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Acta Médica Costarricense
On-line version ISSN 0001-6002Print version ISSN 0001-6012
Acta méd. costarric vol.55 n.1 San José Jan./Mar. 2013
Original
Primary
and secondary prevention of sudden cardiac death in a hospital of the
social
security system in
Hugo Arguedas-Jiménez,1
Oswaldo Gutiérrez-Sotelo2
Cardiology Department, “Dr.
Rafael Ángel Calderón
Guardia” Hospital,
Abbreviatons:
ICD,Implantable
Abstract
Background:
Several studies have demonstrated
the efficacy of implantable cardioverter defibrillators
in the prevention of sudden cardiac death. The validation of this
evidence has
to be assessed through various registries. The objective of this study
was to
describe the main epidemiological and clinical characteristics of
patients who
were referred to a tertiary hospital in
Methods: A
retrospective observational cohort study, which included all patients
who were
treated with a cardioverter-defibrillator
implantable
in the “Dr. Rafael A. Calderón
Guardia” hospital between 2007 and 2011.
Results: Twenty
three patients were included. The mean age was 55 ± 18 years. Ischemic
heart disease was the most frequent etiology (10 patients). Twenty
patients had
functional class I or II and the mean ejection fraction was 0.38 ±
0.17.
In 18 patients, the cardioverter-defibrillator
was
implanted for secondary prevention. Five patients had an early
complication;
all of them had dual-chamber devices: 2 minor hematomas, 1 coronary
sinus
dissection, 1 right atrial lead
displacement, and 1
cardio embolic stroke. From a total of 101 therapies (in 8 patients),
94 were
appropriate (in 5 patients) and 7 were inappropriate (in 3 patients); 2
of the
latter 3 patients had a history of atrial
fibrillation episodes.
Conclusion:
This
registry shows that the majority of implantable cardioverter-defibrillators
implantations are performed as a secondary prevention, with a high rate
of
adequate therapies and a low rate of inadequate ones. The registry
allowed an
assessment of the indications and complications of this device therapy.
Key words:
Implantable
defibrillators, sudden death, arrhythmias.
Several
randomized controlled trials have demonstrated
the effectiveness of automatic implantable cardiac defibrillators (ICDs), reducing mortality for SCD in primary and
secondary
prevention for these patients,8-10
and
its superiority against drug treatment. Secondary prevention is defined
as
those measures applied after an episode of aborted SCD or an episode of
sustained ventricular tachycardia (VT), with or without hemodynamic
involvement. Primary prevention regards to those measures taken without
occurring any such events. International consensus management
guidelines have
been established 9 and consequently, there has been an
increase in
the overall number of implants, therefore the evidence applied to the
particular
situation in each population center must be evaluated. The only way to
achieve
this is by conducting surveys and records to compare results with other
centers
and meet the populations who receive ICD´s.
10-14
The aim of this study was to describe the main epidemiological
and
clinical characteristics at the time of implantation, as well as
knowing the
immediate and late complications of the population with an ICD, both
for
primary and secondary prevention, at a third level hospital in Costa
Rica.
Methods
An
observational, cohort, restrospective
study was made at the “Dr. Rafael Ángel Calderón Guardia” Hospital, in
Data
collection
The total
number of patients who received an ICD was
taken from the database of registered procedures in the hospital´s
Haemodynamics Laboratory, -established in
2002 -,
from the records of device providing companies and from clinical
records
requested to the Archive and Microfilm Service. Data was analyzed
regarding
demographic characteristics, cardiovascular history, history of supraventricular and ventricular arrhythmias,
implant
characteristics and programming devices, intraoperative
and long-term complications as well as the occurrence of events and
therapies
provided by the devices. Demographic data and dates of birth and death
were
corroborated with the Civil Registry of Costa Rica´s
database. Death records were last revised on January 6, 2012.
Information
regarding the events stored in the device´s
memory was based primarily on records made by the suppliers, which
includes a
monitoring report after each appointment.
ICD´s
provide three types of therapy: rapid pacemaker stimulation at a higher
frequency than VT, R wave-synchronized shock (cardioversion)
and unsynchronized shock (defibrillation) to reverse ventricular
fibrillation
(VF), Figure 1.
Therapy was considered appropriate when the device
detected
properly an episode of ventricular arrhythmia and administered one
programmed
therapy, while inappropriate therapy was that which made an inadequate
discrimination of an episode of supraventricular
arrhythmia, or over-sensing extracardiac
signals as myopotentials, or
electromagnetic interference.
“Electrical storm”, defined as the occurrence of three or more
episodes of sustained VT or VF, within a 24 hour period, each separated
from
the previous one, at least 5 minutes of ventricular arrhythmia-free
interval.
Early complication was defined as that which occurred in the first 30
days of
device implantation, and late complications were those which occurred
after
that period. A minor complication was that one which did not require a
new
intervention, hospitalization, or imply a risk to the patient’s life.
Information
was recorded on a data collection sheet
based on the formula used by the Implantable Cardio-Defibrillator
Registry of
the Spanish Cardiology Society (available at
http://www.secardiologia.es/images/stories/
file/arrhythmias/national-record-dai2010.pdf).
Studied
Patients
The study
included all patients who had an ICD were
registered in the database until 2011. Inclusion criteria were: age
over 18
years, without excluding gender, ethnicity, country of origin or
nationality,
and who had undergone implantation of an ICD for primary or secondary
prevention
of SCD. We excluded patients who haven´t
had at
least one follow-up appointment in the Cardiology Department.
Statistical
Analysis
Numerical
results were expressed as means and standard
deviations. Being a small population of patients, nonparametric
statistics were
used and expected event During the study
period, a
total of 25 devices were frequencies were compared using the chi-square
test. T
h e implanted. Information was available only for 23 patients. In
Kaplan-Meier
method, cumulative survival tables and the 2 cases, the clinical record
was
lost and there was noMantel-Cox test, were
used to
perform comparisons over possibility of tracking and knowing the
clinical
variables. time, until the occurrence of
events in the
groups of primary Between 2007 and 2009 only 5 devices were implanted,
or
secondary prevention. A value of P <0.05 was considered while
between 2010
and 2011, 18 (p <0.05 between both significant. Statistical analysis
was
performed with SPSS, periods). The mean age of the 23 patients was 55 ±
18 years. version 17.0.
Results
During the
study period, a total of 25 devices were
implanted. Information was available only for 23 patients. In 2 cases,
the
clinical record was lost and there was no possibility of tracking and
knowing
the clinical variables.
Between
2007 and 2009 only 5 devices were implanted,
while between 2010 and 2011, 18 (p <0.05 between both periods). The
mean age
of the 23 patients was 55 ± 18 years.
Although
implants were more frequent in male persons
(16 men), the difference was not significant (Table 1).
Underlying
cardiopathy, ejection fraction, functional
class and
basal rhythms.
Ischemic
heart disease was the most common etiology
(10 patients), followed by 8 patients with non-ischemic dilated cardiomyopathy (NIDCM), 2 with hypertrophic cardiomyopathy and 3 with channelopathies
(2 Brugada syndrome and 1 with long QT
syndrome,
Figure 2). Most
patients were in functional class I or II at the time
of
implantation (20 patients). Only 2 patients were in functional class
III and
one was in class IV. Most of the population had moderate or severe
impairment
of the FE, with a mean of 0.38 ± 0.17, and in about one third of the
population was <0.25. At the time of implantation, 17 patients were
in sinus
rhythm and five in atrial fibrillation
(AF). Nine
patients had a previous event of FA. Five patients had left bundle
branch block
bundle, 3 right bundle branch, 2 had a
first-degree atrioventricular block and 1
had Sick Sinus Node Syndrome.
Indications
and clinical arrhytmias
Out of 23
patients analyzed, 5 received an ICD for
primary prevention and 18 for secondary prevention. The criteria for
implantation in primary prevention were: severe ventricular dysfunction
in 4
patients with NIDCM (1 with acute low cardiac output) and one with
hypertrophic
cardiomyopathy, the latter two had nonsustained VT. The criteria for implantation
in secondary
prevention patients were: symptomatic VT or VF in 16 patients and
syncope or
symptoms of low cardiac output due to VT or VF induced during an
electrophysiology
study in 2 patients (Figure
2).
Concomitant
medication
According
to the type of population to whom the device
is implanted, most of them take beta blockers, aspirin, angiotensin
antagonists and statins (Table 1). Fifteen
secondary prevention
patients were medicated with amiodarone,
while only
one primary prevention patient used it.
First
implant and replacement
A total of
18 devices were first implants, while 5
were generator replacements. The cause for the replacement was the
depletion of
the battery in all cases. The average time until replacement was 5.83 ±
2.55 years, with a minimum of 342 days, in a patient with an accessory
pathway
and incessant ventricular tachyarrhythmiasm,
triggered by paroxysmal AF, and a maximum of 7.42 years (implanted in
2000), in
a patient with non-revascularizable
ischemic heart
disease and spontaneous sustained VT, which never repeated nor
registered other
events. One patient who previously underwent battery replacement, and
after
having checked that the electrode worked improperly, had a new
ventricular
electrode placed, and the dysfunctional ventricular electrode was left
in the
same position. In the other four cases, the previous electrodes were
used,
after checking they were in good condition.
Threshold
tests, device type and initial programming
Defibrillation
threshold test was performed in 15
patients. The main reason why it was not performed was the lack of an
available
anesthesiologist. The effective mean threshold was 24.2 ± 5.7 Joules
and
an average of 1.5 ± 0.5 shocks per patient was applied. All devices
were
implanted in the haemodynamics laboratory
by an electrophysiologist cardiologist,
and placed in position by
subcutaneous subclavian venipuncture.
Unicameral devices were used in 2 patients, dual-chamber devices in 19
patients
and cardiac resynchronization devices in 2 patients. The anti-bradycardia pacing mode in 15 patients was DDD,
DDDR in 2, VVIR in 5 and VVI in one
patient. Prevention algorithms
right ventricular stimulation burned in 7 patients. Antitachycardia
pacing therapy is scheduled in at least one area of stimulation, in 16
patients.
Primary or
secondary prevention
When
comparing the demographic and clinical data of patients
who received an ICD for primary versus secondary prevention, no
significant
differences were found regarding age, gender prevalence, EF, functional
class,
medical history or medication use. The only significant differences
between
groups were greater use of amiodarone in
patients in
secondary prevention (already mentioned), and QRS interval duration in
the
secondary prevention group (p <0.05, Table 2).
Early
complications
Out of the
23 patients who received an ICD, 5 had
early complications, 3 of which were minor. Everyone had dual-chamber
devices,
a patient with NIDCM for primary prevention presented coronary sinus
dissection
and mild pericardial effusion, why not implanted coronary sinus
electrode. Two
patients developed a hematoma at the site of implantation of the
device, both
were managed conservatively. One of them took aspirin and clopidogrel
in the days prior to the implant, the other one was anticoagulated
with warfarin, had an International Normaized Ratio of 1 at the time of
implantation, and
resumed warfarin 48 hours later, but
developed a
hematoma 5 days after. It was solved with temporary discontinuation of
anticoagulant drugs and local compression. One patient suffered a right
atrial electrode displacement, with phrenic
stimulation 19 days after implantation. The electrode was repositioned
in the
right atrium appendage. The most serious complication occurred in a
functional
class III NIDCM patient, with EF = 0.35, chronic AF and non-sustained
VT, to
whom an ICD was implanted for primary prevention. “After the
defibrillation threshold test, sinus rhythm was recovered.” Despite
being
optimal anticoagulation before and during implantation, the patient
suffered a cardioembolic stroke two days
later, compromising the
territory of the left middle cerebral artery, and causing motor and
language sequelae (Table 3).
Follow up
and event description
The mean
follow-up of enrolled patients was 367
± 359 days. Of all primary prevention patients, only 1 had an
arrhythmic
event and therapy provided by the device was appropriate. In the
secondary
prevention group, 8 patients had events, 5 received appropriate
therapies and 3
received an inappropriate therapy. There were no significant
differences
between groups. The mean time until the first event in the primary
prevention
group was 774 ± 222 days, while in the secondary prevention group it
was
684 ± 148 days. There were no statistically significant differences
between groups (Figure
3).
In total,
101 therapies were administered, 49 of them
were appropriate antitachycardia pacing
therapies, 45
were appropriate shocks and 7 were inappropriate shocks. The patient
who
received more therapies had a total of 25, while two patients had 2
therapies
and 15 patients didn´t receive any.
Appropriate
therapies were applied for 32 episodes of VF and 62 VT episodes. The 7
inappropriate therapies occurred because of 5 episodes of AF and 2
other supraventricular tachycardias.
These occurred in 3 patients, 2 of whom had previous episodes of AF
before
device implantation and were in the secondary prevention group (Figure
4). Five
patients had an “electrical storm”; they were four secondary
prevention patients: 3 with ischemic heart disease and 1 with NIDCM.
These 4
patients haven´t recurred, after receiving
adjustment of antiarrhythmic medication
and
reprogramming therapy zones with an antitachycardia
pacemaker. The last storm case was a man with NIDCM, functional class
IV and FE
= 0.15, to whom an ICD with resynchronization therapy was implanted, as
a
rescue option for his advanced disease. He developed recurrent VT and
VF, and
received appropriate ICD therapies; however, he died three days later
because
of terminal heart failure and electromechanical dissociation.
Discussion
There was a low number of
annual implants in this center; however, there has been a significant
increase
in the last two years, similar to the global trend towards a linear
increase in
the number of implanted devices. Given its high costs,it must be considered that the number of ICDs implanted in each country depends on GDP
and health
expenditure, as well as the number of medical facilities that implant
the
devices. Therefore, inadequate budgets and the ability to provide
health
services in Costa Rica, could directly affect the availability and
implantation
of new devices, such as has occurred in other countries.11 Although
the average age appears to be lower in this study compared to other
reports,
its variation was in the previously reported ranges.12, 13 Underlying
heart disease was also distributed similarly, and ischemic heart
disease was
the most common, followed by NIDCM. 14 Despite the high
frequency of
chagasic myocarditis
in
Since in
this center implantation of an ICD is
considered after patients have optimal medical therapy, a high
proportion of
patients took all necessary medicines to control their heart failure
and low
EF. Also, all patients met any class I or II-A recommendations from
international guidelines for ICD implantation in primary prevention or
secondary prevention.16 Only two
patients
underwent electrophysiological studies for induction of ventricular
arrhythmias; this allows upgrading to class I recommendation in
selected
patients. The average EF in this study is similar to that published in
secondary prevention studies, there was a lower EF in the primary
prevention
group, as expected, due to the different indications for implantation,
although
this wasn´t a significant difference
compared
to the secondary prevention group.17 Usefulness of amiodarone in secondary prevention patients has
been
described, as a measure to prevent and reduce the number of therapies
provided
by the device, or to make them more tolerable by decreasing VT
frequency and
allowing the antitachycardia algorithms to
function.
In this series, this drug was also more frequently used in this
subgroup; a
primary prevention patient taking the drug, even when it has been shown
that it
doesn´t provide greater benefit in this
group,
compared with the ICD.18
The high
prevalence of AF found in the group is
consistent with other reports, in which it is associated with aging and
diseased populations, with low EF and heart failure symptoms. Permanent
AF
increases the risk of a ventricular arrhythmia and receiving
appropriate
therapy, whereas paroxysmal and persistent forms increase the risk of
receiving
inappropriate therapies, compared with the group without AF.
Being a
small study group, the series has an expected
number of complications. 20 They all occurred in patients
with
dual-chamber devices. Only one patient had a clear indication for an
anti-bradycardia pacemaker because of Sick
Sinus Syndrome.
Another 5 patients with left bundle branch block would have been
candidates for
tricameral device implantation. The
majority of
patients included in the ICD efficacy studies received an unicameral
device,
subsequent reports have shown a trend towards the introduction of
dual-chamber
devices, but the theoretical advantage of such models hasn´t
shown a clear superiority over unicameral models; 21 besides,
the
placement of an additional number of electrodes significantly increases
the
complication rate.22 It should be noted that the group of
patients
receiving a dual chamber ICD had a higher proportion of morbidities and
may
include some patients that had unsuccessful attempts to put a left
ventricular
lead. Tricameral ICD implantation
increases the risk
of complications such as hematomas, electrode displacement, coronary
sinus
dissection and cardiovascular death, 23 especially if they
are
taking anticoagulants or antiplatelet
therapy
concomitantly. Of course, any complication increases stay and hence
hospitalization costs.24
Between 15
and 31% of all shocks were inappropriate 25-27
and affect up to 15% of patients who received an ICD, 26-27
which
coincides with the number of inapproppriate
events in
this study. Most had previous episodes of AF and the shock was
triggered by a
misdiagnosed supra-ventricular tachycardia. Receiving inappropriate
shocks lead
to higher recurrence and mortality rates, so the use of more advanced
algorithms and improved programming should reduce them, 25 multicenter
randomizedstudiesarebeingmadeforthatpurpose.“Electrical
storm” has an incidence between 7, 10 and up to 25% per year, 26 as
applicable to populations with tri, uni-or
bicameral,
devices respectively, but also influenced by the different populations
that
receive uni or bicameral ICD´s.
These are mainly in patients with sustained ventricular arrhythmias or
high
risk of SCD, compared to those in which a cardiac resynchronization
capable ICD
is implanted, in which heart failure prevails. The series showed,
agreeing with
previous studies, increased risk of electrical storm in secondary
prevention
patients; however, most of these patients had an ischemic background,
in
contrast with the fact that NIDCM patients have a greater risk
according to
other reports.27 Most of these patients were managed
optimizing
medical treatment and reprogramming therapy modalities; the combined
use of
beta-blockers and amiodarone has shown to
significantly reduce the risk of shocks.28
The main
limitation of this study was the small
population size from a single center, which does not represent the
reality of
the rest of
This is
the first study to show the clinical
characteristics and criteria under which the devices have been
implanted in a
tertiary care center in
Conflict
of interest: The
authors have received financial and logistical support of the brand
representatives Saint Jude Medical and Medtronic, for academic
activities
organized by independent institutions.
Acknowledgment:
The
authors thank engineer Grace Vargas, product specialist of SUMEDICAL
Costa
Rica, for her help in finding and organizing track records of their
patients.
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