with the MitraClip system. Clin Res Cardiol 2014; 103:397–404. A study demonstrating that MRI is feasible and accurate in the evaluation of patients undergoing the MitraClip procedure. This investigation is widely referenced as one of the few that have established the effectiveness of methodologies alternative to ultrasound in the follow-up of patients undergoing the MitraClip procedure. 16. Hoffmann R, Altiok E, Reith S, et al. Functional effect of new atrial septal && defect after percutaneous mitral valve repair using the MitraClip device. Am J Cardiol 2014; 113:1228–1233. A study using 3D TEE to measure the area of the new ASD in 28 patients with symptomatic mitral regurgitation undergoing percutaneous mitral valve repair using the MitraClip procedure. This important study provides a detailed analysis of a commonly observed consequence of the MitraClip procedure. 17. Boerlage-van Dijk K, van Riel ACMJ, de Bruin-Bon RHACM, et al. Mitral inflow && patterns after MitraClip implantation at rest and during exercise. J Am Soc Echocardiogr 2014; 27:24–31. This study investigates a potential complication of MitraClip implant: the development of relative mitral stenosis. The authors provided a detailed analysis of this important complication and established the importance of diastolic transvalvular gradient in guiding the placement of additional clips.
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18. Giannini C, Petronio AS, De Carlo M, et al. Integrated reverse left and right ventricular remodeling after MitraClip implantation in functional mitral regurgitation: an echocardiographic study. Eur Heart J Cardiovasc Imaging 2013; 15:95–103. In this study, serial echocardiographic evaluation detected reverse remodeling with reduction of LV volumes and improvement of RV systolic functional indices, tricuspid annulus plane systolic excursion and systolic velocity at the tricuspid annulus (RV sm) following successful MitraClip implantation. A comprehensive analysis of the effect of MitraClip implant on various parameters of right and left ventricular functions. 19. Scandura S, Ussia GP, Capranzano P, et al. Left cardiac chambers reverse remodeling after percutaneous mitral valve repair with the MitraClip system. J Am Soc Echocardiogr 2012; 25:1099–1105. 20. Silbinger JJ. A novel mechanism by which MitraClip implantation may favorably & alter the natural history of left ventricular remodeling in patients with mitral regurgitation: proposed role of the ventricular-valvular loop. J Am Soc Echocardiogr 2013; 26:217–219. Letter to the editor postulating an interesting mechanism to explain reverse left ventricular remodeling after transcatheter correction of mitral regurgitation. An interesting perspective argued by one of the foremost experts in the field. 21. Zeng X, Carmo M, Nunes P, et al. Asymmetric versus symmetric tethering & patterns in ischemic mitral regurgitation: geometric differences from threedimensional transesophageal echocardiography. J Am Soc Echocardiogr 2014; 27:367–375. This article describes quantitative differences in mitral valve geometry between asymmetric and symmetric tethering patterns in patients with ischemic mitral regurgitation. This is an interesting investigation that describes one important variant of the many mechanisms underlying the presence of mitral insufficiency. 22. Silbiger JJ. Novel pathogenetic mechanisms and structural adaptations && in ischemic mitral regurgitation. J Am Soc Echocardiogr 2013; 26:1107– 1117. An interesting article providing a comprehensive description of the pathogenetic mechanisms of mitral insufficiency. A must-read article describing the various mechanisms related to ischemic mitral insufficiency. Particularly relevant to all those involved in the decision making regarding the modality of mitral valve repair. 23. Zito C, Cusma-Piccione M, Oreto L, et al. In patients with post-infarction left & ventricular dysfunction, how does impaired basal rotation affect chronic ischemic mitral regurgitation? J Am Soc Echocardiogr 2013; 26:1118– 1129. An article investigating the use of speckle-tracking echocardiography in providing new insights into possible mechanisms for IMR. This investigation makes use of a novel ultrasound modality to shed light on a potential mechanism of ischemic mitral insufficiency. 24. Marsan NA, Westenberg JJ, Ypenburg C, et al. Quantification of functional mitral regurgitation by real time 3D echocardiography: comparison with 3D velocity-encoded cardiac magnetic resonance. JACC Cardiovasc Imaging 2009; 2:1245–1252. 25. Shanks M, Siebelink HM, Delgado V, et al. Quantitative assessment of mitral regurgitation: comparison between three-dimensional transesophageal echocardiography and magnetic resonance imaging. Circ Cardiovasc Imaging 2010; 3:694–700. 26. Wang W, Lin Q, Wu W, et al. Quantification of mitral regurgitation by general & imaging three-dimensional quantification: feasibility and accuracy. J Am Soc Echocardiogr 2014; 27:268–276. A study evaluating feasibility and accuracy of directly measured mitral regurgitation volume using 3D echocardiography compared with mitral regurgitation volume derived from traditional color-Doppler echocardiography measurements. An interesting publication validating the accuracy of directly 3D measured regurgitant volume. &
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