The Nuts and Bolts of Cardiac Resynchronization Therapy

221 Pages·2007·3.701 MB·English

The Nuts and
Bolts of
Cardiac
Resynchronization
Therapy
Tom Kenny
Vice President Clinical Education & Training
St Jude Medical, Austin, Texas
© 2007 St Jude Medical
Published by Blackwell Publishing
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First published 2007
1 2007
ISBN: 978-1-4051-5372-0
Library of Congress Cataloging-in-Publication Data
Kenny, Tom, 1954-
The nuts and bolts of cardiac resynchronization therapy / Tom Kenny.
p. ; cm.
Includes bibliographical references and index.
ISBN 978-1-4051-5372-0 (alk. paper)
1. Heart failure--Treatment. 2. Cardiac pacing. I. Title.
[DNLM: 1. Heart Failure, Congestive--therapy. 2. Cardiac Pacing,
Artifi cial. 3. Defi brillators, Implantable. 4. Pacemaker, Artifi cial.
WG 370 K36n 2007]
RC685.C53K46 2007
616.1’23025--dc22
2006035499
A catalogue record for this title is available from the British Library
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Contents
Preface, v 14 Basic ECG Interpretation for CRT Systems, 93
1 Understanding Heart Failure, 1 15 CRT System Optimization, 103
2 Cardiovascular Anatomy of the Healthy 16 Troubleshooting the Non-Responder, 109
Heart, 6
17 Defi brillation Basics, 116
3 Cardiac Physiology and Heart Failure, 11
18 Advanced Defi brillation Functions, 125
4 Causes of Heart Failure, 17
19 Advanced CRT ECG Analysis, 135
5 The Neurohormonal Model of Heart
20 DFT Management in CRT-D Patients, 144
Failure, 23
21 Atrial Fibrillation, 150
6 An Overview of Heart Failure Drugs, 27
22 CRT in Post-AV Nodal Ablation Patients, 158
7 Ventricular Dyssynchrony, 34
23 Special CRT Device Features, 163
8 Arrhythmias in Heart Failure Patients, 38
24 Diagnostics, 169
9 Indications for CRT, 54
25 A Systematic Guide to CRT Follow-Up, 177
10 Types of CRT Systems, 64
26 Troubleshooting, 186
11 Implant Procedures, 72
Glossary, 191
12 Basic Programming, 79
Index, 213
13 Advanced Programming, 87
iii
Preface
A lot has happened since the day I was involved in cal application of these devices, writing about CRT
caring for my fi rst patient with an implanted car- is a little like writing about the future.
diac rhythm management device. Back then, about There are aspects to these devices that we still do
the only devices available were fairly simple VVI not understand. Algorithms and features are still
pacemakers – at least, they look simple today. Back evolving. In fact, even a few years from now, this
then, we thought adjustable programmable rates book may seem out of date. Manufacturers have
and output inhibition were very sophisticated con- evidenced a strong commitment to put the most
cepts. I can remember how incredible the fi rst dual- advanced and useful tools into the hands of clini-
chamber pacemakers seemed, and can still recall cians. That means a steady stream of new products
learning about AV delays and other dual-chamber and features!
timing cycles. My main concern is that clinicians from all types
When implantable defi brillators were intro- of practices understand the basics – the nuts and
duced, they were just that: implantable defi brilla- bolts – of these CRT devices. It is hard to imagine
tors. Some of those fi rst patients who needed both any sort of clinical practice that will not encounter
pacing and defi brillation ended up with two devic- CRT systems sooner or later. But while these sys-
es! Today, you cannot fi nd an implanted defi bril- tems may be new and even a bit complicated, they
lator on the market without very advanced pacing work on some fundamental concepts that clini-
functionality. cians can readily understand. It is my goal to try to
The cardiac resynchronization therapy (CRT) make these concepts and the device functions that
system is a device I would never have foreseen back address them as simple and understandable as pos-
in my rookie year as a clinician. Comparing those sible.
simple single-chamber pacemakers I worked with This book could not have been written without
then with today’s CRT devices is like comparing a the outstanding contributions of many of my col-
wagon with a space ship. leagues. I want to particularly recognize the work
This is by far the longest and most complex book of Dr Angelo Carboni of the University of Parma,
I have ever written. Spurred by the success of The Italy, for his pioneering educational efforts in CRT
Nuts & Bolts of Cardiac Pacing and The Nuts & Bolts training. I would also like to thank Dr. Mark Kroll
of ICD Therapy, I wanted to tackle the latest type for his insights into the nature of defi brillation. In
of device that is turning up in clinics around the my own offi ce, I must thank David Andreasen for
world. The CRT device is the most promising, most assisting me in a review of the manuscript. I am also
powerful and most complicated implantable car- grateful to the ‘behind-the-scenes’ team of Jo Ann
diac device available today. LeQuang, who helped prepare the manuscript, Be-
For that reason, I want to go on the record by linda Kinkade who handled the art work, and my
saying that this book was written at the advent of gracious editor, Fiona Pattison.
CRT devices. Unlike my books on pacing and ICDs, Of course, the biggest debt of gratitude I owe is
which were written after decades of successful clini- to my family, all of whom have more or less come
v
vi Preface
to terms with having an author in the family. They and opinions, and I appreciate the tremendous
have generously given me time to devote to my new support and confi dence that readers have shown
passion of writing and have been my best critics me.
and strongest allies.
Tom Kenny
It is my sincere hope that you fi nd this book of
October, 2006
immediate practical use. I welcome your comments
Austin, Texas
The Nuts and Bolts of Cardiac Resynchronization Therapy
Tom Kenny
Copyright © 2007 St Jude Medical
1
Chapter 1
Understanding Heart Failure
Although heart failure (HF) was observed in ancient curred was similar to waiting for metastasis rather
times (ancient physicians called it ‘dropsy’), medical than screening for a primary tumor.2
science has been slow to respond to its challenge. The American College of Cardiology and Ameri-
Unlike other things that concern cardiologists, HF can Heart Association defi ne heart failure as ‘a
is a syndrome rather than a disease, i.e. it is a constel- complex clinical syndrome that can result from
lation of symptoms. There remains no straightfor- any structural or functional cardiac disorder that
ward way to diagnose the disease; classifi cation sys- impairs the ability of the ventricle to fi ll with or
tems are more subjective than objective and we are eject blood’.3 There is no objective defi nition of HF
only recently beginning really to understand what because there are no currently agreed-upon cut-
goes on when the human heart begins to fail. off values in terms of cardiac dysfunction, such as
The name of the syndrome itself is something change in fl ow, pressure, dimension or volume. The
of a misnomer. The heart does not ‘fail’ in a sud- main symptoms are shortness of breath and fatigue,
den spasm. The failure is a gradual, stepwise degen- which often manifests as exercise intolerance. Fluid
eration. Not too many years ago, all we clinicians retention may be observed and, even if present, may
could do in the face of progressive HF was keep the not dominate the clinical presentation. A straight-
patient comfortable in the face of the inevitable forward diagnosis is not possible and, when diag-
decline. Even today, the prognosis for HF patients nosed, HF should not be the sole fi nding.
is not good. However, new treatment options are HF impairs the heart’s ability to pump blood and
changing how we think about HF and that includes that, in turn, causes an inadequate blood supply to
not just trying to stop the progressive deterioration the body’s main organs. This lack of oxygen-rich
but actually to fi ght to reverse it. As clinicians, we blood fl ow to the brain, liver and kidneys is respon-
are not always successful in the fi ght against HF, but sible for some of the symptoms of HF. As the heart’s
every year we become better and better equipped. pump becomes less effective, blood can pool in the
In fact, Dr John G. F. Cleland stated recently in an heart and stagnate. It can back up into the veins
interview that at this point in medical history, ‘I or clots may form, increasing the patient’s risk of
think it’s realistic to talk in terms of remission of stroke. The symptoms relate to an inadequate oxy-
heart failure’.1 genated blood supply to the body, including:
Most clinicians have heard the term congestive • Dyspnea (shortness of breath)
heart failure (CHF). Although you still hear it, it is • Fatigue, feeling overtired
starting to sound old-fashioned. Congestion is a • Edema or fl uid accumulation.
troublesome and extremely obvious symptom of
advanced HF. Today we know that patients can have
Types of heart failure
HF without congestion. In fact, by the time fl uids
start to accumulate, the heart has withstood con- Since the defi nition of HF is vast, it is not unusual
siderable assault. Early treatment of HF involves for clinicians to describe HF further to help describe
diagnosing and managing the syndrome long be- the type and stage of the condition. Some of the ad-
fore fl uid overload becomes a problem. In fact, Dr. jectives used with HF include: chronic, acute, con-
Jonathan Sackner-Bernstein wrote that not treating gestive, decompensated, systolic, diastolic, right-
a heart failure patient until fl uid accumulation oc- sided and left-sided.
1
2 The Nuts and Bolts of Cardiac Resynchronization Therapy
Acute heart failure (AHF) is used to describe two paired right-ventricular pumping action, causing
different things. Sometimes the term is heard for congestion in systemic circulation. Left-sided HF
new-onset cases of HF. However, the term is often is by far the more common type, although cases of
applied when a patient with heart failure experienc- ‘true right-sided HF’ have been documented. Over
es a sudden and dangerous worsening of symptoms, the long term, patients may develop both forms of
typically characterized by pulmonary or peripheral HF, in that left-ventricular dysfunction eventually
congestion (or both). Patients with chronic heart causes right-sided failure.
failure may have bouts of AHF, sometimes requir-
ing emergency hospitalization.
Classifi cation of HF
Decompensation is a term that means ‘failure to
compensate’. It describes quite well what happens as When classifying heart failure, the most commonly
heart failure progresses. In the early stages of HF, the used method is not necessarily the most elegant. The
heart develops some radical methods to compen- New York Heart Association (NYHA) came up with
sate for its failings and still provide the body with an a four-level classifi cation scale which is still in broad
adequate supply of oxygenated blood. As the heart use around the world today.4 Although subjective
continues to fail, the heart loses its ability to com- and based on symptoms, the NYHA scale has prov-
pensate and starts to pump inadequately. Decom- en to be exceedingly useful in helping to quantify a
pensated HF is an advanced form of HF. syndrome that seems to defy hard defi nitions. The
Chronic HF (which confusingly sometimes uses NYHA scale maps the degree of exertion required to
the same acronym as congestive heart failure or elicit symptoms (see Table 1.1).
CHF) describes most of what we clinicians know as The American College of Cardiology (ACC) and
HF. Not long ago, it was common to talk about pa- American Heart Association (AHA) proposed an
tients being ‘in heart failure’ or ‘out of heart failure’ alternative classifi cation system for HF which is
as if HF was something that might clear up. While not in widespread use despite its obvious clinical
symptoms can be alleviated, today we recognize that value. This system allows for the classifi cation of the
HF is a chronic condition. asymptomatic and mildly symptomatic patient as
Systolic and diastolic HF will be discussed in more well as those with more advanced cases of HF with-
detail in a later chapter, but they refer to the portion out relying on exertion to provoke symptoms. One
of the cardiac cycle where the heart can no longer reason for this new classifi cation system is that we
pump effectively. Systolic HF may be thought of as truly do not understand why exercise should pro-
the inability to eject blood effectively during the car- voke symptoms. For instance, it has been observed
diac cycle (aligning with systole), while diastolic HF that some patients with markedly impaired left-
generally refers to the heart’s inability to fi ll effective- ventricular function may be asymptomatic during
ly with blood prior to pumping (matching diastole). exercise. Other patients may have symptoms with
While these terms and conditions are important to exercise because of mitral valve regurgitation, pul-
know, systolic and diastolic HF are not mutually ex- monary disease or general poor condition. Thus,
clusive. Many patients have both together and, over the presence of dyspnea with exercise is not neces-
the long term, it is diffi cult to imagine a patient with sarily a reliable yardstick.
systolic HF who does not have impaired diastolic The ACC and AHA have proposed another clas-
function and vice versa. Thus, when the adjectives sifi cation system3 (see Table 1.2) which offers the
‘systolic’ or ‘diastolic’ appear together with HF, they
tend to describe what is more dominant and observ-
able in the patient at that particular point in time. Table 1.1 New York Heart Association classifi cation system
Left-sided and right-sided HF are sometimes
NYHA class Effort required to elicit symptoms
used, but these terms do not indicate which ven-
tricle is the more damaged. Left-sided HF does in-
I Exertion that would limit normal individuals
deed refer to the left ventricle’s ineffective pump- II Ordinary exertion
ing action of blood and manifests as congestion in III Less than ordinary exertion
the pulmonary veins. Right-sided HF involves im- IV Rest
CHAPTER 1 Understanding Heart Failure 3
Table 1.2 American College of Cardiology (ACC)/American 1970 to 400 000 annually in 1990.5 The AHA says
Heart Association (AHA) classifi cation the number in the year 2000 is 550 000 new cases
a year.6 HF is one of the few forms of heart disease
ACC/AHA Defi nition
actually increasing in incidence. In the population
class
of Americans < 75 years old, men are more likely to
A Patients at high risk of developing left- develop HF than women. At age ≥ 75 years, the inci-
ventricular (LV) dysfunction dence becomes more balanced between the genders.
B Patients with LV dysfunction who have not Hospital discharges (patients alive or dead at time
developed symptoms
of discharge) show that heart failure is increasing
C Patients with LV dysfunction with current or
over time, more than doubling from 1980 to 2003
prior symptoms
D Patients with refractory end-stage HF (see Fig. 1.1).
Prevalence is another public health term used to
describe the number of people who have a condi-
advantage of including asymptomatic (actually, it tion at any given time. HF is increasing in preva-
would be more accurate to say pre-symptomatic) lence mainly because the population, overall, is
patients without neglecting the progressive nature aging and HF is a chronic condition. Of people
of the condition. above the age of 65, about 6–10% have some form
While the presence of left-ventricular (LV) dys- of HF7 (see Fig. 1.2). As better medical treatment
function is common in HF patients and is the basis allows people to live longer and as we know how to
of the ACC/AHA classifi cation scale, the presence manage HF better, the prevalence of the syndrome
of LV dysfunction does not defi ne HF, nor does its will continue to increase. While the incidence of HF
absence preclude it. is higher among men (at least up until age 75), the
prevalence statistics show that in the USA, more fe-
males have HF than males. That is partly due to the
Incidence, prevalence, populations
fact that women live longer and that many women
Incidence is a public health term used to defi ne have a less severe form of HF known as diastolic
the number of new cases of a disease each year in dysfunction.
a particular population. The incidence of HF has HF contributes to more than 287 000 deaths an-
been growing steadily from 250 000 annually in nually. The real extent of the devastation caused by
Hospital Discharges for Heart Failure by Sex
700 (United States: 1979-2003)
ds 600
n
a
us 500
o
h
n T 400
es i 300
g
har 200
c
s
Di 100
0
79 80 85 90 95 00 03
Ages
Male Note: Hospital discharges include people discharged alive and dead.
Female Source: National Hospital Discharge Survey, CDC/NCHS and NHLBI.
Figure 1.1 Hospital discharge rates for heart failure. The number of discharges of people from US hospitals with the
diagnosis of heart failure has increased steadily since 1979. The gap between male and female patients has widened over
time.
4 The Nuts and Bolts of Cardiac Resynchronization Therapy
Prevalence of Heart Failure by Age and Sex 10.9
11
(NHANES: 1999-2002)
9.8
9
n
o
ati 7 5.8 6.2
ul
p
o
P 5
of 4.1
Percent 3 1.8 1.5 2.3
1 0.3 0.3 0.5 0.4
-1
20-34 35-44 45-54 55-64 65-74 75+
Ages
Male
Source: CDC/NCHS and NHLBI.
Female
Figure 1.2 Heart failure prevalence by age and sex. The prevalence of heart failure increases sharply with advancing age.
Up to age 74, more men than women have heart failure. This reverses at ages above 75, when slightly more females have
heart failure than males. Women tend to develop heart failure later in life and to live longer than men.
HF is probably better captured in what it costs so-
References
ciety. HF costs the world about $60 billion a year
and accounts for 12–15 million offi ce visits and 6.5 1 Stiles S. CARE-HF: CRT improves survival, symptoms
million hospital days.8 In the USA, HF is the single and remodeling—and sometimes achieves HF “remis-
most common Medicare diagnosis-related group sion”. Available at http://theheart.org/printArticle.
(DRG) and Medicare spends more on HF than on do?primaryKey=399895. Accessed March 22, 2005.
any other disease.9 2 Sackner-Bernstein J. Heart failure treatment options.
In: Resynchronization and Defi brillation for Heart Fail-
HF is a progressive disorder that can affect more
ure: A Practical Approach. Hayes DL, Wang PJ, Sackner-
than just the heart: it often affects the lungs, liver
Bernstein J, Asirvatham SJ, eds. Oxford, UK: Blackwell
and kidneys. As a patient’s functional status deterio-
Futura (Blackwell Publishing) 2004:2.
rates, his or her chance of survival decreases. In the
3 Hunt SJ, Baker DW, Chin MH et al. ACC/AHA Guide-
earlier stages of the disease, HF is associated with a lines for the evaluation and management of chronic
higher incidence of sudden cardiac death, while in heart failure in the adult: executive summary. Circula-
later stages, worsening HF is more likely to be the tion 2001; 104:2996–3007.
cause of death. The main objective in treating HF 4 The Criteria Committee of the New York Heart Asso-
patients has been to improve symptoms, reduce the ciation. Diseases of the Heart and Blood Vessels: No-
risk of death and disease progression and enhance menclature and Criteria for Diagnosis, 6th edn. Boston,
MA: Little Brown 1964.
the patient’s quality of life.
5 Jaski BE. Basics of Heart Failure: A Problem-Solving
One of the latest innovations for HF treatment
Approach. Norwell, MA: Kluwer Academic Publishers
is cardiac resynchronization therapy, which is a de-
2000.
vice-based treatment. However, HF requires a mul-
6 American Heart Association. 2002 Heart and Stroke
tidisciplinary approach and rarely is any HF patient
Statistical Update. Dallas, TX: American Heart Associa-
well served by one drug or even one therapeutic tion 2001.
approach. It is a complex syndrome which requires 7 ACC/AHA Guidelines for the Evaluation and Manage-
careful management. ment of Heart Failure, October 24, 2002.
CHAPTER 1 Understanding Heart Failure 5
8 Zevitz ME. Heart Failure. Available at http://www. 9 Weintraub NL, Chaitman BR. Newer concepts in the
emedicine.com/med/topic3552.htm. Accessed April 23, medical management of patients with congestive heart
2003. failure. Clin Cardiol 1993; 16:380–390.
The nuts and bolts of understanding heart failure
• Heart failure (HF) is not a disease with a specifi c classifi cation system, it is not as widely used as
diagnostic test. It is a complex syndrome of the NYHA classes.
symptoms and conditions. • In populations < 75 years old, more men
• HF is increasing in incidence and prevalence. In than women get HF every year (incidence).
the USA, Medicare spends more on HF than on At ≥ 76 years old, the incidence is about equal
any other condition. Worldwide, HF costs about for men and women. However, more women
$60 billion annually. than men have HF at any given point in time
• While there are many ‘types’ of HF, the main (prevalence), partly because women live longer
one of concern for device-based therapy is and partly because they are more likely to have
chronic HF. It may or may not be accompanied less severe diastolic forms of HF.
by signifi cant congestion. • The hallmark symptoms of HF include
• HF affects the heart’s ability to pump blood shortness of breath, fatigue and fl uid
effectively. It can be systolic (impairs ability to accumulation. Exercise intolerance is frequently
pump blood out) or diastolic (impairs ability of the way patients are classifi ed (the NYHA
heart to fi ll with blood). Having one form of HF classifi cation system is based on symptoms that
does not preclude the other. Some patients have occur based on levels of exertion). While left-
both systolic and diastolic HF. ventricular (LV) dysfunction and congestion are
• The most commonly used system to rank HF common in HF patients, neither one defi nes HF.
patients is the New York Heart Association In fact, many people with HF may have neither
(NYHA) classifi cation, where Class I is the LV dysfunction nor congestion.
least symptomatic and Class IV is the most • On the other hand, LV dysfunction cannot
symptomatic. These classes are not static and are occur without some degree of HF being present,
based on somewhat subjective criteria. even if the patient is not (yet) symptomatic.
• The American College of Cardiology (ACC)/ • The best way to think of HF is as a deterioration
American Heart Association (AHA) have of the heart’s ability to pump blood effectively.
proposed an alternative classifi cation system of • Many other organs can be affected by HF
four stages, A–D, where A indicates patients at besides the heart, mainly the lungs, liver and
high risk of developing HF and Class D end- kidneys.
stage refractory HF patients. The ACC/AHA • HF is associated with many other conditions
scale is based on degree of left-ventricular (co-morbidities), including diabetes,
dysfunction. Although this is an important hypertension and atrial fi brillation.