2.3 Cardiac Arrhythmia - QSpace - Queen's University

114 Pages·2010·5.29 MB·English

by  Geoffrey Seaborn

CHANGES IN AUTONOMIC TONE RESULTING FROM CIRCUMFERENTIAL
PULMONARY VEIN ISOLATION
by
GEOFFREY SEABORN
A thesis submitted to the
School of Computing
In conformity with the requirements for
the degree of Master of Science
Queen’s University
Kingston, Ontario, Canada
December 2010
Copyright ©, Geoffrey Seaborn, 2010
Abstract
In patients with normal hearts, increased vagal tone is associated with the onset of paroxysmal
atrial fibrillation (AF). Vagal denervation of the atria renders AF less inducible. Circumferential
pulmonary vein ablation (CPVA), with or without isolation (CPVI), is effective for treating
paroxysmal AF, and has been shown to impact HRV indices, in turn reflecting vagal denervation.
We examined the impact of CPVI on HRV indices over time, and evaluated the
relationship between vagal modification and rate of recurrence of AF. High resolution ECG
recordings were collected from 64 patients (49 male, 15 female, mean age 57.1±9.7) undergoing
CPVI for paroxysmal (n=46) or persistent (n=18) AF. Recordings were made pre-procedure, and
at intervals up to 12 months. Success was defined as no recurrence.
After CPVI, 27 patients presented recurrence. Pre-procedure HRV variables did not differ
from controls in patients with a subsequent successful procedure. However, patients with
recurrence demonstrated significantly-reduced pre-procedure HRV compared both with controls,
and with patients having successful procedures (39.6±23.4 & 33.7±19.2 vs 21.8±11.8, P =0.01 &
P=0.04). Following the procedure, HRV was reduced vs pre-procedure in patients with successful
procedures (33.7±19.2 vs 18.6±15.8, P=0.01), and did not differ from unsuccessful procedures
over a 12 month FU. Both groups were reduced compared with a control value. There was no
i
significant difference in HRV between patients who experienced recurring AF (n=9), and those
who experienced AT or flutter (n=18).
Our data suggests that patients experiencing recurrence after one procedure have reduced
HRV that is not changed by CPVI; whereas patients with a successful single procedure
experience a change in HRV variables that is sustained over a long period, but is no different
post-procedure from patients experiencing recurrence. These data suggest that denervation
associated with CPVI may benefit patients with normal vagal tone prior to the procedure, but that
sustained denervation is not a critical factor in successful outcome after CPVI.

ii
Acknowledgements
I feel very privileged to hold a position at the Queen’s Arrhythmia Research Centre
(ARC), which is a facility that houses interdisciplinary collaboration between students and faculty
from the School of Medicine and the School of Computing, as well as clinicians and staff from
the Kingston General Hospital (KGH). Although the ARC is still in its early days, it is the
foundation of many promising research projects set to improve cardiac care. There are a number
of people whom I would like to acknowledge for supporting my MSc research at the ARC.
I would like to thank my supervisors, Dr. Damian Redfearn and Dr. Selim Akl, for their
expertise, guidance, and constant support, both financially and academically. I received a warm
welcome upon joining the group; I was immediately introduced to many of their colleagues, and
was provided with second homes in the School of Computing, and in the newly-renovated ARC at
KGH. Although Dr. Redfearn has a busy schedule as a clinician and as the director of the EP lab,
as does Dr. Akl as the director of the School of Computing, they always made time to supervise
my work, and to ensure that I was involved in many exciting research projects. Their enthusiasm
toward my work has kept me motivated, and has given me the confidence necessary to publish
my results under challenging deadlines. I am sincerely indebted to my supervisors, as it is thanks
to them that I am able to achieve my goals and contribute to the field to which I have long been
dedicated.
iii
I would like to acknowledge my academic peers, Sunny Gupta, Charlotte Haley, and
Sami Torbey, as well as the research staff, Alecia Jones, Sharlene Hammond, and Johnny Siu.
They have all been very enthusiastic and supportive of my work, and have made significant
contributions to this thesis over the past few months. I am fortunate to have such a positive
working environment, and it is thanks to them that I am able to look forward to arriving here each
morning.
In summary, I feel very fortunate to have been given a position here, as I couldn’t
imagine a way in which the past few months could have been more enjoyable. I am thankful for
having such supportive supervisors, and for having been given this opportunity to work with so
many great people on projects that I truly enjoy. I certainly don’t take it for granted, and continue
to work hard in hopes that my work here will contribute toward improving cardiac care, and also
to bring continued recognition to the ARC as the preferred centre in Canada for research into
cardiac arrhythmia.
iv
Contents
Abstract i
Acknowledgements iii
Contents v
List of Equations vii
List of Figures ix
List of Tables xi
Chapter 1:
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Chapter 2:
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 The Heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
v
2.2 Electrocardiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.3 Cardiac Arrhythmia . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.4 Heart Rate Variability . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Chapter 3:
Vagal Denervation is not a Critical Factor for Successful Outcome after
CPVI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.1 Experimental Background . . . . . . . . . . . . . . . . . . . . . . . . 52
3.2 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.3 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Chapter 4:
Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.1 Discussion of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.2 Study Limitations and Future Work . . . . . . . . . . . . . . . . . . . . 80
Chapter 5:
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Appendix 1: Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
vi
List of Equations
2.1 Formula for Calculating SDNN . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.2 Formula for Calculating RMSSD . . . . . . . . . . . . . . . . . . . . . . . . 37
2.3 Formula for Calculating pNN50. . . . . . . . . . . . . . . . . . . . . . . . . 37
2.4 Formula for Calculating ApEn (part 1). . . . . . . . . . . . . . . . . . . . . . 44
2.5 Formula for Calculating ApEn (part 2). . . . . . . . . . . . . . . . . . . . . . 44
2.6 Formula for Calculating ApEn (part 3) . . . . . . . . . . . . . . . . . . . . . . 44
2.7 Formula for Calculating ApEn (part 4) . . . . . . . . . . . . . . . . . . . . . 44
2.8 Formula for Calculating ApEn (part 5) . . . . . . . . . . . . . . . . . . . . . . 44
2.9 Formula for Calculating SampEn (part 1) . . . . . . . . . . . . . . . . . . . . . 45
2.10 Formula for Calculating SampEn (part 2) . . . . . . . . . . . . . . . . . . . . 45
2.11 Formula for Calculating SampEn (part 3) . . . . . . . . . . . . . . . . . . . . 45
2.12 Formula for Calculating DFA (part 1) . . . . . . . . . . . . . . . . . . . . . . 46
2.13 Formula for Calculating DFA (part 2) . . . . . . . . . . . . . . . . . . . . . . 46
vii
2.14 Formula for Calculating SD1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
2.15 Formula for Calculating SD2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
viii
List of Figures
2.1 Structure of the Heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 Layers of the Heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3 Cardiac Muscle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.4 Electrical System of the Heart . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5 Autonomic Innervation of the Heart . . . . . . . . . . . . . . . . . . . . . . . 16
2.6 Anatomy of the autonomic innervation of the heart . . . . . . . . . . . . . . 18
2.7 Normal Cardiac Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.8 AF vs Normal Sinus Rhythm . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.9 Holter Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.10 Implantable Loop Recorder . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.11 Catheter Ablation of Tissue in the Right Atrium . . . . . . . . . . . . . . . . 30
2.12 Pulmonary Vein Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
ix