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Sudden Transitional Death Risk: When an ICD Isn’t the
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Presenters and Moderator
Presenters:
Tom Deering, M.D
Electrophysiology and Arrhythmia Service, Piedmont Hospital, Atlanta, Georgia,
USA.
Helmut Klein, MD
Director of Cardiology, University of Magdeburg, Magdeburg, Germany
Leonard Ganz, MD
Director of the Electrophysiology Service, University of Pittsburgh, Pittsburgh,
Pennsylvania, USA
Moderator:
Alfred Buxton, MD
Sudden Transitional Death Risk: When an ICD Isn't the Answer (CE for
Nurses)
Course Overview
COURSE INTRODUCTION/METHOD OF PARTICIPATION
To complete this course, you must do the following:
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

Read the Needs Statement/Overview and Course Objectives.
Study the Terminology.
Study the Content Review.
Complete the comprehensive Post Test
To receive 1 hour of Continuing Nursing Education credit for the course,
complete the comprehensive post test and activity evaluation form at the end of
this activity, and follow the instructions to receive your certificate.
NEEDS STATEMENT / OVERVIEW
In this document three noted experts provide a discussion of the risk of sudden
death due to ischemic heart disease and how a wearable cardioverter-
defibrillator vest can fill the gaps in risk, particularly, where an implantable
defibrillator must be delayed or is not indicated.
Key research is reviewed to present the clinical picture, and direct experience
of the use of the wearable vest is presented in several case studies.
INTENDED AUDIENCE
Physicians, nurses, paramedics, emergency medical technicians (EMT) and
other healthcare professionals who may treat patients presenting with acute MI.
PURPOSE AND OVERALL GOAL
This program introduces healthcare professionals to the use of the wearable
cardioverter-defibrillator vest to fill gaps of high risk in which an implantable
device is not indicated.
OBJECTIVES
This booklet is a collection of transcripts from multiple presenters at the CME
lecture entitled, "Sudden Transitional Death Risk: When an ICD isn't the
Answer", presented on November 11, 2006. Objectives for each presentation
are contained within their respective sections of the booklet.
FACULTY DISCLOSURE STATEMENT
The authors/presenters of the sections contained herein have indicated that
they have no financial arrangements or affiliations with any of the corporate
organizations offering financial support or educational grants for this activity,
with the exception of Dr. Tom Deering, who has received research grants, as
has his institution, because of research done in association with Lifecor.
Sudden Transitional Death Risk: When an ICD Isn't the Answer (CE for
Nurses)
Terminology
ACE inhibitor (angiotensin-converting enzyme inhibitor): a class of drugs
used in the treatment of hypertension and heart failure.
Arrhythmogenic RV dysplasia: a right ventricular abnormality producing
arrhythmia.
Beta blocker: a class of drugs used to slow the heartbeat and treat
hypertension.
Brugada Syndrome: severe disturbances of the rhythm of the heart that can
cause death.
Cardiomyopathy: Primary myocardial disease, often of obscure or unknown
etiology.
Ejection fraction: A measure of ventricular contractility.
Hypertrophic cardiomyopathy: A congenital heart disease that results in
abnormal thickening of the ventricular septum and left ventricular wall.
ICD: Implantable cardiac defibrillator.
Revascularization: opening of the coronary arteries to blood flow.
Stent: a small expandable mesh implant that holds open a coronary artery.
Ventricular fibrillation (VF): A disorganised chaotic contraction of the ventricle
that fails to effectively pump blood from the ventricle.
Ventricular tachycardia (VT): Abnormal accelerated ventricular rhythm with a
usual rate above 150 beats per minute.
Sudden Transitional Death Risk: When an ICD Isn't the Answer (CE for
Nurses)
Section 1: Filling The Gaps In Our
Utilization Of Defibrillators
By Tom Deering, M.D.
Electrophysiology and Arrhythmia Service,
Piedmont Hospital,
Atlanta, Georgia, USA
INTRODUCTION
This is a discussion about mortality issues and particularly sudden death, and
what the role of the wearable defibrillator might be in preventing sudden death
where gaps in utilization exist.
PURPOSE AND OVERALL GOAL
The purpose of this section is to offer data and experience on how the wearable
defibrillator can fill gaps in utilization for patients subject to sudden death
because of ischemic heart disease.
OVERVIEW
This section provides information on sudden cardiac death, government
guidelines on implantable defibrillators and how the wearable defibrillator can
bridge the gaps of utilization for some high risk groups. The material is
organized around the following categories:
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


Introduction
Sudden Cardiac Death
The Role for the Wearable Defibrillator
High and Low Risk Groups

Conclusion
SECTION OBJECTIVES
After completing this section of the activity the learner should be able to:
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

Describe high and low risk groups for sudden ischemic death
Describe government guidelines for implantable defibrillators
Identify how the wearable defibrillator can bridge any gaps in risk
Sudden Transitional Death Risk: When an ICD Isn't the Answer (CE for
Nurses)
Introduction
This is a discussion about mortality issues and particularly sudden death, and
what the role of the wearable defibrillator might be in this particular subject.
First, it is important to put into perspective the importance of sudden mortality
caused by cardiovascular events. We will then review the role of the ICD and
the guidelines for its use. This will point out where gaps in utilization may exist,
and suggest a potential role for the wearable defibrillator.
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Figure 1: U.S. Mortality
Cardiovascular events and sudden death mortality are the leading cause of
death in the United States, as you can see in Figure 1, and in Western Europe
as well.
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Figure 2: Leading Causes of Death in the U.S
Sudden Cardiac Death
Fortunately, a close look at the management of cardiovascular mortality and
sudden death shows that there are many steps that can be taken to improve
the rates. In addition to general cardiac mortality, there is sudden death,
indicated by the red in the Figure.
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Figure 3: Cardiac vs. Other Causes
In fact, see Figure 3, you have to add up all non-cancer causes of death plus all
cancer causes-- basically all other forms of death--in order to equal that of
sudden cardiac death. So, it is a major public health issue.
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Figure 4: Arrhythmic Causes
In the vast majority of studies, most sudden deaths are arrhythmic in origin, see
Figure 4. This public dilemma offers an opportunity. We need to look at general
medical interventions taken against cardiac problems and then the role of the
ICD so we can see where this opportunity lies. A tiny percentage of the
population is born with good genes and can live to be 100 and never take a
medication. Fortunately, for the rest of the population, there are medicines to
control blood pressure, to control cholesterol, and to treat other disorders.
Even with all our medical interventions, there will still be sudden cardiovascular
incidents, and for that we have the defibrillator--wearable, implantable, or
external and hanging on the wall.
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Figure 5: Sudden Cardiac Death
To review the initial studies using one of the old Myerburg slides, Figure 5,
depicting the risk of sudden death in individual populations, the bigger risks are
shown in the blue, that is, those who have survived an arrest and are prone to
another, and in the green, those who have other high risk factors. The highest
risk is for those with LV dysfunction and with a prior coronary event. Those
high-risk populations are, of course the ones who were used for the initial
studies of implantable defibrillators.
Medical Interventions
We also need to control the risk--with hypertensive medicines, cholesterol
medicines, and other factors--using ACE inhibitors and beta-blockers.
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Figure 6: Primary Prevention Trials
If you look at the TRACE and HOPE trials, Figure 6--those that used ACE
inhibitors, and beta blockers--and you look at the incidence of sudden death, it
has been reduced in these trials, Figure 7 below.
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Figure 7: SCD Reduction
However, if you look at the red, you can see the total mortality and then
compare to the blue, the sudden death mortality. You can see that about 50%
of the total deaths are still sudden in origin. We may have brought down the
overall mortality but there are still a large number of people dying suddenly.
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Figure 8: Secondary Prevention Trials
The Role of the Defibrillator
We need to develop ways to deal with sudden death mortality. That's where the
role of the defibrillator has grown significantly. There are both secondary and
primary prevention trials. In the secondary trials, the patient has already
survived one incident. If you look at the three major trials, see Figure 8, you can
see that there's been an overall reduction in the mortality rate and an overall
reduction in death from arrhythmia, utilizing the defibrillator on an implantable
basis.
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Figure 9: Primary Trials: Mortality
The primary prevention trials have shown similar findings, see Figure 9.
Conventional therapy is shown in the red, and trials with an implantable
defibrillator in the blue. You see on the left the four major trials showing
significant benefit: the significant p values, larger numbers of patients and the
time of follow-up. On the right, you can see in the lighter colors, studies that did
not show a significant benefit and these need to be discussed later.
A number of ICDs are being implanted today, but more needs to be done.
Government agencies, plus doctors of all specialties--primary care, cardiology,
interventional, EP--in conjunction with the manufacturers--need to work
together to promote the use of ICDs.
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Figure 10: Guidelines
Government Guidelines
What are the current ICD guidelines? Multiple guidelines have been issued
over the years, but there is the most recent update, Figure 10. To simplify the
guideline, for primary and secondary prophylactic therapy--ischemic and nonischemic patients are included--the patient should be on optimal medical
therapy to lower the risk.
The guidelines for secondary prophylaxis are straightforward: the patient needs
to have suffered an event and survived. For primary prophylaxis it is a little
more complex. The patient needs a low ejection fraction, II or III class heart
failure, and for ischemics, no revascularization within three months or MI within
40 days. For non-ischemics, the patient also needs a time frame of rest, so the
physician can see how responsive the myocardium will be to therapy and see if
the situation will resolve.
Collection of this data has been mandated by congress and is evaluated and
watched in a registry so that over time more will be known.
Role For The Wearable Defibrillator
This brings us to the main topic: the transitional risk. Is there a role for the
wearable defibrillator? Though the data are not clear yet, it appears there are
five potential areas where there may be benefit. The guidelines are not
perfectly clear on who should be given an implantable defibrillator. There is a
gap between those who fall within these guidelines, and those who might
benefit from a defibrillator but are not covered by the guidelines. The wearable
defibrillator can bridge this gap for some high-risk patients.
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Figure 11: The Wearable Defibrillator
LV Dysfunction
First there are those who have LV dysfunction from an ischemic basis.
Medicare requires 40 days post-infarction or three months postrevascularization. That is probably appropriate because in some patients you
will have remodeling.
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Figure 12: CABG Patch Trial
If we look at some of the older trials, such as the CABG-Patch trial, see Figure
12, there was no difference in survival after revascularization.
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Figure 13: MADIT II Trial
Interestingly, if you look at the MADIT trial, Figure 13, and you look at the timedependence of risk based on revascularization--putting in a defibrillator within
six months of revascularization--you can see that the defibrillator (shown in the
blue) did not have a better survival rate. They were about equal. It didn't prove
beneficial early on after revascularization.
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Figure 14: DINAMIT Trial
Similarly, in the DINAMIT trial, Figure 14, there's no difference. There may have
been an arrhythmic difference, but the overall mortality rates were no better.
You can also look further at the non-ischemic cardiomyopathies. And if you
have someone with a newly diagnosed myopathy, sometimes they progress
and it doesn't resolve--sometimes they stay ill, and sometimes they get better.
We need to treat them and study their progress over time.
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Figure 15: DEFNIITE Trial
If you look at the DEFINITE trial, Figure 15, which studied non-ischemics, and
you look at the two-year mortality rates, there was a tiny improvement with the
defibrillator but it wasn't statistically significant, despite an improvement in
sudden death rates. That study didn't show much benefit.
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Figure 16: SCD-HeFT Mortality
Interestingly, if you look at the SCD-HeFT trial, Figure 16, and you carry it out
to about 18 months, the graphs haven't separated--and this is a large trial with
a mixture of about 50-50 ischemics and non-ischemics.
Early Use
Clearly there are problems with all of these trials: some of them are small,
technology has advanced, and there is no question that we run into statistical
and clinical issues of concern. However, the converse is not true. We have not
proven that putting in an implanted defibrillator is effective early after an infarct,
early after revascularization, or early in the stage of non-ischemic
cardiomyopathy. So this is a gap where the use of a wearable device, for a
short period of time, might be beneficial.
Bridge to Transplant
Another gap zone is the bridge to transplantation. If the transplant is years
away, patient compliance with the inconvenience of the vest may become an
issue. But if it's a question of several months, then certainly the patient can
tolerate wearing the device.
Reversible Cardiomyopathies
Reversible, or possibly reversible cardiomyopathies, are another gap. For
example, someone who has a cardiomyopathy due to hyperthyroidism or a viral
illness. Or, commonly, a tachycardia-mediated cardiomyopathy due to atrial
fibrillation, which may resolve with lowering the heart rate and/or re-establishing
sinus rhythm. It makes little sense to implant a device in a patient who may only
have a transient risk.
Other Ongoing Medical Issues
And then last, the wearable device may be appropriate for those who have
other ongoing medical or cardiovascular issues--for instance, someone who is
in the hospital, has non-sustained VT, has a known cardiomyopathy, but is
being worked up for cancer and may not be a survivor. There is a gap there
where the wearable device might be beneficial.
So there are gaps in the guidelines between where the defibrillator is indicated
and the defibrillator is not indicated, where there may be a role temporarily for a
wearable device to protect these subgroups of patients.
Contraindications
There are some areas, of course, where there is a relative or absolute
contraindication. Someone who has an infected ICD, for example, may not be a
candidate. Or someone who has a big systemic infection, like a bad
pneumonitis, or patients with an external dialysis catheter.
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Figure 17: Sudden Cardiac Death: Epidemiology
Patients with arrhythmic risk
There are also some uncommon cardiomyopathies that are associated with
arrhythmic risk. When we looked at the curves from Myerburg's analyses
earlier, see Figure 17, we focused on those areas that were exceptional.
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Figure 18: Individual Risk
But remember, see Figure 18, the risk in an individual is very low, but the
problem is that that is where most of the cardiovascular event rates and sudden
death occur. So the risk individually is lower, but across the patient population it
may be higher.
Most of these are probably patients who are becoming ischemic, don't have a
lot of risk factors, but are dying suddenly. But there are certain arrhythmic
problems that exist in this group of patients that do pose a risk.
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Figure 19: Miscellaneous Cardiomyopathies
There are also some miscellaneous cardiomyopathies, see Figure 19, like
certain subgroups with a hypertrophic cardiomyopathy, arrhythmogenic RV
dysplasia, certain neuromuscular disorders, or infiltrative cardiomyopathies.
In addition, there are genetic disorders such as the Brugada syndrome, patients
with the long or the short QT syndrome, those with catecholaminergic
polymorphic VT, and those with idiopathic VF. These are patients in whom
there might be arrhythmic risk. Not everybody with a hypertrophic
cardiomyopathy needs a defibrillator, nor does everybody with Brugada's
syndrome. But by the time the general cardiologist or internist sees it,
discusses it with the patient, gets some ancillary studies, or gets it to the EP to
manage it, a significant time lapse can occur. In the patient presenting with
worrisome symptoms of uncommon cardiomyopathies, there may be a role for
the use of the wearable defibrillator. So someone presenting to the physician
with a Brugada EKG might be such a patient.
High And Low Risk Groups
Last are those patients of uncertain benefit. I think what happens is that there
are patients in whom the risk of sudden death is quite low but we're still putting
in implanted defibrillators.
Let's look first at this low risk group. There are a number of well known markers
of arrhythmic risk. And there are markers of autonomic dysfunction like
baroreflex sensitivity and heart rate variability. There are electrophysiologic
markers, like the level of ventricular ectopy, signal-averaged
electrocardiography, inducible VT, T-wave alternans analysis. And then
arrhythmic risk substrate markers, of which the most important marker has
historically been left ventricular systolic dysfunction.
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Figure 20: LVEF Study
If you note this LVEF study, the lower the ejection fraction, the greater the risk
of sudden cardiac death.
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Figure 21: Primary Prevention Trials
Now, Figure 21 is a controversial illustration because a number of disparate
studies have been averaged together. In the red you can see conventional
therapy, and in the blue, defibrillator therapy, and in the green, absolute risk
reduction. But the indication is that there is an absolute risk reduction that
keeps going down because we're expanding the envelope and making
defibrillators more accessible. The people getting defibrillators today
theoretically are at lower risk than the same general population before they
were so readily available.
Within all of these markers we've identified the highest risk group, but I think we
have some people whose risk is now so low compared to, potentially, the longterm risk of the implanted device that we need to re-think the policy.
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Figure 22: TW Alternans Study
Figure 22 shows a study by David Bloomfield this year: ischemic and nonischemic patients with an EF of 25% followed for a little over a year and a half.
Red indicates it's positive or indeterminate and blue that it's negative. And you
can see that if you have a negative T-wave alternans in this study, your risk
was low. More data is needed, clearly, but there is a growing feeling that we
can probably look at people within the high-risk group and identify some who
are actually low-risk and maybe better choose our devices.
Patient Needs
Not everybody who is referred for a defibrillator should get one. Physicians
need to have an honest discussion with their patients, talk about the risk-benefit
ratio. I think in that scenario where you've got a patient who's waiting, there is
role for a wearable device.
High-Risk Groups
Then there are the high-risk groups, patients with multiple co-morbidities or
maybe the elderly.
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Figure 23: MADIT II Trial
The MADIT II trial, Figure 23, compared renal function and mortality: the lower
the glomerular filtration rate, the higher the mortality rate. Conventional therapy
is shown in the blue, ICD in the green, and you can see that in this group with a
GFR less than 35, there was no benefit to having the defibrillator. And that was
a creatinine of 2.4. So there are subgroups that are quite ill with co-morbidities
and may not benefit from a defibrillator. Again, though, there is a potential role
for the wearable defibrillator, while other issues are being discussed and
analyzed.
I think what medicine has done is initially used implantable defibrillators on
patients at very high risk and there were significant benefits, but the benefit to
other patient populations is not as great. Our job as doctors is to balance that
risk-benefit, to know the data, to have open and honest conversations with our
patients. And in the meantime bear in mind that the wearable defibrillator is of
possible benefit in certain high-risk groups.
Conclusion to Section 1
The ICD is a wonderful device, and it saves many live. But there are other
issues of risk to consider. And issues of the patient's individual decision, plus
sometimes scheduling issues.
There is a place for the wearable defibrillator. The conclusions are the
following:
1. Sudden death remains an important clinical issue in the developed
western world.
2. Pharmacologic therapy and ICD therapy have been instrumental in
reducing the rates of sudden cardiac death.
3. The number needed to treat to save a life has decreased with
broadening ICD indications
4. The wearable cardioverter- defibrillator may have a role in managing
the gaps in the post-MI, post-revascularization patient, the person with
a reversible cardiomyopathy, relative contraindications and the
indecisive patient. It also may have a role in the patient who needs
further risk stratification, where the benefit may not be clear, either too
high or too low, or they have an uncommon cardiomyopathy that
requires further evaluation and risk stratification.
It is a complex issue to which there is no absolute answer, but there are gaps
and there are transitional zones where a wearable defibrillator can be of great
benefit.
Section 2: Sudden Arrhythmic Death In
CAD: The Magdeburg Approach
By: Helmut Klein, MD.
Director of Cardiology,
University of Magdeburg
Magdeburg, Germany
INTRODUCTION
This is a discussion about sudden arrhythmic death in coronary artery disease,
and how this is approached in Magdeburg, Germany.
PURPOSE AND OVERALL GOAL
There is sufficient data to conclude that the risk of sudden death is reduced by
an implantable defibrillator.The purpose of this section is to discuss bridging the
transitory risk.
OVERVIEW
This section provides information on the use of the wearable defibrillator in
Magdeburg based around detailed examination of several case studies. The
material is organized around the following categories:





Introduction
The Wearable Defibrillator
Case Studies
The Magdeburg Experience
Conclusion
SECTION OBJECTIVES
After completing this section of the activity the learner should be able to:



Describe the transitory risk to ICD
Discuss several case studies that show a wearable defibrillator helped
bridge a transitory risk.
Describe the overall statistics on the effectiveness of the wearable
defibrillator in Magdeburg
Introduction
This part of the activity will discuss sudden arrhythmic death in coronary artery
disease, and how this is approached in Magdeburg, Germany. There is
sufficient evidence already to conclude that the permanent risk of sudden
death, arrhythmic death, can be effectively reduced by the ICD. The best
approach to bridge the transitory risk of sudden death is still a matter of debate.
Transitory Risk
Transitory risk remains the open question. As discussed above, according to
the specific definition of the DINAMIT trial, the early phase means within the
first 40 days. There's also a transitory risk in the peri-operative phase of the
CABG-Patch, and other cardiac surgery with poor left ventricular ejection
fraction--an ejection fraction of less than 30%.
There are patients waiting for heart transplant who have a low ejection fraction
who certainly have a much higher risk of dying suddenly. These are the major
transitory risk patients, but we also have temporary inability to implant an ICD,
systemic infection and co-morbidity preventing the ICD implant.
Risk Stratification
There is also the problem of risk stratification. There are patients that refuse to
have an ICD implanted for various reasons. The solution for some of these
patients is to have a wearable instead of an implanted device.
In the era of early post-infarct revascularization, the overall mortality and the
incidence of the cardiac arrest in these patients still is very unclear. No study in
this patient population shows what the actual risk of sudden mortality is. Even if
they are successfully revascularized, there are still a number of days of risk if
patients remain with a low ejection fraction. But the number of these patients
who die suddenly is still unknown.
We also do not know what percentage of patients that present with an acute
myocardial infarction, low ejection fraction, will really improve their dysfunction;
specifically patients in the early phase of infarct with an election fraction below
30%. We have seen patients successfully implanted with one or two or more
stents. The vessel is open but the patient still does not recover after the
revascularization and remains at high risk of dying suddenly. Just
revascularizing these patients does not completely remove the risk of death
due to arrhythmia problems.
Bridging Transitional Risk
We need a tool to bridge the transitional risk to ICD--first of all to avoid
unnecessary ICD implants. This has to do with quality of life and it also,
certainly, entails a socioeconomic burden. Risk stratification, so far, has a low
positive predictive accuracy. The ABCD trial may help, but there are only six
centers in Germany-- a country of 82 million people-- where they do T-wave
alternans studies. So risk stratification is still a matter of discussion. And
antiarrhythmic drugs are relatively ineffective and fairly dangerous, specifically
in the early phase of a myocardial infarction.
What are the options to bridge this transitory risk? To remove the risk is very
difficult. Even removing an aneurysm does not necessarily help these patients
significantly. Studies show this does not reduce the risk of death from
arrhythmic causes.
One possibility is the wide distribution of automatic external defibrillators. This
is certainly very helpful in public places and in hospitals. However, 75 to 80% of
the patients having a high risk of dying suddenly will die at home. Even if you
teach the family members to use it and convince them to buy an external
defibrillator, the spouse may well be out shopping when the device is needed.
The Wearable Defibrillator
Another possibility is the wearable defibrillator, Figure 1.
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Figure 1: The Wearable Defibrillator
This is not the very latest model, but it is the one being used in Germany with
patients with ejection fraction of 30% or lower after an acute myocardial
infarction. It includes back electrodes, front electrode, the battery and
electronics, and the response buttons that can be used by the patient.
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Figure 2: Review Apparatus
In Figure 2, you see the battery, the electronic circuits and the telephone
modem which gives the physician the opportunity, via the Internet, to review the
electrocardiograms of these patients once per week.
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Figure 3: Patient wearing Defibrillator
Figure 3 shows a patient wearing the device. It is a device that is easy to put on
and use.
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Figure 4: Training Session
Figure 4 shows a training session. The patients who wear the device require
training, which usually takes about one hour. The technician teaches the patient
how to use the device, how to put it on, to recharge the battery every 24 hours,
how to use the telephone modem, what to do when taking a shower, etc. The
effectiveness of the wearable defibrillator is dependent upon good training, from
the technician or even the physician. There is also a training movie that shows
how to use it.
Training is the key to the success of the wearable defibrillator: so that the
patient is well informed on how to use the device.
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Figure 5: Reviewing the ECG
Equally important, of course, Figure 5, is a doctor's ability, via the Internet, to
look at the electrocardiogram. Either to control the appropriate wearing of the
device or if the patient calls in and has had an alarm or has had a shock. The
doctor can look at the ECG via the Internet to see what occurred.
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Figure 6: Stages of Operation
Operation of the Defibrillator
This chart, Figure 6, shows the stages of operation of the defibrillator. First
there is initial detection of an event and confirmation. Then once the arrhythmia
is identified there's a vibration alarm, there's a low tone warning, and there's a
high volume tone warning. And, finally, if the arrhythmia is still going on, there is
the gel deployment, there is a voice warning to bystanders not to touch the
patient, and there comes the defibrillation shock. Altogether it takes about 30
seconds to deliver the shock.
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Figure 7: The Biphasic Waveform
Initially when the ICD was developed it deployed only a monophasic shock,
Figure 7. But now we have the varying biphasic waveform, according to the
impedance, so the new biphasic waveform is the one that is in the wearable
cardioverter defibrillator available today.
Early Phase Use
Now we will discuss use of the wearable defibrillator in the early phase after
myocardial infarction. Which means that all of the patients that have come to
the hospital and have a STEMI or non-STEMI myocardial infarction, with an
ejection fraction of 30% or lower within the first 72 hours after myocardial
infarction, receive the wearable defibrillator if they're mentally able to learn how
to use it.
They will keep the device for the next two or three months, in order to find out if
their ejection fraction is improving after the acute phase of myocardial
infarction. And if they are not improving, then it is time to consider the
implantable defibrillator. But during this interim time, we want to protect these
patients since they are sent home much earlier after revascularization than we
did in earlier years.
From the GISSI trial and others, we know there are patients who have
developed ventricular tachycardia, ventricular fibrillation or a long lasting nonsustained ventricular tachycardia in the first two days after myocardial
infarction. They have a higher risk of dying suddenly and these are also
patients that receive the wearable defibrillator. Plus patients that come to the
hospital in the very beginning in Killip class III or IV, which means they are in
severe heart failure in the acute phase of myocardial infarction.
Case Studies
Case Study 1
We will now discuss three cases, which really reflect the efficacy of the
wearable defibrillator in bridging the transitory risk. First is patient 1, a fifty-yearold female who presented in 2005 with an acute myocardial infarction, had a
new left bundle branch block, positive troponin, two times syncope. She was in
Killip class III and six hours after the beginning of chest pain, she came to the
hospital, got a stent in the LAD. It was single vessel disease. The echo showed
an ejection fraction of less than 25%.
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Figure 8: Case 1 Initial ECG
Figure 8 shows the electrocardiogram for case 1 and as you can clearly see,
there is a huge anterior myocardial infarction.
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Figure 9: Case 1 ECG after several days
Figure 9 shows her ECG a few days later, and you can still see the remainders.
There is scar tissue all over the anterior-inferior wall and this explains why this
patient will have, over the next months, a risk of dying suddenly that is higher
than the ones that we do revascularize but end up with a better ejection
fraction.
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Figure 10: Case 1 ECG after several days
Figure 10 shows the woman's ECG after three weeks. She was sleeping and in
the middle of the night, after these extrasystoles, the device triggered because
ventricular fibrillation occurred. After about 33 or 35 seconds, her husband lying
next to her noticed that she just kind of jumped up; the alarm of course went off
earlier. Without the device, she would have been found dead the next morning,
without her husband knowing that this had occurred. This is a typical example
of about 30 seconds and then the wearable defibrillator triggered and
resuscitated her, it prevented her from dying. Now she is doing fine after one
and a half years.
Case Study 2
The second case is a 68-year-old male, with inferior myocardial infarction. This
occurred 11 years ago. In the same year he had CABG bypass surgery and
was fine until August of this year. So, he lasted 11 years as New York class I,
no angina, and the ejection fraction is unknown. But in August this year he
showed up in the hospital with an acute anterior myocardial infarction and at
that time he was already in cardiogenic shock. The LAD was occluded,
physicians had to insert an intra-aortic balloon pump. The ejection fraction,
measured one day afterward, was about 20%. In the early phase, two stents
were implanted, in the LAD and since he has had bypass surgery--probably the
reason he went into cardiogenic shock after the graft to the right coronary artery
was occluded--another stent was put in the right coronary artery, the RCA graft.
The patient recovered from the cardiogenic shock. The wearable defibrillator
was given to him after the third day in the hospital. Two weeks later he was
discharged home.
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Figure 11: Case 2 ECG during MI
Figure 11 shows Case 2's electrocardiogram during the acute phase of
myocardial infarction. You can clearly see this is a large anterior myocardial
infarction. What made him go into cardiogenic shock isn't known. He kept the
wearable defibrillator, and after 2.5 months, again in the middle of the night, the
wearable defibrillator recorded the following, Figure 12.
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Figure 12: Case 2 ECG after 2.5 months
This ECG shows a sinus rhythm and then, all of a sudden, the onset of very
rapid ventricular tachycardia. This went on for about ten minutes.
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Figure 13: Case 2 ECG, after walking
Figure 13 shows the next ten minutes. As soon as the device detected the
arrhythmia he woke up from sleep and pushed the response buttons. The
device withheld the shock because he was conscious. We taught him not to
release the buttons as long as he was conscious. He just pushed the buttons
continuously for ten minutes while his wife called the EMT. When the EMT
came, he was still conscious.
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Figure 14: Case 2 ECG, after amiodarone
The EMTs gave him a shot of amiodarone, 150 mg, and then the arrhythmia
stopped, see Figure 14. It terminated spontaneously. So he had this arrhythmia
going on while being continuously conscious for about ten to fifteen minutes
until the emergency workers came. If he had fallen unconscious, the device
would have shocked him out of this arrhythmia. The device saved his life by
keeping him alive until the emergency crew showed up.
Case Study 3
The third case is a 77-year-old male who came into the hospital in October with
an acute myocardial infarction. He was already in New York class III. His
coronary angiography showed occluded LAD, the circumflex artery almost
occluded, and he had an ejection fraction of 15%. A stent was put into the LAD
and circumflex artery and he received the wearable defibrillator after the
second day in the hospital. Five days after the acute myocardial infarction, he
was put into a normal ward. Because of his age, he couldn't be sent home
immediately. Five days after the acute myocardial infarction, he received two
shocks from his wearable defibrillator. It shocked him out of ventricular
tachycardia but he ended up being in severe heart failure and died six days
later, six days after this VT event occurred.
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Figure 15: Case 3 ECG, on admission
Figure 15 shows case 3 in the acute phase of myocardial infarction: right
bundle branch block configuration with huge myocardial, anterior myocardial
infarction.
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Figure 16: Case 3 ECG, after five days
Figure 16 shows his ECG later. The ECG did not get the onset of the
arrhythmia, but, again, it was a very rapid ventricular tachycardia that was
hemodynamically ineffective that means he was very woozy and he became
unconscious.
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Figure 17: Case 3 ECG, during shock
Figure 17 shows that the device shocked him out of very rapid ventricular
tachycardia. Without the device, he would've been found dead in the ward by
the nurse during the night. But unfortunately he was so sick that he died later
due to heart failure.
Post-Op Patients
Patients early post-op have a higher risk of dying suddenly--specifically the
ones who have a bypass surgery, and show a low ejection fraction of 30% or
less. If ventricular function does not improve after bypass surgery or even valve
surgery, within the early phase, the first six days, our unit tends to give them
the wearable defibrillator.
Specifically, if they have non-sustained VT episodes in the intensive care unit it
is felt that that these patient need protection for the next one or two months in
order to become what could be called the MADIT II criteria patients. Even if
they have had revascularized ventricles they still are at high risk.
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Figure 18: Post-Op Patient
Figure 18 shows the ECG of a 56-year-old female and, again, the device is
able, until the patient becomes unconscious, to withhold the shock. You can
see here the onset of the arrhythmia. It goes on for a minute or two, and the
patient then presses the button and the device withholds the shock because
she was still conscious. Then the arrhythmia stopped spontaneously and the
patient did not receive a shock. So the possibility of withholding the shock with
this device seems to be very important.
The Magdeburg Experience With The
Wearable Defibrillator
At Magdeburg we have had considerable experience with the wearable
defibrillator. It has been used with 131 patients, 26 of them females. The mean
ejection fraction was 26%. The mean duration of use was 95 days. Some
patients had it only for a few days but these were not the ones post-myocardial
infarction. One patient still wears the defibrillator after more than three and a
half years. She's a circus artist with long QT syndrome and since she has type
III long QT syndrome, she completely refused an implant. Doing these tricks in
the circus on the trapeze she did not want to have the defibrillator implanted.
But when she is at home, at rest, or she's sleeping, she has a tremendous
number of VT, non-sustained torsades episodes. She loves the device and she
refuses to have an implantable device until she stops performing in the circus.
Leaving this one case aside, the maximum was 39 months: that was a patient
awaiting a heart transplant.
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Figure 19: Inclusion Criteria
Figure 19 shows the inclusion criteria at Magdeburg for a wearable defibrillator.
There were 72 patients with post-myocardial infarction, we have 26 patients
post-CABG, and we have 15 on the transplant waiting list. For other there are
various reasons, specifically, the risk identification in patients that have had
syncope. If they have a Brugada or long QT or other inherent arrhythmia risk,
we give them a wearable device, until we find out if the patients are safe or
need an implantable defibrillator. The majority are the ones that have had an
acute myocardial infarction with a low ejection fraction.
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Figure 20: Results
Results
Figure 20 summarizes our experience from these 131 patients: four patients
died, two of non-sudden cardiac deaths, two of sudden cardiac deaths without
the wearable defibrillator-- they either refused to use it or took it off. One took it
off because he wanted to take a shower but after the shower he thought he
didn't need the device anymore and after a few hours he died due to arrhythmic
causes. There are seven patients in the group that later on received heart
transplantation. The results of the Magdeburg experience: 11 appropriate
shocks in eight patients, three that clearly showed ventricular fibrillation and five
showed very rapid hemodynamically ineffective ventricular tachycardia. And
non-sustained VT in two-thirds of our patients detected by the Internet.
After three months, twenty-seven out of 98 patients received the ICD
implantation in the group of post-MI patients, the CABG patients. The risk
stratification of four out of 15 and the heart transplant 13 out of 15, then
received heart transplant.
Some False Alarms
Of course there were a few complications. There were false alarms due to
oversensing, though this is much better in the recent device than the earlier
devices. The electrodes are much better. There is less noise, which causes
fewer inappropriate alarms--- not shocks, only alarms. If the patient moves in
the back with these electrodes on you can have these false alarms, but there
was never a false shock except in one patient. That was a 75 year-old lady
walking on crutches after orthopedic surgery. When the alarms went off she
couldn't put aside the crutches and she got a shock. That's the only one that
got a shock, an inappropriate shock from noise due to electrode movement on
the skin. And we have had three other inappropriate shocks that were not due
to noise.
There was one episode of ventricular fibrillation that was correctly detected by
the device but, unfortunately, that was in a very early phase of the wearable
defibrillator and the patient had put the electrode patches on the wrong side so
it could not effectively defibrillate. This cannot happen anymore because of a
modification to the device.
Conclusion To Section 2
In conclusion, the wearable cardioverter defibrillator is an effective approach to
protect patients who have a transitory risk of dying suddenly until definitive risk
stratification has been performed, or the risk of ventricular tachycardia and
ventricular fibrillation occurrence has definitely decreased. The wearable
defibrillator is a safe and reliable tool to terminate ventricular tachycardia and
ventricular fibrillation, has a tolerably low complication rate, and may contribute
to reduced health care costs by preventing unnecessary ICD implants.
Section 3: Risk of Sudden Death In
Non-Ischemic Cardiomyopathy: A
Question Of Timing.
By: Leonard Ganz, MD,
Director of the Electrophysiology Service,
University of Pittsburgh,
Pittsburgh, Pennsylvania, USA
INTRODUCTION
Based on a detailed case presentation of a patient with non-ischemic
cardiomyopathy, this section discusses risk stratification for sudden death and
the role of the wearable defibrillator.
PURPOSE AND OVERALL GOAL
The purpose of this section is to present evidence that an external defibrillator
vest provides protection to patients during these waiting periods during which
ICD implantations are proscribed
OVERVIEW
This section provides a case study of a patient with non-ischemic
cardiomyopathy and discusses risk stratification for sudden death:




Introduction
Case Presentation
The Risk Of Sudden Cardiac Death In Non-Ischemic Cardiomyopathy
Conclusion
SECTION OBJECTIVES
After completing this section of the activity the learner should be able to:


Describe one case and follow up that shows the benefits of a wearable
defibrillator
Discuss issues of risk stratification in non-ischemic cardiomyopathy.
Introduction
We will begin with a detailed case presentation of a patient with non-ischemic
cardiomyopathy, and then discuss what we know about risk stratification for
sudden death in non-ischemic cardiomyopathy.
Case Presentation
Patient A is a 59 year-old man who was admitted to a community hospital with
a one-week history of progressive exertional dyspnea. He was very active; he
regularly went on walks and over a week or so he found that he was getting
increasingly breathless doing the same amount of activity that he usually did.
He denied having chest pains, palpitations, syncope or near-syncope.
Interestingly, he was told that he had a left bundle branch block about 30 years
prior, which would have made him about 29. These records we're not available.
He claims that he had a nuclear study at that time and it was normal. That
would have been very early in the era of nuclear cardiology.
The family history was non-contributory. He was taking no medications. He had
quit smoking years before and drank alcohol in modest amounts. He said that
he had had upper respiratory symptoms several weeks prior to his
presentation.
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Figure 1: ECG
Figure 1 shows Patient A's ECG. He did in fact have a very wide left bundle
branch block pattern, and there was a prior history of left bundle branch block.
He had an echocardiogram at the outside hospital, which showed a mildly
enlarged LV with severe global hypokinesis and an ejection fraction estimated
at 15 to 20%, a left ventricular end diastolic dimension of 6.7 cm, left atrial
enlargement, and mild pulmonary hypertension. He was transferred to a tertiary
care hospital where a coronary angiogram revealed normal coronary arteries.
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Figure 2: Left Ventriculogram
Figure 2 shows his left ventriculogram in the ROA view.
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Figure 3: Telemetry
And Figure 3 shows telemetry of his ECG. He had a lot of non-sustained VT on
telemetry and a close inspection shows PVCs as well.
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Figure 4: More Telemetry
But this patient had more than the usual share of monomorphic appearing VT,
see Figure 4. This concerned his physicians. He had no prior history of syncope
but the physicians were still concerned, due to the ambient ectopy. He had mild
heart failure when he came in and after two doses of lasix his heart failure was
almost resolved.
He was started on an ACE inhibitor, carvedilol, and digoxin. Because the
physicians were concerned, they elected to do a diagnostic electrophysiologic
study. In a patient with non-ischemic cardiomyopathy, a diagnostic EP study is
not always definitive. You will likely find either nothing or ventricular fibrillation.
The likelihood of inducing monomorphic VT in a patient with non-ischemic
cardiomyopathy is relatively low. He had a slightly prolonged H-P interval, a
very wide QRS complex, but despite an aggressive stimulation protocol, no
inducible VT or VF. Current guidelines preclude ICD implantation in a patient
like this because he had just been diagnosed with a non-ischemic
cardiomyopathy.
A LifeVest was recommended as a bridge to an ICD when he could fulfill the
implant criteria. It is not the hospital's standard practice to recommend
wearable defibrillator vests in all patients with non-ischemic cardiomyopathy. It
is a clinical judgment.
The suggestion was rejected by his insurance company with the explanation
that it was still only an investigational therapy. The hospital appealed twice and
the second appeal was finally successful, so ultimately he was discharged with
the wearable defibrillator vest five days later.
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Figure 5: Wearable Defibrillator Vest
Figure 5 shows the type of vest he was provided.
Follow up: Patient A
Two weeks after he was discharged from the hospital he had to go to the
emergency room. His wife was awakened by an audible signal from the
LifeVest that essentially said to call 911. He was unaware of any problem
although, on further questioning, said he was having an odd dream.
The ER did not have the Internet information transmission set up yet. But the
LifeVest was interrogated. These devices initially give you an audible signal-actually a vibration signal then an audible signal--so it takes longer for a
LifeVest to deliver therapy than an implantable defibrillator. Electrophysiologists
are accustomed to seeing patients in the office who have gotten a shock from
their defibrillator. In the early age of defibrillators, this was equated with a life
saved, but it is now known that many people get shocks from their defibrillators
for non-sustained VT which would have been hemodynamically tolerated, or
they get shocked from their defibrillator for a ventricular arrhythmia that
would've stopped on its own and wouldn't have been life threatening.
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Figure 6: Interrogation of Patient A's Vest
Information from the vest, Figure 6, is displayed in two channels. The top two
lines are the same thing happening simultaneously. It shows a sinus rhythm
with the patient's left bundle branch block. The patient develops a PVC and
then a rapid polymorphic VT or a VF. It starts at about 18 seconds. He and his
wife were in bed, and he didn't hear the audible signal to push the button.
Then the vest went through all of its different alerts and the shock was
delivered at about 58 seconds. We have a pretty good sense that this rhythm
doesn't often stop on its own after 40 seconds. So it's fairly clear that this was a
patient whose life was saved by the LifeVest.
ICD Implantation
Patient A had an ICD implanted the next day for secondary prevention. Now
that he's survived a cardiac arrest, it's covered by all insurance companies.
Two weeks after the implant the patient was able to host a high school
graduation party for his twin son and daughter.
At five-month follow-up, he'd had no ICD therapies. He's New York Heart
Association class II on an ARB, carvedilol, spironolactone and digoxin. Six
months after his initial presentation his ejection fraction has shown no
improvement despite this medical therapy and, if anything, his ventricle has
dilated further despite all of our best efforts. And he now has moderate mitral
regurgitation that he didn't have before.
The Risk Of Sudden Cardiac Death In
Non-Ischemic Cardiomyopathy
There are two clinical trials covering this. The DEFINITE and SCD-HeFT trials.
DEFINITE did not achieve statistical significance but was a relatively small trial.
SCD-HeFT did achieve statistical significance for the overall population but
when you break the data down to just the non-ischemics, it didn't quite reach
statistical significance.
Nevertheless, taking this data together, CMS issued a national coverage
decision, which initially allowed ICD implantation for patients with non-ischemic
cardiomyopathy and ejection fraction less than or equal to 35%, but nine
months after the initial presentation, three months if the patient was enrolled in
a registry.
Since all of our Medicare patients receiving prophylactic ICDs are enrolled in
the ICD registry, patients may be implanted three months after the diagnosis of
non-ischemic cardiomyopathy.
When we're looking at a patient with newly diagnosed non-ischemic
cardiomyopathy, that patient can fall into one of three categories.
1. Recent Onset
It may be that the cardiomyopathy is really of recent onset and potentially
reversible. And those conditions that might be reversible include myocarditis,
peripartum cardiomyopathy, and tachycardia-induced cardiomyopathy. And
these may all improve. There are really no data that suggest that if the LV
recovers, the risk of sudden death is eliminated. The concern is the transition
periods in which you have active remodeling, either for the better or for the
worse with stretch fibrosis, remodeling may be associated with a higher acute
risk.
2. Recent diagnosis
It may also just be a cardiomyopathy of recent diagnosis. Which would mean
that it has been in existence for a while but only recently discovered. Patient A,
for example, had a history of symptoms over the previous week, and viral
symptoms two weeks before. The fact that he had a chronic left bundle branch
block and the fact that he was already dilated suggests that this could have
been the acute recognition of a chronic problem.
There have been some studies that have looked at markers of chronicity; these
include a very poor ejection fraction, a dilated ventricle, RV dysfunction or an
increased spherical shape to the LV. If patients have a chronic cardiomyopathy
but are just recently diagnosed then they're at some baseline level of risk on
the day that you meet them. And it's not clear whether improvement of the left
ventricle ejection fraction with medical therapy necessarily mitigates or
eliminates this risk.
3. Chronic Condition
And the third possibility with a patient with cardiomyopathy, is that it is a truly
chronic condition. The patient has had it for a long time, and may have
documented poor ejection fraction for a long time, and those patients would be
at their baseline level of risk. It's also possible, if they've already survived ten
years, that they don't need a defibrillator, either internal or external. These
patients fulfill criteria for getting an ICD but if they had had one put in ten years
ago, or eight years ago, or five years ago, they could have done no better than
they did without the device.
New Data from the DEFINITE Trial
There's some very intriguing data that's been published relatively recently from
Alan Kadish and his colleagues of the DEFINITE study. Looking at timing, as it
relates to non-ischemic cardiomyopathy and the risk of sudden death. In the
DEFINITE trial there was no time prohibition for enrollment of patients in the
trial. They didn't have to have an established cardiomyopathy for a certain
period of time. But, the trial did ask investigators not to enroll patients with a
reversible cardiomyopathy. So, they looked at the patients in the DEFINITE trial
who were randomized to defibrillator or no defibrillator and then divided them by
the time of diagnosis of cardiomyopathy to the time of randomization. And since
the two cut points that CMS seemed to be interested in were three months and
nine months, they did the analyses both ways.
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Figure 7: Probability of Survival, 3 Months
Figure 7 shows these data looking at a diagnosis of non-ischemic
cardiomyopathy for three months or less, or more than three months. They are
Kaplan-Meir survival curves for the probability of survival, with the dark line for
those with an ICD, and the dotted line for standard therapy. What this data
shows is that the ICD seems to confer substantial survival benefit for the
patients whose non-ischemic cardiomyopathy had been diagnosed less than
three months prior to the time of randomization. But if they had been diagnosed
more than three months earlier, if they had been randomized more than three
months from the time of diagnosis, there wasn't much benefit.
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Figure 8: Probability of Survival, 9 Months
Figure 8 shows the data with the cut point at nine months.The trend is the
same. Those with an ICD show a strong trend towards an improved survival
when patients were randomized nine months or less from the time of diagnosis,
p value .058. Here again, if it's more than nine months, there doesn't seem to
be any benefit. This is intriguing data. We don't know when these patients
developed cardiomyopathy.
Highest Risk Early
This seems to suggest that the risk is highest early in these patients and the
current CMS prohibition of implanting ICDs may result in a lot of these patients
dying. This is the only trial data we have so far but the message is intriguing
and very concerning. Whether these patients have a chronic cardiomyopathy
and just recently came to attention because they developed heart failure or they
have a new onset cardiomyopathy, the highest risk in these patients seems to
be early.
It is difficult to differentiate an acute cardiomyopathy, and in particular who
might get better and who might not, or chronic cardiomyopathy. Regardless of
the type of cardiomyopathy, we really don't have any data that tell us whether,
when ventricular function gets better, the risk goes away, either in the long term
or in that transitional risk period. The DEFINITE data suggests that the early
period constitutes the most substantial risk for these patients.
Conclusion to Section 3
An external defibrillator vest provides protection to patients during these waiting
periods during which ICD implantations are proscribed. This is a great solution
for patients who are in these gap periods who might have a substantial risk of
sudden death.
Some Further Issues
What are the problems with the wearable defibrillator?
First of all, the patients have to be taught that they are at a higher risk of dying
suddenly. This is why we need protection for a short time. We have to tell the
patient the implantable ICD itself is not without risk. And there is the socialeconomical-financial issue.
The training and teaching period is extremely important. But with training, the
acceptance is extremely good. I think it's the teaching issue that we have
discovered in the last two or three years, that we have to do better. The bottom
line is that with appropriate patient education the device is very acceptable to
patients.
Does this focus only on PCI Patients?
It's just the acute PCI patient we've focused on here. These patients, they have
their PCI and after the PCI they immediately get the device. So, patients come
in with an acute myocardial infarction; they all get the acute PCI for acute
myocardial infarction. The next two days we keep them either in the chest pain
unit or in the normal ward and then we do the echo study and then we decide if
they have an ejection fraction of 30% or lower we start to teach them to use the
device and send them home with the device.
Unfortunately, we were hoping that opening the vessel in those patients that
come very early with a poor ejection fraction, that they would improve. But they
do not. So there are a few studies that are contradicting studies. If you
remember the Solomon study on the VALIANT trial that clearly showed that the
highest risk, about 2.5% sudden death, in the first six weeks after myocardial
infarction. There are other data. Then the curve goes very low and ends up
being 2% per year in the chronic phase.
On the other hand, data we coordinated for Finland showed completely the
opposite: that gradually the longer you live, the risk of dying suddenly gets
higher. So that is in favor of the implantable device. Then the other Solomon
data, that was the enalopril study, shows that about 36% recover in the first
ninety days after myocardial infarction. But there were also patients with
ejection fractions of 55, even normal ejection fractions -- but of the ones that
had ejection fractions below 55 %, only 36% recovered. There are 36% who
recover, who probably have a low risk of dying suddenly, but the remainder,
they still continue if we take ejection fraction as the most important risk factor.
So I think the incidence of recovery is still unknown and these, the studies that
exist, did not enroll patients with PCI treatment. The acute treatment of
revascularization for acute myocardial infarction is up to interpretation. We don't
know that. But I personally, I'm tremendously disappointed and would have had
- would have hoped - that these patients would have recovered in higher
percentages. Unfortunately, they do not do this.
Are there studies planned to evaluate where the wearable cardioverter
defibrillator can best be used?
Yes, there is at least one study in collaboration with ZOLL and Lifecor. And that
is looking at the early post-infarct period where we know that certain patients
are at high risk for at least a certain time until they became eligible for
implant. Or we have them in a stage where we have data that would suggest
that the implantable defibrillator can improve survival and there's this obvious
gap that for some people early post-infarct is a high risk period and we have no
therapy for them. So it's an obvious potential use of the wearable defibrillator.
Why do cardiac surgeons still insist on implanting ICDs in patients who
are waiting for heart transplant?
We know that the waiting period is quite long but I think even with six months
the device implanted for only six months, or even a year, is far too expensive
and also sometimes troublesome. You have the risk of infection. I think if the
patient data shows, the cardiac surgeons would take a little bit more time and
use their technicians to teach their patients on the waiting list to use the
wearable device. It would certainly lower the cost of heart transplants
significantly, specifically if the waiting time gets longer. The implantable ICD is
not a solution to bridge this risk of waiting for heart transplant. I don't
understand why they're not doing it.