Surgical repair of the mitral valve complex presents high mortality rates, strongly dependent on the surgical procedure. Intensity and polarization sensitive OCT are explored as a feasible degradation inspection method for rheumatic and degenerative chords.This work is supported by the “Ministerio de Economía, Industria y Competitividad” (MINECO) under projects DA2TOI (FIS2010-19860), SENSA (TEC2016-76021-C2-2-R), IDIVAL under project DiCuTen (INNVAL16/02) and the “Instituto de Salud Carlos III” (ISCIII) through projects FUSIODERM (DTS15/00238) and CIBERBBN and the co -financed by FEDER funds

Calvo Díez, Marta

Conde Portilla, Olga María

López Higuera, José Miguel

Pontón Cortina, Alejandro

Real Peña, Eusebio

Revuelta Soba, José Manuel

Eusebio Real

José M. Revuelta

Alejandro Pontón

Marta Calvo-Díez

José M. López-Higuera

Olga M. Conde

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OCT inspection of degenerative and rheumatic tendinous cords

UCrea

PROGRESS IN BIOMEDICAL OPTICS AND IMAGING Vol. 18 No. 60      Volume 10411   Proceedings of SPIE-OSA Biomedical Optics, 1605-7422, V. 10411 SPIE is an international society advancing an interdisciplinary approach to the science and application of light. Clinical and Preclinical Optical Diagnostics    J. Quincy Brown Ton G. van Leeuwen Editors     25–27 June 2017 Munich, Germany   Sponsored by The Optical Society (United States) SPIE   Published by  SPIE    Clinical and Preclinical Optical Diagnostics, edited by J. Quincy Brown, Ton G. van Leeuwen,Proc. of SPIE-OSA Vol. 10411, 1041101 · © 2017 OSA-SPIECCC code: 1605-7422/17/$18 · doi: 10.1117/12.2292243Proc. of SPIE-OSA Vol. 10411  1041101-1Downloaded From: https://www.spiedigitallibrary.org/conference-proceedings-of-spie on 10/17/2017 Terms of Use: https://spiedigitallibrary.spie.org/ss/TermsOfUse.aspxThe papers in this volume were part of the technical conference cited on the cover and title page. 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Box 10, Bellingham, Washington 98227-0010 USA Telephone +1 360 676 3290 (Pacific Time)· Fax +1 360 647 1445 SPIE.org and The Optical Society  2010 Massachusetts Ave., N.W., Washington, D.C., 20036 USA Telephone 1 202/223-8130 (Eastern Time)· Fax 1 202/223-1096 http://www.osa.org  Copyright © 2017, Society of Photo-Optical Instrumentation Engineers and The Optical Society   Copying of material in this book for internal or personal use, or for the internal or personal use of specific clients, beyond the fair use provisions granted by the U.S. Copyright Law is authorized by SPIE subject to payment of copying fees. The Transactional Reporting Service base fee for this volume is $18.00 per article (or portion thereof), which should be paid directly to the Copyright Clearance Center (CCC), 222 Rosewood Drive, Danvers, MA 01923. Payment may also be made electronically through CCC Online at copyright.com. Other copying for republication, resale, advertising or promotion, or any form of systematic or multiple reproduction of any material in this book is prohibited except with permission in writing from the publisher. The CCC fee code is 1605-7422/17/$18.00.  Printed in the United States of America.  Publication of record for individual papers is online in the SPIE Digital Library.  SPIEDigitalLibrary.org Paper Numbering: Proceedings of SPIE follow an e-First publication model. A unique citation identifier (CID) number is assigned to each article at the time of publication. Utilization of CIDs allows articles to be fully citable as soon as they are published online, and connects the same identifier to all online and print versions of the publication. SPIE uses a seven-digit CID article numbering system structured as follows: The first five digits correspond to the SPIE volume number.        The last two digits indicate publication order within the volume using a Base 36 numbering system employing both numerals and letters. These two-number sets start with 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 0A, 0B … 0Z, followed by 10-1Z, 20-2Z, etc. The CID Number appears on each page of the manuscript.  Proc. of SPIE-OSA Vol. 10411  1041101-2Downloaded From: https://www.spiedigitallibrary.org/conference-proceedings-of-spie on 10/17/2017 Terms of Use: https://spiedigitallibrary.spie.org/ss/TermsOfUse.aspx      OCT inspection of degenerative and rheumatic tendinous cords  Eusebio Real*a, José M. Revueltab, Alejandro Pontónc, Marta Calvo-Díezc, José M. López-Higueraa,d, Olga M. Condea,d,e aPhotonics Engineering Group, Dep. TEISA, University of Cantabria, 39005 Santander, Spain; bMedical and Surgical Sciences Department. Faculty of Medicine. University of Cantabria, 39011 Santander, Spain; cCardiovascular Surgery Service. Marqués de Valdecilla University Hospital, 39008 Santander, Spain; dCIBERBBN, Av. Monforte de Lemos 3-5,28029 Madrid, Spain;  eIDIVAL, Avenida Cardenal Herrera Oria s/n,39011 Santander ABSTRACT   Surgical repair of the mitral valve complex presents high mortality rates, strongly dependent on the surgical procedure. Intensity and polarization sensitive OCT are explored as a feasible degradation inspection method for rheumatic and degenerative chords. Keywords: optical coherence tomography, mitral valve, tendinous cords, degenerative mitral valve disease, rheumatic mitral valve disease 1. INTRODUCTION  Degenerative mitral valve disease, rheumatic mitral valve disease, endocarditis and ischemic mitral valve disease are the principal pathologies affecting the mitral valve and the valvar complex [1]. Defects on the mitral valve complex imply blood regurgitation from the left ventricle to the atrium, causing blood pressure and volume increase in the left side of the heart. Once the disease is detected, the mitral valve complex must be repaired or replaced by a mechanical prosthesis [2]. Surgical guidelines have been established to assess the best treatment on each scenario [3]. The procedure depends on the pathology itself and on the elements of the valve affected, but it is strongly influenced by the health conditions, risk factors and age of the patient.  Mitral valve repair is preferred to mitral valve replacement as it reduces operative mortality [4]. More conservative interventions imply a better prognostic, reducing recovering time and symptoms and extending the reoperation rate. However, all the affected valve components should be excised in the first intervention, as future reoperations increase the mortality rate considerably: around 5% mortality after the first intervention, 7% after the second and 17% after the third intervention. In case of emergency surgery, these rates are of around 20%, 30% and 40% respectively [4]. On the one side, excising all the affected tissue is vital. On the other side, the reduction of the excised tissue, if under healthy conditions, improves the prognosis and reduces mortality rate. This is especially relevant in cases of endocarditis, affected by infection of the heart tissue, and rheumatic valve, where the cords and valve present calcium deposits and can be fully calcified tissue.  Tendinous cords are formed by a dense collagen core, surrounded by a spongy collagen and elastin layer. Under healthy conditions, cords present parallel and homogenous distribution of collagen bundles. When cords become pathological, the elastin amount increases breaking the collagen bundles, mucopolysaccharides fill the gaps of collagen and, in some cases, also calcium deposits appear. Degradation of the cords can affect the core, the spongy layer or both [5]. When only the core is affected, it remains hidden during surgical repair from the surgeon viewpoint. Therefore, a diagnosis tool will be desirable to assess the pathological status of the tendinous cords under intraoperative scenarios with the cord diagnosis provided within the surgery workflow.  Optical Coherence Tomography (OCT) and Polarization Sensitive Optical Coherence Tomography (PS-OCT) are proposed to evaluate the cross section of the tendinous cords. OCT provides information about tissue structure and homogeneity, highlighting elements with different refractive indexes and attenuation coefficients.   *eusebio.real@unican.es; phone +34 942 200 877-12;   Clinical and Preclinical Optical Diagnostics, edited by J. Quincy Brown, Ton G. van Leeuwen,Proc. of SPIE-OSA Vol. 10411, 104110W · © 2017 OSA-SPIECCC code: 1605-7422/17/$18 · doi: 10.1117/12.2283039Proc. of SPIE-OSA Vol. 10411  104110W-1Downloaded From: http://proceedings.spiedigitallibrary.org/pdfaccess.ashx?url=/data/conferences/spiep/93299/ on 08/02/2017 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx      PS-OCT is sensitive to the phase delay produced by birefringent tissues, such as ordered fibers of collagen [6]. The combination of both techniques can provide accurate information for the characterization of different components in the cords, such as collagen, mucopolysaccharides and calcium deposits.  2. MATERIALS AND METHODS  Human tendinous cords from the mitral valve are excised from a donor and from two patients intervened of degenerative mitral valve disease and rheumatic mitral valve disease. Measured cords are diagnosed by an experienced cardiovascular surgeon. Specimens are preserved in a 1% solution of glutaraldehyde at a temperature of 7ºC upon OCT measurements and at 23ºC during the measurement. The OCT system is Thorlabs OCS1300SS, working at 1325nm with 100nm FWHM. The imaging region is of 10 mm x 3 mm lateral by depth. Penetration is digitalized with 512 pixels for 3mm, which for tendinous cords (n≈1.3897 measured in the OCT images [7]) is reduced to 2.158 mm. Lateral dimension is digitalized in 1024 pixels (phase image) and 4096 pixels (intensity image). Phase retardation is digitalized from 0º to 180º in steps of 0.7º.   The fringes present in the phase image are due to the birefringence of the collagenous tissue. This affects differently the horizontal and vertical components of the detected signal, producing a phase difference from 0º to 180º. The birefringence of the specimens is obtained from the phase retardation information following Equation 1, where z is the period of fringes and λ0 the OCT center wavelength [6]: example  zz 2200    (1) 3. RESULTS AND DISCUSSION Control specimen exhibits homogeneous intensity levels (Fig. 1a, 1d). The fringes effect in the intensity image is an artifact due to tissue birefringence in the OCT dual channel detection. Tissue shows a homogeneous texture, produced by the cross section imaging of collagen bundles. This is maintained along the whole chord. Phase retardation shows a robust parallel fringe pattern in depth (Fig. 1g). This is due to the parallel and uniform distribution of collagen in all the circumference of the cord. In the case of rheumatic specimen intensity images (Fig. 1b, 1e), the fringes pattern is not present on the surface, which corresponds to calcified tissue. In the phase retardation image (Fig. 1h), the fringes pattern is present below the surface, corresponding to the core of collagen. Despite being covered with a calcified spongy layer, the core shows normal collagen composition. The degenerative specimen (Fig. 1c) is likely to the normal one, but showing smaller radius. Looking at the longitudinal cut (Fig. 1f), there are some intensity anomalies apart from the intensity fringes. These anomalies correspond to tissue remodeling after the self-repair of internal damage, alternating collagen parallel distribution [8]. The phase retardation (Fig. 1i) is regular, but blurred when compared to the control one. Proc. of SPIE-OSA Vol. 10411  104110W-2Downloaded From: http://proceedings.spiedigitallibrary.org/pdfaccess.ashx?url=/data/conferences/spiep/93299/ on 08/02/2017 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspxControl Rheumatic Degenerativeo Intensity colormap 255 0° Phase colormap 180°       Figure 1. OCT images corresponding with a control chord (left column), rheumatic chord (center column) and degenerative chord (center column). Intensity OCT is used to produce a transversal section of the chords (a, b, c). Intensity (d, e, f) and polarization sensitive (g, h, i) OCT are used to produce co-registered longitudinal section of the chords.  The birefringence parameter is calculated from the phase retardation in (Fig. 1g, 1h, 1i) according to Equation 1. The control specimen presents a birefringence, obtained from Figure 1g of δ=3.3·10-3. Rheumatic presents δ=2.8·10- and degenerative presents δ=2.6·10-3. The birefringence in the pathological chords is slightly smaller than the control sample, due to collagen loss and remodeling. 4. CONCLUSIONS Intensity OCT and PS-OCT have been used to characterize and compare tendinous cords from human mitral valves. Healthy cords show homogeneous intensity distribution and strong parallel phase patterns. Rheumatic and degenerative specimens show weaker birefringence patterns and less homogeneity. The birefringence pattern in those two cases is lower than in the control sample. The combination of both OCT techniques allows visualization of the core of the tendinous cords, providing useful structural information. In the case of rheumatic tissue, the core of the cord can be correctly imaged and the birefringence parameter obtained. This technique can potentially help surgeons during intervention, giving a deeper insight of the condition of the valvar complex. ACKNOWLEDGMENTS This work is supported by the “Ministerio de Economía, Industria y Competitividad” (MINECO) under projects DA2TOI (FIS2010-19860), SENSA (TEC2016-76021-C2-2-R), IDIVAL under project DiCuTen (INNVAL16/02) and the “Instituto de Salud Carlos III” (ISCIII) through projects FUSIODERM (DTS15/00238) and CIBERBBN and the co-financed by FEDER funds.  Proc. of SPIE-OSA Vol. 10411  104110W-3Downloaded From: http://proceedings.spiedigitallibrary.org/pdfaccess.ashx?url=/data/conferences/spiep/93299/ on 08/02/2017 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx      REFERENCES [1] S.L. Mick, S. Keshavamurthy and A.M. Gillinov, “Mitral valve repair versus replacement,” Annals of Cardiovascular Surgery,4(3),230-237 (2015) [2] Revuelta, J.M., García, R., Gaite, L., Val, F. and Garijo, F.,“Generation of chordae tendineae with polytetrafluoroethylene stents: Results of mitral valve chordae replacement in sheep” Journal of Thoracic Cardiovascular Surgery, 103(97)98-103 (1989) [3] R.A. Nishimura, C.M. Otto, R.O. Bonow, B.A. Carabello, J.P. Erwin 3rd, R.A. Guyton, P.T. O'Gara, C.E. Ruiz, N.J. Skubas, P. Sorajja, T.M. Sundt 3rd, J.D. Thomas and ACC/AHA Task Force Members. “2014 AHA/ACC Guideline for the Management of Patients With Valvular Heart Disease: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines.,” Circulation,129(23), 2440-2492 (2014)  [4] J.M. Revuelta, “La reparación de la insuficiencia mitral entre 2 orillas. Mitral valve repair between 2 shores,” Cirujía Cardiovascular, 22(1), 5-9 (2015)  [5] J.M. Icardo, E. Colvee. and J.M. Revuelta,”Structural analysis of chordae tendineae in degenerative disease of the mitral valve,” International Journal of Cardiology, 167(4), 1603-1609 (2012) [6] J.F. de Boer, T.E. Milner, M.J. van Gemert and J.S. Nelson,”Two-dimensional birefringence imaging in biological tissue by polarization-sensitive optical coherence tomography,” Optics Letters, 22(12), 934-936 (1997) [7] G.J. Tearney, M.E. Brezinski, J.F. Southern, B.E. Bouma, M.R. Hee, and J.G. Fujimoto,”Determination of the refractive index of highly scattering human tissue by optical coherence tomography,” Optics Letters, 20(21), 2258-2260 (1995) [8] P. Whittaker, D.R. Boughner, D.G. Perkins and P.B. Canham,”Quantitative structural analysis of collagen in chordae tendineae and its relation to floppy mitral valves and proteoglycan infiltration” British Heart Journal, 57(3), 264–269 (1987)  Proc. of SPIE-OSA Vol. 10411  104110W-4Downloaded From: http://proceedings.spiedigitallibrary.org/pdfaccess.ashx?url=/data/conferences/spiep/93299/ on 08/02/2017 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx

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OCT inspection of degenerative and rheumatic tendinous cords

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