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Population-Based Analysis of Sudden Cardiac Death With and Without Left Ventricular Systolic Dysfunction

Heart Rhythm Research Laboratory, Division of Cardiology, Oregon Health and Science University, Portland, Oregon.
Journal of the American College of Cardiology (Impact Factor: 16.5). 03/2006; 47(6):1161-6. DOI: 10.1016/j.jacc.2005.11.045
Source: PubMed

ABSTRACT

We sought to evaluate the contribution of left ventricular (LV) dysfunction toward occurrence of sudden cardiac death (SCD) in the general population, and to identify distinguishing characteristics of SCD in the absence of LV dysfunction.
Patients who manifest warning symptoms and signs are more likely to undergo evaluation before SCD. Although prevalence of LV dysfunction in this subgroup may overestimate the prevalence in overall SCD, this is the only means of assessment in the general population.
All cases of SCD in Multnomah County, Oregon (population 660,486; 2002 to 2004) were prospectively ascertained in the ongoing Oregon Sudden Unexpected Death Study. We retrospectively assessed LV ejection fraction (LVEF) among subjects who underwent evaluation of LV function before SCD (normal: > or =55%; mildly to moderately reduced: 36% to 54%; and severely reduced: < or =35%). Of a total of 714 SCD cases (annual incidence 54 per 100,000), LV function was assessed in 121 (17%).
The LVEF was severely reduced in 36 patients (30%), mildly to moderately reduced in 27 (22%), and normal in 58 (48%). Patients with normal LVEF were distinguishable by younger age (66 +/- 15 years vs. 74 +/- 10 years; p = 0.001), higher proportion of females (47% vs. 27%; p = 0.025), higher prevalence of seizure disorder (14% vs. 0%; p = 0.002), and lower prevalence of established coronary artery disease (50% vs. 81%; p < 0.001).
In this community-wide study, only one-third of the evaluated SCD cases had severe LV dysfunction meeting current criteria for prophylactic cardioverter-defibrillator implantation. The SCD cases with normal LV function had several distinguishing clinical characteristics. These findings support the aggressive development of alternative screening methods to enhance identification of patients at risk.

Full-text (PDF)

Available from: Sumeet S Chugh, Jul 27, 2015
Population-Based Analysis of
Sudden Cardiac Death With and
Without Left Ventricular Systolic Dysfunction
Two-Year Findings from the Oregon Sudden Unexpected Death Study
Eric C. Stecker, MD, Catherine Vickers, RN, Justin Waltz, MPH, Carmen Socoteanu, MD,
Benjamin T. John, MD, Ronald Mariani, EMT-P, John H. McAnulty, MD, FACC, Karen Gunson, MD,
Jonathan Jui, MD, MPH, Sumeet S. Chugh, MD, FACC
Portland, Oregon
OBJECTIVES We sought to evaluate the contribution of left ventricular (LV) dysfunction toward occurrence
of sudden cardiac death (SCD) in the general population, and to identify distinguishing
characteristics of SCD in the absence of LV dysfunction.
BACKGROUND Patients who manifest warning symptoms and signs are more likely to undergo evaluation
before SCD. Although prevalence of LV dysfunction in this subgroup may overestimate
the prevalence in overall SCD, this is the only means of assessment in the general
population.
METHODS All cases of SCD in Multnomah County, Oregon (population 660,486; 2002 to 2004) were
prospectively ascertained in the ongoing Oregon Sudden Unexpected Death Study. We
retrospectively assessed LV ejection fraction (LVEF) among subjects who underwent
evaluation of LV function before SCD (normal: 55%; mildly to moderately reduced: 36%
to 54%; and severely reduced: 35%). Of a total of 714 SCD cases (annual incidence 54 per
100,000), LV function was assessed in 121 (17%).
RESULTS The LVEF was severely reduced in 36 patients (30%), mildly to moderately reduced in 27
(22%), and normal in 58 (48%). Patients with normal LVEF were distinguishable by younger
age (66 15 years vs. 74 10 years; p 0.001), higher proportion of females (47% vs. 27%;
p 0.025), higher prevalence of seizure disorder (14% vs. 0%; p 0.002), and lower
prevalence of established coronary artery disease (50% vs. 81%; p 0.001).
CONCLUSIONS In this community-wide study, only one-third of the evaluated SCD cases had severe LV
dysfunction meeting current criteria for prophylactic cardioverter-defibrillator implantation.
The SCD cases with normal LV function had several distinguishing clinical characteristics.
These findings support the aggressive development of alternative screening methods to
enhance identification of patients at risk. (J Am Coll Cardiol 2006;47:1161–6) © 2006 by
the American College of Cardiology Foundation
Severe left ventricular (LV) dysfunction confers significantly
increased risk of sudden cardiac death (SCD) and is
currently the major indication for primary prevention with
the implantable cardioverter-defibrillator (ICD) (1– 4). In
See page 1167
the absence of severe LV dysfunction, ICD implantation for
increased risk of SCD is limited to a small subset of
conditions, such as hypertrophic obstructive cardiomyopa-
thy, the long QT and Brugada syndromes, and idiopathic
ventricular fibrillation (5). Large cohort studies have iden-
tified several other risk predictors, such as family history,
diabetes mellitus, obesity, and heart rate profile during
exercise (6 –10), indicating that determinants of SCD are
likely to be diverse as well as multifactorial.
In fact it has been postulated that patients with severe LV
dysfunction, such as those studied in the prospective pro-
phylactic ICD trials, may represent a minority of the sudden
death population at risk (11–14). However, the distribution
of LV function among cases of SCD has not been evaluated
in a U.S. subpopulation. A suitable approach would be
prospective and population based, with SCD cases being
ascertained from multiple sources such as first responders
and medical examiners as well as area hospitals (13,15).
Determination of the extent and distribution of LV
dysfunction among SCD cases in the general population
is also a logical first step in the identification of novel
predictors of SCD risk among subjects who do not have
LV dysfunction.
The Oregon Sudden Unexpected Death Study is an
ongoing investigation of SCD among all residents of a large
U.S. community (15). To evaluate the prevalence of LV
dysfunction among SCD cases in the general population, we
From the Heart Rhythm Research Laboratory, Division of Cardiology, Oregon
Health and Science University, Portland, Oregon. Dr. Chugh is supported by the
United States Centers for Disease Control and Prevention/ATPM TS-0660, the
Donald W. Reynolds Clinical Cardiovascular Research Center Grant to Johns
Hopkins University, NHLBI HL-04-001, and PHS Grant 5 M01 RR000334. Drs.
Stecker and John are recipients of postdoctoral fellowship awards from the American
Heart Association. Presented in part at the American College of Cardiology 2005
Annual Scientific Sessions (2005 Young Investigator Award to ECS for this
manuscript).
Manuscript received September 4, 2005; revised manuscript received October 17,
2005, accepted November 20, 2005.
Journal of the American College of Cardiology Vol. 47, No. 6, 2006
© 2006 by the American College of Cardiology Foundation ISSN 0735-1097/06/$32.00
Published by Elsevier Inc. doi:10.1016/j.jacc.2005.11.045
Page 1
performed a retrospective analysis of left ventricular ejection
fraction (LVEF) among patients who underwent LV func-
tion evaluation before SCD. To identify distinguishing
characteristics of SCD in the absence of LV dysfunction, we
performed clinical comparisons between SCD cases with
evidence of LV dysfunction and those with normal LV
function.
METHODS
Study population. All residents of Multnomah County,
Oregon (population 660,486), who experienced sudden
cardiac death between February 1, 2002, and January 31,
2004, were evaluated. Cases were identified from multiple
sources: the county emergency medical response system, the
medical examiner, and area hospitals. Detailed methods
have been published earlier (15). In order to be included in
this analysis, medical records were required with sufficient
detail such that LV function before SCD could be
established.
Case ascertainment. The county emergency medical ser-
vice, the medical examiner, and all public and private
hospitals participated in the study. Cases were identified by
emergency medical technicians, the office of the medical
examiner, and emergency department physicians, and phy-
sicians of record referred these cases to investigators for
screening. Missed cases were captured during weekly audits
of the ambulance run-sheets and medical examiner death
reports. Medical records were obtained from one or more of
the following sources: 1) emergency medical responders;
2) medical examiner; 3) hospital of record; 4) primary care
physician. After all available medical records were accessed,
investigators performed a detailed evaluation of each case,
which included analysis of the circumstances of death,
known medical history and any information from the index
hospitalization or autopsy. Cases were categorized as SCD
by a majority consensus of three cardiologists. Deaths were
categorized as sudden if they met the World Health
Organization criteria (16). Witnessed SCDs were those in
which cardiac arrests happened within1hofsymptom
onset. Unwitnessed SCDs were those in which patients
were found dead within 24 h of having last been seen alive
and in a normal state of health. All patients were included,
regardless of whether they underwent resuscitation. Patients
were excluded if death was not unexpected (e.g., terminal
cancer) or if non-cardiac etiologies of sudden death were
identified (e.g., trauma, drug overdose, or pulmonary
embolism).
Definitions. Left ventricular function was categorized by
the quantitative assessment of LVEF or qualitatively
reported LVEF as follows: normal: 55%; mildly or
moderately reduced: 36% to 54%; and severely reduced:
35%. Direct quantitative measurements of EF were
used only if confirmed as accurate in the echocardiog-
rapher’s assessment.
Patients were categorized as having hypertension, previ-
ous cerebrovascular accident, sleep apnea, or seizure disorder
if indicated in the medical record. Patients were categorized
as having diabetes or hyperlipidemia if directly indicated in
the medical record or if diabetes or cholesterol medications
were noted. Coronary artery disease (CAD) was defined as
coronary artery stenosis of 50% or documentation of
previous myocardial infarction (MI), coronary artery bypass
grafting, or percutaneous coronary intervention. Acute MI
at the time of arrest referred to: 1) documented acute MI in
the medical record; 2) fresh infarction or clot identified on
autopsy; 3) typical acute injury or infarct pattern on elec-
trocardiogram (ECG); or 4) a combination of elevated
troponin/serum creatine kinase-MB fraction (CK-MB) and
either ECG or clinical evidence for infarction. Ischemic
symptoms were defined as pain in the chest, shoulder, arm,
epigastrum, neck, or jaw or abrupt onset of dyspnea.
Assessment for potential bias. Comparisons of age, gen-
der, socioeconomic profile, and characteristics of cardiac
arrest were performed between patients with and without
assessments of LV function in order to assess for potential
selection bias. Geographic-based socioeconomic indicators
were determined by identifying the 2000 Census Bureau
Census Tract for each subject based on home address. For
the purpose of comparisons, the values of several preselected
parameters (17) associated with each tract were assigned to
all subjects residing in the tract, and mean values were
obtained.
Statistical analysis. All statistical analyses were performed
using SPSS 13.0 for Windows (SPSS Inc., Chicago, Illinois).
Continuous variables were expressed as mean values
standard deviation. Significance between groups was deter-
mined using two-sided independent-sample Student
t tests for continuous variables and Pearson chi-square test
(or Fisher exact test if expected cell count is 5) for discrete
variables.
RESULTS
Distribution of LV function among SCD cases evaluated
before cardiac arrest. During the two-year period, 714
residents of Multnomah County experienced SCD (annual
incidence 54 cases per 100,000 residents). The mean age
was 66 19 years, and 40% were female. Overall, 48% of
SCD cases were witnessed and 63% underwent attempted
resuscitation. Medical records from emergency medical
responders or the medical examiner were available in 704
Abbreviations and Acronyms
ARVD arrhythmogenic right ventricular dysplasia
CAD coronary artery disease
ICD implantable cardioverter-defibrillator
LV left ventricular
LVEF left ventricular ejection fraction
MI myocardial infarction
SCD sudden cardiac death
1162 Stecker
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LV Dysfunction and Sudden Cardiac Death
March 21, 2006:1161– 6
Page 2
cases (98%). A total of 121 cases (17%) underwent an
assessment of LV systolic function before SCD. There were
no significant demographic differences between those with
an assessment of LVEF and those without, aside from a
small difference in age (Table 1). Mean age of patients with
an LVEF assessment was 70 13 years, 44 (36%) were
female, and 80 (66%) underwent attempted resuscitation.
The LVEF was assessed by echocardiogram in 107 (88%),
by contrast left ventriculography in 13 (11%), and by
radionuclide ventriculography in 1 (1%). The exact date of
LV function assessment was known in 117 cases, and the
majority of evaluations were conducted within two years of
SCD (n 74; 63%). Of the 121 cases that underwent
assessment of LV function, 58 patients (48%) had normal
LVEF, 27 (22%) had mild to moderately reduced LVEF,
and 36 (30%) had severely reduced LVEF.
Indications for ICD implantation based on current cri-
teria. None of the 714 SCD cases underwent ICD implan-
tation before cardiac arrest. Among the subgroup that had
evaluation of LV function, severely reduced LVEF was
observed in 36 patients (30%) and would have been the most
common indication for prevention of SCD with a prophy-
lactic ICD. Other indications included previous cardiac
arrest without severely reduced LVEF (n 4) and high-risk
genetic conditions (n 2). Had all information been
available for all individuals before SCD, the majority of
cases (n 79; 65%) would not have qualified for ICD
implantation for prevention of SCD based on current
guidelines.
Distinguishing characteristics of patients with normal
LV function. As shown in Table 2, patients in the normal
LV systolic function subgroup were significantly less likely
to have documented CAD. Patients with normal LV
function also had a significantly younger mean age, higher
proportion of women, and higher proportion of seizure
disorder. All eight patients with a history of seizure disorder
had normal LV function. Average age was 60 12 years,
and five of these patients were female. One of these patients
also had a diagnosis of arrhythmogenic right ventricular
dysplasia (ARVD). This patient’s seizure disorder was
attributed to an intracranial arteriovenous malformation for
which surgical resection was performed. For the overall
subgroup of patients with seizure disorder, the most recently
used antiepileptic medications were phenytoin (n 2),
Table 1. Comparisons Between SCD Cases That Underwent Evaluation of LV Function
and All Remaining Cases of SCD
LVEF Known
(n 121)
LVEF Unknown
(n 593) p Value
Age (yrs) 70 13 66 19 0.02
Female 44 (36%) 238 (40%) 0.44
Witnessed 61 (50%) 279 (47%) 0.50
Resuscitation attempted 80 (66%) 370 (62%) 0.44
SES characteristics*
Median income $41,500 12,800 $42,200 12,800 0.59
Poverty (all ages) 13 5.5% 13 7.7% 0.53
Poverty (elderly) 10 6.2% 10 7.7% 0.97
Median home value $158,600 39,600 $164,800 62,200 0.38
High education (Bachelor’s degree) 25 15% 27 16% 0.42
*SES variables are based on Census Tract data. Analysis omits seven patients owing to incomplete information regarding
residence.
LVEF left ventricular ejection fraction; SCD sudden cardiac death; SES socioeconomic; VT ventricular
tachycardia.
Table 2. Clinical Characteristics of SCD Cases That Underwent Evaluation of LV Function
Reduced EF
Normal EF
(n 58) p Value*
Severe
(n 36)
Mild/Moderate
(n 27)
Age (yrs) 74 11 73 9.1 66 15 0.01
Female 9 (25%) 8 (30%) 27 (47%) 0.03
Attempted resuscitation 23 (64%) 19 (70%) 38 (66%) 1
CAD 27 (75%) 24 (89%) 29 (50%) 0.01
Prior SCD 2 (6%) 1 (4%) 3 (5%) 1
DM 11 (31%) 9 (33%) 19 (33%) 1
Hypertension 25 (69%) 19 (70%) 35 (60%) 0.27
Hyperlipidemia 21 (58%) 15 (56%) 23 (40%) 0.06
Seizure disorder 0 0 8 (14%) 0.01
Prior CVA 4 (11%) 5 (19%) 9 (16%) 0.85
Sleep apnea 4 (11%) 3 (11%) 6 (10%) 0.89
*p value for difference between any reduction in EF and normal EF.
CAD obstructive coronary artery disease; CVA cerebrovascular accident; DM diabetes mellitus; EF ejection
fraction; LV left ventricular; SCD sudden cardiac death.
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March 21, 2006:1161– 6
LV Dysfunction and Sudden Cardiac Death
Page 3
carbamazepine (n 3), phenobarbital (n 1), gabapentin
(n 1), and unknown (n 1). Two patients had electro-
encephalograms documented and both were abnormal, but
neither had epileptiform discharges present. Each of the
four witnessed cases in our analysis had a sudden cardiac
arrest with no seizure-like activity observed either preceding
or during the event.
On comparing the medication lists of patients with
reduced LV function with those of the normal LV function
group, no significant differences were identified for antiar-
rhythmic, antipsychotic, and antidepressant medications.
However, a significantly greater proportion of the normal
LV function group had an antiepileptic medication pre-
scribed (19% vs. 3%; p 0.01). The indication for prescrib-
ing antiepileptics for the two patients in the reduced EF
group was neuropathic pain, not seizure disorder.
Detailed clinical characteristics of subsets. There were 51
patients (42%) older than 75 years. Left ventricular dysfunc-
tion was significantly more prevalent among patients older
than 75 years (severely reduced LVEF: 41% of older group
vs. 21% of younger group; p 0.019). Among the 80
patients (66%) who had resuscitation attempted, 7 (9%) had
occurrence of recognized acute MI and 13 (16%) had either
acute MI or ischemic symptoms before the arrest. The rates
of MI and ischemic symptoms did not vary based on LV
function (Table 3). Of the seven patients with recognized
acute MI, death occurred within1hoftheonset of symptoms
in five.
A total of 112 patients (93%) had an echocardiogram
performed, of which 41 were inpatient and 71 outpatient
echocardiograms. The most common reasons for hospital-
ization among patients with inpatient echocardiograms
were chest pain or acute MI (n 10), congestive heart
failure (n 7), and chronic obstructive pulmonary disease
(n 3). For all echocardiograms, one or more indications
were available in 80 patients. Common reasons listed
included evaluation of LV function (n 28), dyspnea or
congestive heart failure (n 18), and murmur and valvular
disease (n 11). Predisposing conditions for SCD were
present in a minority of these patients, with severe aortic
stenosis in five patients and likely hypertrophic cardiomy-
opathy in one patient (septal wall thickness 19 mm). The
remainder of the patients with normal LV function (includ-
ing the one with ARVD diagnosed by other means) did not
have indicators of SCD risk on the echocardiogram.
DISCUSSION
Earlier cohort studies as well as the primary and secondary
prevention trials for SCD have established severe LV
dysfunction as the best available risk predictor for SCD
(1–4,18,19), but U.S. population-based evaluations have
not been conducted. The present community-based study
demonstrated that of the patients who had LV function
assessed before cardiac arrest, 52% had some decrease in LV
systolic function and 30% had severely decreased LV systolic
function. Therefore, based on current LVEF guidelines for
SCD prevention, only 30% would have qualified as candi-
dates for a prophylactic ICD. Overall, considering LV
dysfunction as well as other high-risk conditions, 65% of
these patients would not have met the criteria for ICD
implantation. Patients with SCD and normal LVEF were
younger, more often female, more likely to have a seizure
disorder, more likely to be taking antiepileptic medications,
and less likely to have an established diagnosis of CAD
compared with those with an abnormal LVEF.
The frequency of LV dysfunction in SCD from a
community-based study in Maastricht, the Netherlands, has
been reported (20,21). Among 200 cases of SCD with an
assessment of LV function available, 101 (51%) had normal
LVEF, defined as 0.50, and 38 (19%) had severely
reduced LVEF, defined as 0.30. If the LVEF criteria
from this study were applied to the present study, 53% of
our cases would have had normal LVEF and 26% would
have had severely reduced LVEF. Therefore, our results in
a U.S. population show similar trends for distribution of
severe LV dysfunction. In addition to the geographic
location, there are several important differences in how the
two studies were conducted. The Netherlands study was
limited to cases 20 to 75 years old, whereas our study
included all ages. Because the frequency of SCD increases
with age, older patients can account for a significant
proportion of cases. Indeed, in our study, patients over
75 years of age constituted 38% of the total SCD cohort
during this two-year period. In addition, the present study
collected and analyzed detailed information on comorbidi-
ties, permitting evaluation of potential alternative clinical
risk predictors of SCD. Finally, we were able to evaluate for
potential bias between the subgroups with and without
evaluation of LV function.
The findings from the present study confirm the need to
identify SCD risk predictors other than severe LV dysfunc-
tion in the general population. Severe LV dysfunction, the
current major risk predictor of SCD, was identified in only
30% of SCD cases. Even if all of the other risk predictors,
such as history of resuscitated cardiac arrest, the long QT or
Brugada syndromes, hypertrophic cardiomyopathy, and
ARVD, were taken into account, only 35% of SCD cases
Table 3. Diagnosis of Myocardial Infarction or Ischemic
Symptoms Among SCD Cases That Underwent
Attempted Resuscitation
Reduced EF
(n 42)
Normal EF
(n 38) p Value
STEMI 0 2 (5%) 0.22
Non–STEMI 1 (2%) 4 (11%) 0.19
Ischemic symptoms 3 (7%) 3 (8%) 1
Any of above 4 (10%) 7 (18%) 0.25
Only subjects in whom resuscitation was attempted were analyzed.
EF ejection fraction; SCD sudden cardiac death; STEMI ST-segment
elevation myocardial infarction.
1164 Stecker
et al.
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LV Dysfunction and Sudden Cardiac Death
March 21, 2006:1161– 6
Page 4
would have been identified as being at high risk for SCD.
Therefore, in a hypothetical ideal situation in which all of
these cases were to be evaluated before cardiac arrest, the
majority (65%), based on prevailing knowledge, would not
have met criteria for SCD prevention with the ICD
(1,22,23).
However, our findings identify other potential predictors
that may enhance risk stratification for SCD in the general
population. The logical first step in the search for alternative
risk predictors is a clinical comparison with SCD cases that
had normal LV systolic function (48% of evaluated cases in
the present study). This comparison showed a lower rate of
previously diagnosed coronary artery disease in the normal
LV function group. In general, there is a strong association
between SCD and significant CAD, and prevailing knowl-
edge would suggest that acute myocardial ischemia is likely
to be the overall dominant contributor to SCD (12,15,
24,25). In an earlier autopsy evaluation during the first year
of this community-based study, 75% of overall adult SCD
cases had associated significant CAD (15). Given the
unexpected and dynamic nature of cardiac arrest, it can be
difficult to establish whether or not acute myocardial isch-
emia was the precipitating event. Therefore, the lower
prevalence of previously diagnosed CAD in the normal LV
function group could indicate a higher prevalence of unrec-
ognized CAD, with SCD being the first and fatal manifes-
tation. Continued emphasis on reduction of established risk
factors for coronary artery disease is likely to remain valuable
for prevention of SCD (6,26).
There were other distinguishing features among patients
with normal LVEF (Table 1). Fourteen percent of subjects
had a known history of seizure disorder, and this condition
was found exclusively among subjects with normal LV
function. Sudden unexpected death in epilepsy (27–31)is
well recognized as a cause of death in patients with seizure
disorder. In population-based studies, increased seizure
frequency, duration of seizure disorder, and greater use of
anticonvulsant or psychotropic medications have all been
associated with this condition (29,32). With findings of
cardiac autonomic abnormalities (33) and of periods of
asystole in patients who were monitored during seizures
(34), a case has also been made for simultaneous and related
occurrence of seizures and heart rhythm disorders. Finally,
in a subgroup of patients with missed primary cardiac
arrhythmogenic disorders the clinical presentation of a
ventricular arrhythmia can mimic a seizure (35), which
remains a distinct possibility in the patient with ARVD and
seizure disorder in the present study. Overall, a higher
proportion of subjects with normal LV function were female
as well as younger in age. An earlier study from Albert et al.
(36) that evaluated gender differences among cardiac arrest
survivors, observed that females were less likely to have
CAD. However, the same study found that CAD status was
the most important predictor of cardiac arrest in women,
and LV dysfunction the most important predictor in men
(36). From a separate autopsy-based study, we have previ-
ously reported a higher rate of unexplained SCD among
younger women compared to men (37). In general, disease
conditions in younger age groups are more likely to have
genetic (as opposed to environmental) influences (38), and
the possibility exists that genetic factors may also contribute
to risk of SCD (39).
Study limitations. Because this study was dependent on
the performance of LV function evaluation before SCD, the
analysis was performed in a subgroup of total SCD cases. In
general, this is an inherent limitation of population-based
studies, especially in an investigation of SCD. In as many as
50% of cases, SCD can be the first manifestation of heart
disease. Although prospective cohorts can circumvent this
limitation, the numbers of subjects studied in existing
cardiovascular cohorts may yield limited numbers of SCD
cases per year. Nonetheless, in the present study, medical
records from emergency medicine responders or the medical
examiner were available in 98% of subjects, and LV function
evaluation was performed before SCD in a significant
subgroup. Because symptomatic patients with greater sever-
ity of pre-existing heart disease are more likely to have
LVEF evaluated, any bias in our results is likely to reflect an
overestimation of the prevalence of LV dysfunction among
SCD cases in the general population. Due to potential
demographic and socioeconomic differences between Mult-
nomah County and the rest of the country, caution should
be exercised in generalizing results of this study to other
communities with significantly different characteristics.
Conclusions. In this large U.S. subpopulation followed for
two years, approximately one-half of the SCD cases that
underwent evaluation before cardiac arrest had LV dysfunc-
tion, and one-third had severe LV dysfunction. Younger
age, female gender, seizure disorder, specific medications,
and lower likelihood of recognized CAD were identified as
distinguishing characteristics of patients with normal LV
systolic function and SCD. Left ventricular dysfunction is a
significant determinant of SCD risk in the general popula-
tion, but a renewed emphasis on identifying alternative
SCD risk predictors in the general population is warranted.
Acknowledgments
The authors would like to acknowledge the significant
contribution of American Medical Response, Portland/
Gresham fire departments, the Multnomah County Medi-
cal Examiner’s office and the emergency medicine, cardiol-
ogy, and primary care physicians and allied health personnel
of the 16 area hospitals. The authors thank Kyndaron
Reinier for her critical review of the manuscript.
Reprint requests and correspondence: Dr. Sumeet S. Chugh,
Cardiology Division, UHN-62, Oregon Health and Science Uni-
versity, 3181 SW Sam Jackson Park Road, Portland, Oregon
97239. E-mail: chughs@ohsu.edu.
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et al.
March 21, 2006:1161– 6
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Page 5
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JACC Vol. 47, No. 6, 2006
LV Dysfunction and Sudden Cardiac Death
March 21, 2006:1161– 6
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    • "Both the left ventricular dysfunction as the functional class (New York Heart Association) are important risk factors for SCD and were incorporated as clinical and diagnostics parameters that guide the implant of automatic implantable cardioverterdefibrillator (ICD) for primary prevention of SCD [16]. Most patients who experienced a cardiac arrest, however, does not have a left ventricular ejection fraction (LVEF) documented <35% before the SCD and therefore would not fulfill criteria for ICD implantation [17,18]. SCD, CKD, and epidemiology Initial studies demonstrate an increased risk of SCD in patients with kidney disease from clinical trial subgroup analyses to assess the effectiveness of ICDs. "
    [Show abstract] [Hide abstract] ABSTRACT: Several studies have shown a strong independent association between chronic kidney disease (CKD) and cardiovascular events, including death, heart failure, and myocardial infarction. Recent clinical trials extend this range of adverse cardiovascular events, also including ventricular arrhythmias and sudden cardiac death. Furthermore, other studies suggest structural remodeling of the heart and electrophysiological alterations in this population. These processes may explain the increased risk of arrhythmia in kidney disease and help to identify patients who are at increased risk of sudden cardiac death. Sympathetic hyperactivity is well known to increase cardiovascular risk in CKD patients and is a hallmark of essential hypertensive state that occurs early in the clinical course of the disease. In CKD, the sympathetic hyperactivity seems to be expressed at the earliest clinical stage of the disease, showing a direct relationship with the severity of the condition of renal failure, being more pronounced in the terminal stage of CKD. The sympathetic efferent and afferent neural activity in kidney failure is a key mediator for the maintenance and progression of the disease. The aim of this review was to show that the feedback loop of this cycle, due to adrenergic hyperactivity, also aggravates many of the risk factors responsible for causing sudden cardiac death and may be a potential target modifiable by percutaneous renal sympathetic denervation. If it is feasible and effective in end-stage renal disease, little is known.
    Full-text · Article · Dec 2015
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    • "The slight difference in the average accuracy and AUC is due to the difference in selected feature set for Experiment 1 (1, 4, 5, 6, 15, 16, 17) and Experiment 2, where the feature set can be different for each fold. The method used on all the training data provides the set: (1, 2, 3, 4, 11, 17). Similarly, the SVM classifier with a third order polynomial kernel without SMOTE gave an average AUC of 0.776 and 0.921 for Experiment 1 and Experiment 2, respectively. "
    [Show abstract] [Hide abstract] ABSTRACT: Introduction: Patients surviving myocardial infarction (MI) can be divided into high and low arrhythmic risk groups. Distinguishing between these two groups is of crucial importance since the high-risk group has been shown to benefit from implantable cardioverter defibrillator insertion; a costly surgical procedure with potential complications and no proven advantages for the low-risk group. Currently, markers such as left ventricular ejection fraction and myocardial scar size are used to evaluate arrhythmic risk. Methods: In this paper, we propose quantitative discriminative features extracted from late gadolinium enhanced cardiac magnetic resonance images of post-MI patients, to distinguish between 20 high-risk and 34 low-risk patients. These features include size, location, and textural information concerning the scarred myocardium. To evaluate the discriminative power of the proposed features, we used several built-in classification schemes from matrix laboratory (MATLAB) and Waikato environment for knowledge analysis (WEKA) software, including k-nearest neighbor (k-NN), support vector machine (SVM), decision tree, and random forest. Results: In Experiment 1, the leave-one-out cross-validation scheme is implemented in MATLAB to classify high- and low-risk groups with a classification accuracy of 94.44%, and an AUC of 0.965 for a feature combination that captures size, location and heterogeneity of the scar. In Experiment 2 with the help of WEKA, nested cross-validation is performed with k-NN, SVM, adjusting decision tree and random forest classifiers to differentiate high-risk and low-risk patients. SVM classifier provided average accuracy of 92.6%, and AUC of 0.921 for a feature combination capturing location and heterogeneity of the scar. Experiment 1 and Experiment 2 show that textural features from the scar are important for classification and that localization features provide an additional benefit. Conclusion: These promising results suggest that the discriminative features introduced in this paper can be used by medical professionals, or in automatic decision support systems, along with the recognized risk markers, to improve arrhythmic risk stratification in post-MI patients.
    Full-text · Article · Jul 2015 · Artificial intelligence in medicine
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    • "These malignant arrhythmias can be terminated by implantable cardioverter-defibrillator (ICD) therapy. Currently, poor left ventricular ejection fraction (LVEF) is the primary index that is used to decide whether or not to implant an ICD123456. However, many patients with poor LVEF may not benefit from the ICD implantation as the annual firing rates are approximately 5% [1,5] . "
    [Show abstract] [Hide abstract] ABSTRACT: Myocardial infarct heterogeneity indices including peri-infarct gray zone are predictors for spontaneous ventricular arrhythmias events after ICD implantation in patients with ischemic heart disease. In this study we hypothesize that the extent of peri-infarct gray zone and papillary muscle infarct scores determined by a new multi-contrast late enhancement (MCLE) method may predict appropriate ICD therapy in patients with ischemic heart disease. The cardiovascular magnetic resonance (CMR) protocol included LV functional parameter assessment and late gadolinium enhancement (LGE) CMR using the conventional method and MCLE post-contrast. The proportion of peri-infarct gray zone, core infarct, total infarct relative to LV myocardium mass, papillary muscle infarct scores, and LV functional parameters were statistically compared between groups with and without appropriate ICD therapy during follow-up. Twenty-five patients with prior myocardial infarct for planned ICD implantation (age 64+/-10 yrs, 88% men, average LVEF 26.2+/-10.4%) were enrolled. All patients completed the CMR protocol and 6--46 months follow-up at the ICD clinic. Twelve patients had at least one appropriate ICD therapy for ventricular arrhythmias at follow-up. Only the proportion of gray zone measured with MCLE and papillary muscle infarct scores demonstrated a statistically significant difference (P < 0.05) between patients with and without appropriate ICD therapy for ventricular arrhythmias; other CMR derived parameters such as LVEF, core infarct and total infarct did not show a statistically significant difference between these two groups. Peri-infarct gray zone measurement using MCLE, compared to using conventional LGE-CMR, might be more sensitive in predicting appropriate ICD therapy for ventricular arrhythmia events. Papillary muscle infarct scores might have a specific role for predicting appropriate ICD therapy although the exact mechanism needs further investigation.
    Full-text · Article · Jun 2013 · Journal of Cardiovascular Magnetic Resonance
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