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Assessment of Systolic and Diastolic Function Vta Tissue Doppler Echocardiography in Boxers

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Assessment of Systolic and Diastolic Function Vta Tissue Doppler Echocardiography in Boxers ASSESSMENT OF SYSTOLIC AND DIASTOLIC FUNCTION VTA TISSUE DOPPLER ECHOCARDIOGRAPHY IN BOXERS AFFECTED WITH ARVC COMPARED TO NORMAL BOXERS AND NON-BOXER CONTROL DOGS A Thesis Presented to The Faculty of Graduate Studies of The University of Guelph by JEREMY ORR In partial fulfilment of requirements for the degree of Doctor of Veterinary Science February, 2011 © Jeremy Orr, 2011 Library and Archives Bibliotheque et 1*1 Canada Archives Canada Published Heritage Direction du Branch Patrimoine de I'edition 395 Wellington Street 395, rue Wellington Ottawa ON K1A 0N4 OttawaONK1A0N4 Canada Canada Your We Votre reference ISBN: 978-0-494-82828-1 Our file Notre reference ISBN: 978-0-494-82828-1 NOTICE: AVIS: The author has granted a non­ L'auteur a accorde une licence non exclusive exclusive license allowing Library and permettant a la Bibliotheque et Archives Archives Canada to reproduce, Canada de reproduire, publier, archiver, publish, archive, preserve, conserve, sauvegarder, conserver, transmettre au public communicate to the public by par telecommunication ou par I'Internet, preter, telecommunication or on the Internet, distribuer et vendre des theses partout dans le loan, distribute and sell theses monde, a des fins commerciales ou autres, sur worldwide, for commercial or non­ support microforme, papier, electronique et/ou commercial purposes, in microform, autres formats. paper, electronic and/or any other formats. The author retains copyright L'auteur conserve la propriete du droit d'auteur ownership and moral rights in this et des droits moraux qui protege cette these. Ni thesis. Neither the thesis nor la these ni des extraits substantiels de celle-ci substantial extracts from it may be ne doivent etre imprimes ou autrement printed or otherwise reproduced reproduits sans son autorisation. without the author's permission. In compliance with the Canadian Conformement a la loi canadienne sur la Privacy Act some supporting forms protection de la vie privee, quelques may have been removed from this formulaires secondaires ont ete enleves de thesis. cette these. While these forms may be included Bien que ces formulaires aient inclus dans in the document page count, their la pagination, il n'y aura aucun contenu removal does not represent any loss manquant. of content from the thesis. 1+1 Canada ABSTRACT ASSESSMENT OF SYSTOLIC AND DIASTOLIC FUNCTION VIA TISSUE DOPPLER ECHOCARDIOGRAPHY IN BOXERS AFFECTED WITH ARVC COMPARED TO NORMAL BOXERS AND NON-BOXER CONTROL DOGS Jeremy Orr Advisor: University of Guelph, 2011 Dr. M. Lynne O'Sullivan This thesis is an investigation of cardiac function in Boxer dogs affected by Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC]. ARVC is the most common acquired cardiac disease reported in the Boxer breed. It is characterized by ventricular arrhythmia of right ventricular origin, resulting in clinical signs of syncope, exercise intolerance, congestive heart failure and sudden death. Structurally, ARVC in the Boxer is characterized by infiltration of the right ventricular myocardium with fibrofatty tissue, which is believed to the arrhythmogenic substrate. Diagnosis of the disease currently relies on the use of Holter monitors, however given the inherent variability associated with Holters, false negatives can occur. Therefore, adjunctive diagnostic modalities are needed to aid in the diagnosis of ARVC-suspected dogs that have inconclusive Holter recordings. Our objectives were to assess both systolic and diastolic function using Tissue Doppler echocardiography (TDI) measured at the medial and lateral mitral valve annulus and the lateral tricuspid valve annulus in Boxers affected with ARVC compared to non-affected normal Boxers and non-Boxer control dogs. Signal averaged ECG (SAECG) was also performed in all dogs, and troponin I concentrations were measured. Dogs were classified into five groups using Holter monitors and measurement of frequency of ventricular arrhythmia (VPCs/hr). Seventy dogs in total were evaluated for the study, with 15 Boxer dogs in group 1 (> 1000 VPCs/24 hrs), 10 Boxer dogs in group 2 (200-999 VPCs/24 hrs), 15 Boxer dogs in group 3 (25-199 VPCs/24 hrs), 15 Boxer dogs in group 4 (< 24 VPCs/24 hrs) and 15 non-Boxer control dogs in group 5 (< 24 VPCs/24 hrs). Two-dimensional echocardiography, TDI, SAECG and troponin I concentrations were measured in all dogs. When comparing all groups, there were no significant differences in the TDI parameters measured between groups. This finding suggests that ventricular dysfunction may be uncommon in affected Boxer dogs. Furthermore, no significant correlations between TDI and SAECG variables were found. Significant differences in troponin I concentrations were found between groups of dogs, namely Boxers and the non-Boxer control dogs. However, a correlation between VPCs/hr and troponin I concentration was not found. ACKNOWLEDGEMENTS I would like to extend my sincere appreciation and thanks to several key individuals who provided so much of their time, effort, advice and support to complete this project. First and foremost, I would like to thank my amazing mentor Dr. Lynne O'Sullivan who has always believed in my abilities even when I doubted them. Without her guidance, encouragement and support, I would not be where or who I am today. She has been a true role model for me, and I feel truly fortunate that I was given the opportunity to learn under her wonderful guidance. Dr. Michael O'Grady also deserves similar praise as a wonderful co-mentor during my D.V.Sc and during the completion of this project. I truly feel that I had the two best cardiology mentors on the planet (or as I called them, my "cardiology mom and dad"), and it has been such a sincere pleasure to work and learn with both of them. I would also like to sincerely thank my other Graduate Advisory Committee members - Drs. Sandra Minors and Robert Hamilton. Their continuous feedback and advice has been instrumental in completing this project to date. I would like to thank one of the largest driving forces of this project who worked so hard behind the scenes initially, and was "my right hand woman" so to speak during the data collection portion of the project - Cindy Walker. Her sincere dedication to this project was awe-inspiring, and she was absolutely instrumental in the recruitment of the majority of the Boxers for this project, as well providing technical support for me, especially with the analysis of thousands upon thousands of hours of Holter recordings. Her positive attitude and personality made working i with her a pleasure and allowed the project to run so smoothly, and I can never thank her enough for all of her help both personally and professionally. I thank Jim Mcintosh, technologist at the Guelph General Hospital, for performing the troponin analysis for this project. I also thank Dr. Jeff Caswell in the Department of Pathobiology for generously donating several histopathology images to include in this manuscript. I especially thank William Spears in the Department of Population Medicine for his wonderful statistical expertise. I also thank our other members of the wonderful cardiology team at the Ontario Veterinary College, including Drs. Kimberly Hawkes and Maggie Schuckman, as well as Deborah Kingston for their constant support, laughter, and friendship. I feel honoured to have worked with such a wonderful group of people during my D.V.Sc. and it would be difficult to put into words what their friendship has meant to me. I thank the supreme generosity of the wonderful Pet Trust of the Ontario Veterinary College program who provided the financial support of this project - without their support this project would not have been possible. Finally, I would like to thank all those people of the Ontario Veterinary College - fellow D.V.Sc. students, as well as the technical, administrative and front desk staff who provided much needed support to complete this project. I also thank my amazing family and friends who I am sure are now well educated about the ins and outs of arrhythmogenic right ventricular cardiomyopathy [whether they liked it or not!). And most importantly, all the wonderful Boxers, breeders and lovers of Boxers who cared enough about the well being of this wonderful breed to support the completion of this project. DECLARATION OF WORK PERFORMED I declare that, with the exception of the items below, all work reported in this thesis was performed by the author. Telephone interviews for owners of Boxers interested in study participation were performed by Cindy Walker. Assistance in the analysis of the Holter recordings was also performed by Cindy Walker. Laboratory support was provided by the Animal Health Laboratory at the University of Guelph as well as Guelph General Hospital (serum troponin I concentrations). All statistical analysis was directed by William Sears. IV TABLE OF CONTENTS PAGE ACKNOWLEDGEMENTS i DECLARATION OF WORK PERFORMED iv TABLE OF CONTENTS v LIST OF TABLES viii LIST OF FIGURES ix LIST OF ABBREVIATIONS USED x CHAPTER 1 - LITERATURE REVIEW 1.0 Arrhythmogenic Right Ventricular cardiomyopathy in Humans 1 1.0.1 Definitions and Classification 1 1.0.2 Natural History of Disease 2 1.0.3 Prevalence of Disease 3 1.0.4 Pathological Changes Associated with ARVC 4 1.0.5 Etiology of ARVC 6 1.0.5.1 The Adhesion of cardiomyocytes: The Intercalated Disk 8 1.0.5.2 The Cell Adhesion Theory for ARVC: A Disease of the Desmosome 10 1.0.6 The Genetics of ARVC 13 1.0.7 Clinical Signs of ARVC 15 1.0.8 Etiology of Ventricular Arrhythmia in ARVC 16 1.0.9
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