Incidence and Prognostic Value of Early Repolarization Pattern in the 12-Lead
Electrocardiogram
Daisuke Haruta, Kiyotaka Matsuo, Akira Tsuneto, Shinichiro Ichimaru, Ayumi Hida, Nobuko
Sera, Misa Imaizumi, Eiji Nakashima, Koji Maemura and Masazumi Akahoshi
Circulation. 2011;123:2931-2937; originally published online June 6, 2011;
doi: 10.1161/CIRCULATIONAHA.110.006460
Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 2011 American Heart Association, Inc. All rights reserved.
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Incidence and Prognostic Value of Early Repolarization
Pattern in the 12-Lead Electrocardiogram
Daisuke Haruta, MD, PhD; Kiyotaka Matsuo, MD, PhD; Akira Tsuneto, MD, PhD;
Shinichiro Ichimaru, MS; Ayumi Hida, MD, PhD; Nobuko Sera, MD, PhD; Misa Imaizumi, MD, PhD;
Eiji Nakashima, PhD; Koji Maemura, MD, PhD; Masazumi Akahoshi, MD, PhD
Background—Early repolarization pattern is a common ECG finding characterized by J-point elevation and QRS notching or slurringin the inferior and/or lateral leads, yet little is known about its incidence and long-term prognosis in Asian populations.
Methods and Results—We reviewed all the ECG records of the 5976 atomic-bomb survivors who were examined at least once
during our biennial health examination in Nagasaki, Japan, between July 1958 and December 2004. We defined early
repolarization pattern as ⱖ0.1-mV elevation of the J point or ST segment, with notching or slurring in at least 2 inferior and/or
lateral leads. We assessed unexpected, cardiac, and all-cause death risk by Cox analysis. We identified 1429 early repolarization
pattern cases (779 incident cases) during follow-up, yielding a positive rate of 23.9% and an incidence rate of 715 per 100 000
person-years. Early repolarization pattern had an elevated risk of unexpected death (hazard ratio, 1.83; 95% confidence interval, 1.12
to 2.97; P⫽0.02) and a decreased risk of cardiac (hazard ratio, 0.75; 95% confidence interval, 0.60 to 0.93; P⬍0.01) and all-cause(hazard ratio, 0.85; 95% confidence interval, 0.78 to 0.93; P⬍0.01) death. In addition, both slurring and notching were related tohigher risk of unexpected death (hazard ratio, 2.09; 95% confidence interval, 1.06 to 4.12; P⫽0.03), as was early repolarization
pattern manifestation in both inferior and lateral leads (hazard ratio, 2.50; 95% confidence interval, 1.29 to 4.83; P⬍0.01).
Conclusions—Early repolarization pattern is associated with an elevated risk of unexpected death and a decreased risk ofcardiac and all-cause death. Specific early repolarization pattern morphologies and location are associated with anadverse prognosis. (Circulation. 2011;123:2931-2937.)
Key Words: death, sudden 䡲 epidemiology 䡲 electrocardiography 䡲 mortalitySudden cardiac death is a major health issue, and accounts for
300 000 to 400 000 deaths per year in the United States.1,2Coronary artery disease, cardiomyopathy, left ventricular hypertrophy, valvular disease, congenital heart disease, and primaryelectrophysiological abnormalities are the major causes of sudden cardiac death.1,2 Approximately 5% of sudden cardiac
deaths caused by ventricular tachyarrhythmias occur in theabsence of structural heart or coronary artery disease and are
attributable to primary electrophysiological abnormalities. Somecases with ventricular tachyarrhythmia show a characteristic12-lead ECG pattern such as a long-QT interval (long-QT
syndrome) and a coved-type ST-segment elevation in the rightprecordial leads (V1, V2, and V3; Brugada syndrome).3,4

Clinical Perspective on p 2937
Early repolarization pattern (ERP) is characterized by anelevation of the QRS-ST junction (J point) and QRS notchingor slurring (J wave) in multiple leads, especially in the inferior
and/or left precordial leads, and is found in a relatively large

proportion (1% to 13%) in previous reports.5– 8 Although conventionally considered benign,5 it is potentially arrhythmogenic,9 and in 2 clinical case-control studies, patients with ahistory of idiopathic ventricular fibrillation (VF) showed anincreased prevalence of ERP.7,8 It has recently been reported that
ERP in the inferior leads is associated with increased risk ofcardiac death in Western populations.10 Not much is known,
however, about the incidence and long-term prognosis of ERP in
Asian populations. Thus, we prospectively examined the incidence and prognostic value of ERP in terms of unexpected
death, cardiac death, and all-cause death in Nagasaki Adult
Health Study (AHS) subjects.

Methods
General Procedures
Since July 1, 1958, 7564 atomic-bomb survivors (3374 men) in
Nagasaki, Japan, have been invited to participate in biennial healthexaminations as part of a follow-up program conducted by the
Radiation Effects Research Foundation (RERF). Detailed descriptions of the program have been published elsewhere.11,12 Each

Received November 9, 2010; accepted April 29, 2011.
From the Department of Cardiovascular Medicine, Course of Medical and Dental Sciences, Graduate School of Biomedical Sciences, Nagasaki
University, Nagasaki (D.H., K. Matsuo, A.T., K. Maemura); Department of Clinical Studies, Radiation Effects Research Foundation, Nagasaki (D.H.,
A.T., S.I., A.H., N.S., M.I., M.A.); Department of Statistics, Radiation Effects Research Foundation, Hiroshima (E.N.); and Saikakai Shibatachokodo
Hospital, Shimabara (D.H., K. Matsuo), Japan.
Correspondence to Daisuke Haruta, MD, Department of Clinical Studies, Radiation Effects Research Foundation, 1-8-6 Nakagawa, Nagasaki 850-0013,
Japan. E-mail harutad@rerf.or.jp© 2011 American Heart Association, Inc.
Circulation is available at http://circ.ahajournals.org

DOI: 10.1161/CIRCULATIONAHA.110.006460

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June 28, 2011

Figure 1. Twelve-lead ECG of a typical
pattern of the early repolarization pattern.
A slurring morphology is seen in the inferior leads (II, III, aVF), and a notching morphology is seen in leads V4 through V6
with ⱖ0.1-mV elevation from baseline. In
our grouping method, this case is classified as both notching and slurring in morphology and as both inferior and lateralleads in lead location, respectively.

examination includes a standard 12-lead ECG obtained by theregular procedure. We extracted 5976 subjects (2612 men) who had
been examined at least once between July 1, 1958, and December 31,
2004, and did not have intraventricular conduction disturbances andpacemaker implantation at the first examination and reviewed all the
ECG records (12.2⫾7.5 ECG records per subject) obtained during
the follow-up period. The mean length of follow-up for ECG
recordings was 23.6⫾14.7 years. The date of the first examination isdifferent for each individual. During the first 2 years from July 1,
1958, to June 30, 1960, 2912 subjects underwent examination; theremaining 3064 subjects underwent their first examination after that
period. We treated subjects who already had ERP at their firstexamination regardless of the date of examination as prevalent casesand subjects who first showed ERP after their second examination as
incident cases. We used the current dosimetry System DS02 to
estimate the bone marrow atomic-bomb radiation doses of individual
subjects.13 The Research Protocol Review and Human Investigation
Committees of RERF approved the protocol (RP A 14 – 08).

(50 with ERP and 150 without ERP) who were randomly selectedfrom the 5976 subjects. The concordance rate was 86.0% for ERP
diagnosis. Next, he blindly reviewed all the ECG records obtained
during follow-up for 194 subjects (94 subjects with only slurring ineither inferior or lateral lead and 100 subjects with only notching ineither inferior or lateral lead) among the 1429 subjects diagnosed ashaving ERP by the first cardiologist. The concordance rate was
83.8% for lead location and 81.3% for morphology.
In the diagnostic criteria of Brugada syndrome by consensus
reports,14,15 type 1 characterized by ⱖ0.2-mV coved-type ST segment elevation is essential, whereas types 2 and 3 characterized bysaddleback-type ST elevation are not.14,15 Therefore, in this study,
we defined subjects with type 1 characterized by ⱖ0.2-mV covedtype ST-segment elevation in ⱖ1 right precordial leads (V1 throughV3) at least once during follow-up as Brugada-type ECG cases.

Definition and Confirmation of Early
Repolarization Pattern andBrugada-Type Electrocardiogram

The RERF followed the vital status of all participants using Japan’sfamily registration system. We collected all of the death certificatesfrom July 1958 to December 2004 to check the cause and circumstanceof death for deceased subjects and defined 3 types of death as we did in
our Brugada-type ECG study: sudden death, an out-of-hospital deathoccurring within 1 hour of the onset of acute symptoms; unexplained
accidental death, an accidental death in which VF might have been thecause of the accident; and unexpected death, a sudden death or an
unexplained accidental death.16 We treated death resulting from congestive heart failure and ischemic heart disease as cardiac death.

Using criteria similar to those of Haı̈ssaguerre and colleagues,7 wedefined ERP cases as having (1) an elevation of the QRS-ST junction(J point) in notching formation (positive J deflection inscribed on the
S wave) or of the ST segment in slurring formation (smoothtransition from QRS complex to the ST segment) in at least 2 leadsand (2) an amplitude of QRS-ST junction (J point) or ST-segment
elevation ⱖ0.1 mV above the baseline as QRS notching or slurringin the inferior leads (II, III, aVF), lateral leads (I, aVL, V4 throughV6), or both7 (Figure 1) at least once during follow-up. In slurringformation, because the transition from QRS complex to ST segment
is smooth or the J point may be hidden in the QRS complex, we used
ⱖ0.1 mV of the ST-segment elevation to indicate high-takeoff
QRS-ST junction as the criterion. We classified the time course of
the J-point abnormality into 1 of 2 categories: a persistent course
showing permanent abnormalities or an intermittent course showing
transient disappearance of the J wave itself or normalization of themagnitude of the J point during follow-up (Figure 2). Duringfollow-up, we classified cases by positive-ERP lead location (inferior, lateral, or both) and by J-wave morphology (notching, slurring,or both). We defined the onset of ERP as the date of its first
appearance during follow-up and used the age at the onset of ERP
in calculating the incidence. One cardiologist (D.H.) reviewed the12-lead ECGs of all subjects without knowledge of the clinicaldiagnosis or death certificate information. A second cardiologist(K. Matsuo) blindly reviewed all the ECG records of 200 subjects

Definition and Confirmation of Sudden Death,
Unexplained Accidental Death, and Cardiac Death

Statistical Analysis
We calculated the 46.5-year (July 1, 1958, to December 31, 2004)
incidence on the basis of the age of incident cases at ERP appearance by
a person-year method, stratified according to age. We used Cox
regression analysis to assess the long-term prognosis of ERP and
Brugada-type ECG cases after controlling for age and sex. We compared ERP and Brugada-type ECG cases with control subjects who hadneither ERP nor Brugada-type ECG with respect to unexpected death,cardiac death, and death resulting from all causes. We also assessed
unexpected death risk according to lead location and J-wave morphology in ERP cases. Survival time is the time from the date of the firstexamination for controls and prevalent ERP and Brugada-type ECG
cases and the date of the first appearance for incident ERP and
Brugada-type ECG cases to the date of death or December 31, 2004,
whichever came first. All analyses were conducted with SAS for UNIX(SAS Institute, Cary, NC).17 We expressed the data as mean⫾SD andconsidered P⬍0.05 to be statistically significant.

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Haruta et al

The Epidemiology of Early Repolarization

2933

Figure 2. Time course of the ECG (inferior and left precordial leads) in a case of unexpected death in a man. We observed early repolarization pattern with slurring in inferior leads (II, III, aVF) and notching in left precordial leads V4 through V6 with ⱖ0.1-mV elevationfrom baseline at the first visit in 1960. At the follow-up, the J-wave morphology was consistent in the inferior leads, but the magnitude
of ST elevation fluctuated, whereas in the left precordial leads, both the morphology (slurring and notching) and J-point magnitude fluctuated during follow-up. In 1984, the patient died of sudden death at home at 71 years of age.

the sexes, whereas the male preponderance became obvious
thereafter, leading to twice as high an overall incidence for men(Table 1). Radiation dose was not associated with ERP in bothprevalent and incident cases (P⫽0.89, data not shown).
We identified 30 Brugada-type ECG cases (see Table 2).
Brugada-type ECGs showed a J-point elevation in the anterior precordial leads. Among them, 6 cases had both ERP and
Brugada-type ECG (Figure 3).

Results
Incidence of Early Repolarization Pattern
We identified 1429 ERP cases (815 men) among 5976 AHS
subjects during the whole study period (July 1, 1958, toDecember 31, 2004); 650 cases (413 men) were classified asprevalent cases and 779 cases (402 men) were classified asincident cases (mean⫾SD age at first appearance of ERP,
47.2⫾15.4 years), yielding a follow-up positive rate of 23.9%(1429 of 5976) and an incidence of 715 per 100 000 personyears (Table 1). Incidence was highest in the second decadeof life for men and women and was almost identical between

Lead Location and Morphology of the J Wave
Table 3 shows the morphology and lead location of the J
wave observed during the follow-up period. Almost all of theTable 1. Number of Subjects at the First Examination for Each Individual and Incidence From July 1958
to December 2004
Subjects, n

Incident ERP
Cases, nPerson-Years*

Incidence, n/100 000
Person-yAge, y

Men

Women

Men

Women

Men

Women

Men

Women

ⱕ19
20 –29
30–39
40–49
50–59
60–69
70–79
ⱖ80
Total

160
432
609
492
533
296
80
10
2612

155
551
1250
598
478
236
78
18
3364

287
1798
5434
7009
9199
8718
4810
1292
38 547358
2532
10 02414 811
16 57314 7248858
2587
70 467

9
38
96
71
75
79
29
5
402

12
41
103
77
59
59
24
2
377

3136
2113
1767
1013
815
906
603
387
1043

3352
1619
1028
520
356
401
271
77
535

5976

109 014779

715

ERP indicates early repolarization pattern.
*Aggregate numbers of years contributed to each age category from 1958 to 2004 by all subjects remaining at risk for ERP.

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Table 2. Cause of Mortality in Subjects With Early
Repolarization Pattern, Brugada-Type ECG, and Neither Early
Repolarization Pattern nor Brugada-Type ECG

Table 3. Lead Location and Morphology of the J Wave During
Follow-Up Among Subjects With Early Repolarization Pattern
Morphology, n patients

Cause of Death

ERP (with Brugada-type ECG)
Brugada-type ECG without
ERP
Neither ERP nor Brugada-type
ECG
Total

Subjects, nAll

Unexpected

Cardiac1429 (6)24628 (4)14

27 (0)
4

100 (0)
1

4523

2262

45

434

5976

2904

76

535

Lead location
Inferior
LateralInferior andlateral
Total

Notching

Slurring

Notching and Slurring

Total

337
335
141

44
54
50

41
172
255

422
561
446

813

148

468

1429

ERP indicates early repolarization pattern.

ERP cases (98.3%) showed intermittent manifestations, andboth characteristics changed over time (Figure 2).

Mortality From Unexpected Death, Cardiac Death,and All-Cause Death
Table 2 shows the breakdown of the 5976 subjects into ECG
category and their cause of death. The 27 ERP cases with orwithout Brugada-type ECG (19 men; age at death, 68.6⫾19.1
years; age range, 20.7 to 96.1 years), 4 Brugada-type ECG cases
without ERP (3 men; age at death, 59.5⫾12.4 years; age range,
42.3 to 71.7 years), and 45 controls (23 men; age at death,65.6⫾16.3 years; age range; 24.2 to 95.8 years) had unexpected
death. Age at unexpected death was not different among the 3groups. The time interval between the first ECG appearance of
ERP and unexpected death based on 16 incident ERP cases was
21.7⫾13.8 years (range, 2.5 to 42.3 years). In Cox proportional
hazards analysis, ERP predicted unexpected death (hazard ratio[HR], 1.83; 95% confidence interval [CI], 1.12 to 2.97; P⫽0.02)
and had a favorable effect on cardiac (HR, 0.75; 95% CI, 0.60 to
0.93; P⬍0.01) and all-cause (HR, 0.85; 95% CI, 0.78 to 0.93;
P⬍0.01) death (Table 4).
With respect to lead location and J-wave morphology, ERP
cases with a broad range of J-wave–positive leads (bothinferior and lateral) had a significantly higher HR for unexpected death (HR, 2.50; 95% CI, 1.29 to 4.83; P⬍0.01) andboth slurring and notching predicted unexpected death (HR,2.09; 95% CI, 1.06 to 4.12; P⫽0.03) when we used controls
as the reference group (Table 4). We saw no unexpected
deaths for patients with ERP with Brugada-type ECG and so
could not calculate that HR for unexpected death.
Brugada-type ECG cases had the highest HR for unexpected
death (HR, 27.15; 95% CI, 9.35 to 78.85; P⬍0.01), whereas incontrast to ERP cases, it had no favorable effects on cardiac andall-cause death (Table 4). Radiation dose was not associated with
unexpected death (P⫽0.45; data not shown).

Discussion
As far as we know, this 5-decade study is the first Asian
population– based study of the incidence and prognosis of
ERP. We learned that ERP was a common ECG finding, witha follow-up positive rate of 23.9% and an incidence of 715 in
100 000 person-years, and was associated with a higher riskof unexpected death and a lower risk of cardiac and all-cause
death. Although the subjects were atomic-bomb survivors,
radiation dose was not associated with ERP or unexpected
death, so the results should be generalizable.

Incidence of Early Repolarization Pattern
The prevalence of ERP has been reported to be 1% to 13%.5– 8
However, because ERP (defined by the modified criteria ofHaı̈ssaguerre and colleagues7) appeared intermittently, we based

Figure 3. A case with both early repolarization pattern and Brugada-type ECG inchest leads V1 through V6. Coved-type ST
elevation with 0.2 mV at the J point wasseen in V1 and V2, and early repolarization
pattern with notching morphology 0.1 mV
at the J point was seen in V4 through V6.
Coved-type ST elevation of Brugada-type
ECG (V1 and V2) and notching morphology of early repolarization pattern (V4through V6) at the last recorded beat arehighlighted by circles.

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Haruta et al
Table 4.

The Epidemiology of Early Repolarization

2935

Age- and Sex-Adjusted Hazard Ratio for Each Group (Cox Analysis)
HR (95% CI)

Control*
ERP
P
Lead location
Inferior
P
LateralP
BothP
Morphology
Notching
P
Slurring
P
BothP
Brugada-type ECG

Subjects, n

Unexpected Deaths, n

Unexpected Death

Cardiac Death

All-Cause Death

4523
1429

45
27

1.00
1.83 (1.12–2.97)
0.02

1.00
0.75 (0.60–0.93)
⬍0.01

1.00
0.85 (0.78–0.93)
⬍0.01

422

8

561

7

446

12

1.91 (0.88–4.14)
0.10
1.37 (0.61–3.04)
0.45
2.50 (1.29–4.83)
⬍0.01

813

11

148

5

468

11

24

4

0.47 (0.07–3.35)

1.09 (0.65–1.85)

0.45

0.74

⬍0.01

P
Total

1.36 (0.70–2.65)
0.37
1.60 (0.61–4.24)
0.34
2.09 (1.06–4.12)
0.03
27.15 (9.35–78.85)

5976

76

HR indicates hazard ratio; CI, confidence interval; and ERP, early repolarization pattern.
*Subjects with neither ERP nor Brugada-type ECG.

our calculation on both prevalent and incident cases and foundthat 23.9% manifested ERP at least once during follow-up,
indicating that ERP was not a rare ECG finding. In past studies,
only the prevalence, not incidence, of ERP has been reported
because longitudinal studies covering the period before thediagnosis of ERP were lacking. We report the incidence of ERP
for the first time here and reveal that the incidence of ERP was
highest in the second decade of life in men and women anddecreased thereafter (Table 1). It is possible that the difference inthe age distribution of the subjects in the target cohort and theintermittent appearance of ERP may have affected the reported
prevalence of ERP. It is also possible that if we used criteriaother than the modified criteria of Haı̈ssaguerre and colleagues,
we would have found different incidence values.
The incidence of ERP that we observed (Table 1) was ⬇50
times as high as the incidence reported for Brugada-type ECG(14.3/100 000 person-years),16 whereas the male/female incidence ratio for ERP (1.95) was about one-fifth that of
Brugada-type ECG (8.97),16 but the incidence of both ERP
and Brugada-type ECG is high at a relatively young age.
Because our cohort of atomic-bomb survivors did not include
subjects who were ⬍12 years of age on July 1, 1958, and theappearance of ERP was intermittent, it is necessary to follow
up a large number of the population who are ⬍10 years of age
to arrive at a more precise value.

Prognostic Value of Early Repolarization Pattern
Sinner et al18 recently reported in a prospective cohort study
that ERP was associated with a ⬇2- to 4-fold increased riskof cardiac mortality, which was determined through the use ofdeath certificates. They did not mention the association

between ERP and unexpected death because cardiac death
was assumed in the ninth version of the International Classification of Diseases codes 390 to 429 and 798.18 On theother hand, Haı̈ssaguerre et al7 reported that ERP in theinferior or lateral leads was more frequent among patientswith idiopathic VF than among control subjects. Rosso et al8
reported a similar association between ERP and idiopathic
VF. Those studies were cross-sectional; here, in a prospective
cohort study, ERP predicted unexpected death. How ERP did
that, however, is unclear. It has been reported that 11% of
Brugada syndrome patients show ERP in the inferior-lateralleads and that drug challenge tests provoke a coved pattern in
the inferior-lateral leads in 4.6% of Brugada syndrome
patients.19 Those observations suggest that ERP and Brugada
syndrome overlap in phenotype and electrophysiologicalsimilarities. The presence of a prominent Ito-mediated action
potential notch (spike and dome) in the epicardium, but not theendocardium, generates a transmural voltage gradient during theearly phase of repolarization, which manifests J-wave andJ-point elevation in the surface ECG in both ERP and Brugada
syndrome.20 Heterogeneous loss of the action potential dome
produces phase 2 reentry, leading to polymorphic ventriculartachycardia/VF.20 It is possible that ERP has a vulnerability toarrhythmias that is due to transmural heterogeneity of ventricularrepolarization and that ERP is affected by such factors as
testosterone and drugs through ion channel activity.
A J-wave manifestation in both inferior and lateral leads
was associated with a higher risk of unexpected death. A
J-wave manifestation in many leads suggested that electric
instability caused by heterogeneity of repolarization was
occurring in broad regions of the ventricles. Merchant et al21

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June 28, 2011

reported that notching in lateral leads is significantly moreprevalent among ERP patients with idiopathic VF, but they
did not assess morphological changes over time. In our study,
we defined slurring, notching, and slurring and notching,taking morphological changes into account during follow-up,
and found that manifestation in both slurring and notchinghas an important implication for risk stratification.
In this study, ERP cases had a lower risk of cardiac andall-cause mortality. On the other hand, it has also beenreported that ERP in the inferior leads is associated with anincreased risk of cardiac death, (HR, 1.28; 95% CI, 1.04 to
1.59; P⫽ 0.03),10 and ERP in any localization was associatedwith an increased risk of all-cause death (HR, 1.87; 95% CI,
1.03 to 3.37; P⫽0.038).18 Thus, the association between ERP
and mortality other than unexpected death is still controversial. We proposed a hypothesis that testosterone may modulate cardiac and total mortality in ERP cases. Various reports
indicate that testosterone may be associated with ERP and
Brugada syndrome. Early repolarization pattern showed male
preponderance7,8,10; the typical coved-type Brugada ECG
disappears after surgical castration for prostate cancer22; andmale Brugada syndrome cases have significantly higher
plasma testosterone levels than age-matched male controls.23
It has been suggested that testosterone may increase theoutward repolarizing potassium currents such as IK1, IKr, IKs
and Ito, inhibiting inward L-type Ca2⫹ current.24 –26 Sucheffects help to induce an outward shift of current in theepicardium, aggravate transmural voltage gradient between epicardium and endocardium, and lead to the J-point and ST-segment
elevation seen in ERP and Brugada syndrome. These reportssuggest that testosterone is associated with ERP and Brugada
syndrome through ion channel activity. On the other hand, several
studies reported that low serum testosterone level was associatedwith an increased risk of cardiovascular and all-cause mortality andcardiovascular risk factors in men (abnormal lipid profiles, impaired
glucose metabolism, and high blood pressure).27–29 Thus, elevatedserum testosterone level may influence the prognosis of patientswith ERP by increasing the risk of sudden death through a more
prominent transmural voltage gradient, which leads to phase 2
reentry and ventricular tachycardia/VF, while decreasing the risk ofcardiac and all-cause death, probably through protective effects.
However, this hypothesis should be supported by more direct
evidence of the association between testosterone and ERP.
In the present study, the HR for unexpected death was lower
for ERP (1.83) than for Brugada-type ECG (27.15), and may notdirectly lead to the recommendation of implantable cardioverterdefibrillator treatment. However, because the number of ERP
cases (1429) was much larger than the number of Brugada-type
ECG cases (24), the unexpected death rate was greater for ERP
cases (27 of 76, 35.5%) than for Brugada-type ECG cases (4 of76, 5.3%), suggesting a greater public health implication for
ERP and a careful evaluation of the past history of syncope andthe family history of sudden death or syncope. Further epidemiological and electrophysiological studies are needed to clarify
what characteristics among the large number of ERP cases are
predictive of high risk.

Study Limitations
In this study, only 1 cardiologist reviewed all the ECG records
obtained during follow-up in 5976 subjects. However, theaccuracy of the diagnosis was ensured because all the ECG
records (12.2⫾7.5 ECG records per subjects) during follow-up
were reviewed for each subject. A second cardiologist blindly
reviewed all the ECG records obtained during follow-up in 200
subjects (50 with ERP and 150 without ERP) and 194 ERP
cases, and the concordance rate was 86.0% for ERP diagnosis,
83.8% for lead location, and 81.3% for morphology.
We could not deny the effect of structural heart diseases on
ERP because we did not perform echocardiography andcardiac catheterization in this epidemiological study.
We did not assess the risk of unexpected death by thenature of the manifestation of ERP (intermittent/persistent),
because almost all of the ERP cases (98.3%) showed theintermittent course. Because the magnitude of the J point
fluctuated over time in ERP cases, the most elevated values ofJ point were biased, depending on how many times the ECG
was recorded. Thus, we did not assess the effects of themagnitude of J point on unexpected death. For the same reason,other ECG characteristics such as QRS duration and QTcinterval were not used as covariates in Cox regression analysis.
With respect to Brugada-type ECG, we did not include 10
patients with types 2 and 3 in the Brugada-type ECG group.
We cannot deny the possibility that they might have changed
into type 1 if they had drug challenge tests, which could not
be performed in our cohort study. We observed 3 unexpected
deaths among 10 patients with types 2 and 3.
Age at unexpected death was relatively high in both ERP
cases and controls. Uncertainty of the cause of sudden or
unexplained accidental death without autopsy information, especially for coronary heart disease, may limit the present results,
but this possible bias would be equal for ERP cases and controls.
Because the number of unexpected deaths in ERP cases by leadlocation and morphology subgroup and in Brugada-type ECG cases
was small, such data might limit efforts to draw a definitive
conclusion about effects of ERP by lead location and morphology
subgroup and Brugada-type ECG on unexpected death.

Conclusions
In this 5-decade population-based study, we described theepidemiology and long-term prognosis of ERP. Early repolarization pattern was a common ECG finding; ERP appearedintermittently, and its location and J-wave morphology changed
over time. Early repolarization pattern was associated with anelevated risk of unexpected death and a decreased risk of cardiac
and all-cause death. The manifestation of both slurring andnotching and the manifestation of the J wave in both inferior andlateral leads were associated with the higher risk of unexpected
death. Further clinical and experimental studies are needed todefine the characteristics of high-risk ERP cases so that they canbe singled out for preventive measures.

Acknowledgments
We thank Tomohiro Ikeda for his help in preparation of themanuscript and Dr Miriam Bloom (SciWrite Biomedical Writing &Editing Services) for professional editing.

Sources of Funding
The RERF in Hiroshima and Nagasaki, Japan, is a private, nonprofit
foundation funded by the Japanese Ministry of Health, Labour and

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Haruta et al
Welfare and the US Department of Energy, the latter through the
National Academy of Sciences.

Disclosures
None.

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CLINICAL PERSPECTIVE
Recent studies have suggested a potential arrhythmogenicity and a higher risk of cardiac or all-cause death of early repolarization
pattern (ERP) in Western populations. But, the incidence and prognosis of ERP in an Asian population have not yet been
elucidated. We investigated 5976 atomic-bomb survivors followed up for ⬇5 decades. Early repolarization pattern was a very
common finding throughout the survivors’ entire lives, yielding a lifetime positive rate of 23.9%, an incidence rate of 715 per
100 000, and male predominance. In this study, ERP patients had an increased risk of unexpected death and a decreased risk ofcardiac and all-cause death. The ERP manifestation of both slurring and notching and the manifestation of the J wave in broad
leads were associated with unexpected death. The hazard ratio for unexpected death in ERP was lower than that in Brugada-type
ECG. However, because ERP is a very common finding, ERP has a greater public health implication.

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