Transcatheter Aortic Valve Replacement: Still in the Way of Learning

Dear Editors,

We have read with great interest and gratitude the recent manuscript published in the Journal of Invasive Cardiology by Toggweiler et al entitled, “Natural Course of Paravalvular Regurgitation After Implantation of the Self-Expanding CoreValve: Insights From Serial TEE Measurements.”

Since the beginning of percutaneous aortic valve replacement, the prevention and quantification of aortic regurgitation have been the Achilles’ heel for all those cardiologists and radiologists involved in this matter.^1,2

Although there has been a progressive increase in percutaneous prosthesis implantation, definite criteria for the correct quantification of aortic regurgitation have not yet been established. Otherwise, several aspects must be taken into account for a successful procedure. First, the correct selection of patients with a careful annulus measure is essential. Next, preprocedural predictors of aortic regurgitation must be established. Finally, a careful procedure with transesophageal echocardiography monitoring can guarantee a successful result.

Regarding the annulus size, and as Tuzcu et al³ wrote before, its correct measure is clearly “more complex that it appears.” Discrepancies among the different imaging modalities have been explained by the fact that each method seems to measure a different part of the annulus. At this moment, multislice computed tomography is recognized as the best technique, not only for studying the annulus size but also because it allows the recognition of predictors of aortic regurgitation. Shultz et al were pioneers in the use of computed tomography, and its reproducibility has been clearly demonstrated; in fact, computed tomography is the most complete technique. Later on, Kasel et al’s magnificent manuscript, “Standardized Imaging of the Aortic Root,” correlated different CT measures with the annulus range provided by the manufacturers of the Edwards (Edwards Lifesciences) and CoreValve (Medtronic, Inc) prostheses. Recently, Wang et al published a comparison of aortic annulus size by transesophageal echocardiography and computed tomography, concluding that combining measurements from both techniques would be the best option.⁴ 

Furthermore, since aortic regurgitation is the Achilles’ heel of this procedure, the predictors of paravalvular leak are welcome. At the moment, two parameters seem to be the most important to take into account: maximal aortic annulus diameter and severity of leaflet calcification, both of which can be easily assessed by the Agatston score. As Martino et al concluded, the latter is the only independent predictor of paravalvular leak. 

As cardiologists and radiologists, we think that we are still in the way of learning about transcatheter aortic valves and we really appreciate any information about them; a precise preprocedure annulus measurement is essential, but at the same time, predictors of aortic regurgitation must be taken into account in the decision-making process, and finally, we must know how to assess a proper quantification of the aortic regurgitation during the procedure. So, as Tuzcu et al said before, we also think that it is still more complex than it appears.

References 

1.    Toggweiler S, van Schie B, Zuber M, et al. Natural course of paravalvular regurgitation after implantation of the self-expanding CoreValve: insights from serial TEE measurements. J Invasive Cardiol. 2015;27:435-440.

2.    Di Martino LF, Vletter WB, Ren B, et al. Prediction of paravalvular leakage after transcatheter aortic valve implantation. Int J Cardiovasc Imaging. 2015;31:1461-1468.

3.    Tuzcu EM, Kapadia SR, Schoenhagen P. Multimodality quantitative imaging of aortic root for transcatheter aortic valve implantation: more complex than it appears. J Am Coll Cardiol. 2010;55:195-197. 

4.    Wang H, Hanna JM, Ganapathi A, et al. Comparison of aortic annulus size by transesophageal echocardiography and computed tomography angiography with direct surgical measurement. Am J Cardiol. 2015;115:1568-1573. 

Authors’ Response

We would like to thank Martin et al for their interest in our manuscript and their thoughtful comments.¹ We agree that the aortic annulus is a complex structure. Current imaging techniques are able to provide reproducible information about the anatomy, and the degree and extent of calcification of the annulus. Perhaps we have to rely on different imaging modalities and may be able to identify the best transcatheter heart valve for each individual patient. In Europe, there are currently seven transcatheter heart valves (THVs) with CE mark, and many centers routinely implant 2-3 different valves. Ask yourself which THV you would implant in a patient with

•    A horizontal root.

•    A heavily calcified annulus.

•    A heavily calcified annulus with calcification extending     into the left ventricular outflow tract.

•    A low origin of the left main coronary artery and heavy calcification of the left coronary cusp.

•    A true bicuspid, calcified aortic valve.

•    Severe aortic regurgitation, uncalcified leaflets, but absence of relevant annular dilatation.

We will be able to provide better answers to these questions in the near future, as two- and three-dimensional imaging technology will continue to improve. In that sense, we agree with Martin et al: we are still in the way of learning.

Sincerely,

Stefan Toggweiler, MD¹; Michel Zuber, MD²; Thomas F. Lüscher, MD²

The ¹Cardiology, Heart Center Lucerne, Luzerner Kantonsspital, Lucerne, Switzerland; and the ²Heart Center, University Hospital Zurich, Zurich, Switzerland.

Disclosure: Dr Toggweiler received speaker fees from Medtronic and Edwards Lifesciences and serves as a proctor for Symetis.

Address for correspondence: Stefan Toggweiler, MD, Heart Center Lucerne, Luzerner Kantonsspital. Email: stefan.toggweiler@luks.ch

_______________________________________________

From the ¹Cardiology and ²Radiology Departments, Hospital Universitario Central de Asturias, Oviedo, Spain.

Manuscript submitted October 7, 2015, final version accepted October 19, 2015.

Address for correspondence: María Martín, MD, PhD, Avda Pedro Masaveu 27, 4L, Oviedo, Asturias, Spain. Email: mmartinf7@hotmail.com