The Early Repolarization Pattern · The term early repolarization has been in use for more than 50 years. This electrocardiographic pattern was considered benign until 2008, when

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THE PRESENT AND FUTURE

REVIEW TOPIC OF THE WEEK

The Early Repolarization Pattern

Peter W. Macfarlane, DSC,* Charles Antzelevitch, PHD,y Michel Haissaguerre, MD,z Heikki V. Huikuri, MD, PHD,xMark Potse, PHD,k Raphael Rosso, MD,{ Frederic Sacher, MD,z Jani T. Tikkanen, MD, PHD,x Hein Wellens, MD,#Gan-Xin Yan, MD, PHD**

ABSTRACT

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The term early repolarization has been in use for more than 50 years. This electrocardiographic pattern was considered

benign until 2008, when it was linked to sudden cardiac arrest due to idiopathic ventricular fibrillation. Much confusion

over the definition of early repolarization followed. Thus, the objective of this paper was to prepare an agreed definition

to facilitate future research in this area. The different definitions of the early repolarization pattern were reviewed to

delineate the electrocardiographic measures to be used when defining this pattern. An agreed definition has been

established, which requires the peak of an end-QRS notch and/or the onset of an end-QRS slur as a measure, denoted Jp,

to be determined when an interpretation of early repolarization is being considered. One condition for early repolarization

to be present is Jp $0.1 mV, while ST-segment elevation is not a required criterion. (J Am Coll Cardiol 2015;66:470–7)

© 2015 by the American College of Cardiology Foundation.

T he electrocardiographic (ECG) pattern ofearly repolarization has historically beenregarded as a benign ECG variant. However,

during the past few years, this concept has been chal-lenged on the basis of multiple reports linking theearly repolarization pattern in the inferior and/orlateral leads of the standard 12-lead ECG with anincreased risk for sudden cardiac death (1,2). Case-control studies have unanimously shown that pa-tients resuscitated from cardiac arrest of unknownetiology have a higher prevalence of the ECG patternof early repolarization in the inferior and/or lateralleads (i.e., the early repolarization syndrome) thanmatched control subjects. Epidemiological follow-upstudies have also shown that the early repolarizationpattern carries an increased risk for future arrhythmic

m the *Institute of Cardiovascular and Medical Sciences, Electrocardiolo

gdom; yCardiovascular Research Program, Lankenau Institute for Medic

iversity Hospital, LIRYC Institute, INSERM 1045, Bordeaux University, Bor

iversity Central Hospital, and University of Oulu, Oulu, Finland; kInriael Aviv Sourasky Medical Center, Tel Aviv, Israel; #Department of Cardio

**Lankenau Institute for Medical Research, Wynnewood, Pennsylvania

ionships relevant to the contents of this paper to disclose.

ten to this manuscript’s audio summary by JACC Editor-in-Chief Dr. Vale

nuscript received February 5, 2015; revised manuscript received April 21,

death (3,4). Therefore, the recognition and correctdiagnosis of the ECG pattern of early repolarizationhas importance for specialists, general cardiologists,and physicians.

The ECG term early repolarization has been in useby cardiologists for almost 40 years. Its exact defini-tion has varied according to different investigators,so much so that a recent review (5) showed thatthe prevalence of early repolarization apparentlyvaried between 2% and 31%. One definition of earlyrepolarization, published in 1976 by Kambara andPhillips (6), which built on earlier work by Wasser-burger and Alt (7), suggested that early repolarizationwas defined by: 1) end-QRS notching or slurring;2) elevation of the ST-segment; and 3) an upward-sloping ST-segment followed by a tall, symmetrical

gy Section, University of Glasgow, Glasgow, United

al Research, Wynnewood, Pennsylvania; zBordeauxdeaux, France; xMedical Research Center Oulu, Oulu

Bordeaux Sud-Ouest, 33405 Talence cedex, France;

logy, University of Maastricht, the Netherlands; and

. The authors have reported that they have no re-

ntin Fuster.

2015, accepted May 18, 2015.

AB BR E V I A T I O N S

AND ACRONYM S

ECG = electrocardiography

Jo = J onset

Jp = J peak

J termination

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T-wave. However, many cardiologists have reportedthe presence of ST-segment elevation alone, mostcommonly in the inferior and lateral leads in youngerpersons, as being consistent with early repolarization.This view can be found in respected textbooks onECG (8).

In the seminal study of Haissaguerre et al. (1), theinvestigators defined early repolarization as “anelevation of the QRS-ST-segment junction (J-point) inat least 2 leads” (within the same territory; e.g., infe-rior or lateral leads) as being a sign of early repolari-zation. The amplitude of the J-point elevation had tobe at least 0.1 mV above the baseline level, as eitherQRS slurring or notching. The amplitude and slope ofthe ST-segment were not part of the definition.

In subsequent papers, Tikkanen et al. (3,4) fol-lowed this definition but also measured the degreeof so-called J-point elevation, which was stratifiedat levels of 0.1 and 0.2 mV. These investigatorsalso introduced the concept of the ST-segment slopehaving significance in the presence of early repolari-zation, showing that a horizontal or downward-sloping ST-segment is associated with greaterarrhythmic risk (4).

Thus, there has been considerable variation in thedefinition of early repolarization, as well as somecontroversy regarding the term itself. Spodick (9), forexample, regarded the term as a misnomer, whileothers believed that it was inappropriate andconfusing (10), a view which was challenged (11).

The aim of this paper is essentially to present aunified definition of early repolarization to assist futurestudies in the field by recommending measurementsthat should be made to facilitate sharing of data, withthe ultimate aim of having a greater understanding ofthe ECG pattern of early repolarization.

TERMINOLOGY

So that doubt can be avoided, an end-QRS notch is anotch that occurs on the final 50% of the downslopeof an R-wave occurring as the final segment of theQRS complex; that is, it links with the ST-segmentof the waveform (Figure 1A). It should be distin-guished from a notch midway on the downslope ofan R-wave (Figure 1B), because this may be due tofragmentation (12). Similarly, an end-QRS slur is anapparent slowing of the inscription of the waveformat the end of the QRS complex that merges with theST-segment of the complex (Figure 1A). Likewise, inthe context of this paper, a slur should occur in thefinal 50% of the R-wave downslope.

There is considerable variation in the use of theterm J point. For many cardiologists, this is taken as

the onset of the ST-segment (13), which mayequate with the termination of an end-QRSnotch, whereas others use the term for thepeak (1–3) or the onset (C. Antzelevitch, per-sonal communication, March 28, 2014) of anend-QRS notch. It is proposed that thefollowing terminology be used: 1) J onset (Jo)

Figure 2A clarifies these points for an end-QRSnotch. In the case of a slur (Figure 2B), Jo and Jp areelectrocardiographically the same point. However, forconsistency of measurement, it is proposed that theslur onset be regarded as Jp, rather than Jo, becausethis allows Jp to be used to denote both the peak notchand slur amplitude (Figure 2B). This means that inpublications, such as those of Haissaguerre et al. (1),Rosso et al. (2), and Tikkanen et al. (3,4), the term Jamplitude or J-point elevation equates with Jp ampli-tude, as confirmed by these investigators in contrib-uting to this consensus paper. Antzelevitch has usedJo to denote the J point when describing early repo-larization (personal communication, March 28, 2014).It also means that in publications such as the “ThirdUniversal Definition of Myocardial Infarction” (14),Jt equates with ST-segment amplitude in relation tothe definition of ST-segment elevation myocardialinfarction. The new terminology should clarify what isbeing measured in future studies and is recommendedfor use henceforth.

MEASUREMENT RECOMMENDATIONS

A major aim of this paper is to set out recommenda-tions with respect to measurements relating tothe early repolarization pattern. To this end, thefollowing definitions are presented.

NOTCHING AND SLURRING. To facilitate futurestudies, the following measurements should be made(Figure 2). All amplitude measurements are madewith reference to QRS onset.Notched QRS complex .1. The amplitude Jo at the onset of the notch2. The amplitude Jp at the peak of the notch3. The amplitude Jt at the end of the notch4. The duration D1 from Jo to Jp5. The duration D2 from Jo to Jt

Slurred QRS complex .1. The amplitude Jp at the onset of the slur2. The amplitude Jt at end of the slur3. The duration D2 from Jp to Jt

Jt =

FIGURE 1 QRS Notching and Slurring

(A) Electrocardiographic leads showing end-QRS notching in lead V4 progressing to end-QRS slurring in lead V6. End-QRS slurring is also

present in leads I and aVL. The arrows localize the notching or slurring. (B) Leads III and aVF show notching. In lead III, the notch peak is >50%

of the R-wave amplitude and could be regarded as fragmentation. In lead II, appearances on the R-wave downslope take the form of a slur, and

there is also a notch in lead aVF. They are most probably due to the same underlying physiological process. The arrows indicate the location of

the notches and slur.

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ST-SEGMENT SLOPE. The following measurementsshould be recorded when specifying slope (4).ST-segment s lope.1. ST-segment slope should be measured from Jt.2. The ST segment should be regarded as horizontal

or downward sloping if the amplitude of the ST-segment 100 ms after Jt (interval M) is less thanor equal to the amplitude at Jt (Figure 3). The ST-segment should be regarded as upward sloping ifthe amplitude of the ST-segment 100 ms after Jt(interval M) is greater than the amplitude at Jt.

3. If the researcher has not used Jt when measuringslope, any report must clearly state whether100-ms intervals such as K, L, and M (Figure 3) havebeen used.

NEW DEFINITION OF THE EARLY REPOLARIZATION

(END-QRS NOTCHING/SLURRING) PATTERN. A newdefinition of the early repolarization pattern on thebasis of current knowledge is urgently needed. It isentirely feasible that another definition will emergein the future, when further studies adopting themeasurement recommendations of this paper areavailable.

The majority of publications at the present time(e.g., refs. 1–4) adopt the amplitude of Jp in Figure 2 asthe reference point for measuring J-point elevation.The following criteria are therefore proposed untilfurther research clarifies the situation.

Early repolarization is present if all of the followingcriteria are met (Central Illustration):

FIGURE 2 End-QRS Notch and Slur Terminology

Jo

D2D2

D1

Jp Jt Jp Jt

A B

(A) Illustration of the amplitudes J onset (Jo), J peak (Jp), and J termination (Jt), as well as durations D1 and D2, in relation to an end-QRS notch,

as defined in the text. (B) Illustration of Jp and Jt, as well as D2, in relation to an end-QRS slur.

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1. There is an end-QRS notch or slur on the down-slope of a prominent R-wave. If there is a notch, itshould lie entirely above the baseline. The onset ofa slur must also be above the baseline.

2. Jp is $0.1 mV in 2 or more contiguous leads of the12-lead ECG, excluding leads V1 to V3.

3. QRS duration is <120 ms.

FIGURE 3 ST-Segment Slope Duration Measurements

A

Jo Jp JtM

L

K

(A) Illustration of duration measurements K, L, and M, each 100 ms, th

presence of a notch with reference amplitudes J onset (Jo), J peak (Jp)

measurements L and M, each 100 ms, used in the presence of an end-Q

If the ST-segment is upward sloping and fol-lowed by an upright T-wave, the pattern should bedescribed as “early repolarization with an ascendingST segment.”

If the ST-segment is horizontal or downward sloping,the pattern should be described as “early repolariza-tion with a horizontal or descending ST segment.”

B

M

L

Jp Jt

at could be used in the measurement of ST-segment slope in the

and J termination (Jt) also shown. (B) Illustration of duration

RS slur with onset Jp and termination Jt to measure slope.

CENTRAL ILLUSTRATION The Early Repolarization Pattern:A Summary of End-QRS Notching and Slurring With and WithoutST-Segment (J Termination) Elevation

Macfarlane, P.W. et al. J Am Coll Cardiol. 2015; 66(4):470–7.

The upper salmon line indicates the notch or slur amplitude, J peak (Jp), while the lower

purple line indicates the baseline used as a reference with respect to which amplitudes

should be measured. The blue lines indicate tangents to the initial component of the

R-wave downslope. All of these waveforms are illustrations of the early repolarization

pattern.

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The leads in which the notching or slurring occursshould be used as part of the description, so that, forexample, a complete report might state, “Early repo-larization with descending ST-segment in leads II, III,and aVF.”

If the ST-segment is ascending in at least 2 leads ineach territory and is horizontal or downward slopingin 1 lead, it should be defined as ascending and viceversa. If the ST-segment is horizontal in the inferiorleads and ascending in the lateral leads, the finalinterpretation will depend on the extent (more leads)and the (higher) amplitude of the end QRS slur ornotch, that is, on the territory where the early repo-larization is most prominent.

ST-SEGMENT ELEVATION WITHOUT NOTCHING OR

SLURRING. The consensus view of the group is thatST-segment elevation in the absence of a slur or notch(Figure 4) should not be reported as early repolariza-tion. This is in keeping with the early publicationson early repolarization (6,7), which included a notchor slur as part of the description of the pattern.

OVERALL QRS DURATION. It is recommended thatQRS duration be measured using those leads that donot exhibit a notch or slur. Whether the early repo-larization pattern reflects depolarization or repolari-zation is, in the consensus opinion, still notcompletely resolved, and speculation on this point isbeyond the scope of this paper. However, theconsensus view is that manual measurement of theQRS complex duration from the standard 12-lead ECGshould ideally be done from the leads without theearly repolarization pattern so that the overall QRSduration will not be overestimated. It is acknowl-edged that the automated measurement of QRSduration generally uses measurements from all leads,including those with notches, but this point is notelaborated here, other than to note that the normallimits of ECG measurements, as obtained from largepopulation samples, have essentially been derivedfrom the automated approach (15,16).

REGISTRY. It is recommended that a registry of pa-tients with early repolarization and evidence of idio-pathic ventricular fibrillation or sudden cardiac arrestbe established. This should be accompanied by acontrol group of subjects with ECGs that meet agreedcriteria for early repolarization but who have no his-tories of sudden cardiac arrest.

A registry is currently in the process of beingcompiled in the University Hospital of Bordeaux.Entry requires an ECG, a full history, and thecompletion of a form available on request. Contribu-tions to the inventory are invited.

AUTOMATED MEASUREMENTS. Cardiologists gener-ally obtain a visual impression of waveforms anddecide on the presence or absence of certain features.The aforementioned criteria provide guidelines forreporting early repolarization so as to quantitativelycharacterize visual waveforms. However, automated

FIGURE 4 Nonspecific ST-Segment Elevation

An illustration of an electrocardiogram showing moderate ST-segment elevation in leads I,

II, and aVF and more marked ST-segment elevation in leads V4 to V6, in the absence of any

end-QRS notching or slurring. It is recommended that this finding should not be described

as early repolarization. The arrows indicate the points of ST-segment elevation.

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methods for ECG analysis require additional preci-sion in the definition of a notch, for example. Thefollowing additional guidelines are offered for thispurpose.

ONSET OF END-QRS SLUR. With respect to detectingthe onset of an end-QRS slur, different methods canbe used. One approach (17) is to calculate a tangentfrom the peak of the R-wave through the followingdownslope and retain details of the slope. Calculationof the tangent can then progress through the QRScomplex after R peak. If the slope moves away fromthat of the initial tangent by more than a fixedamount, for example, 10� at a time scale equivalent to25 mm/s, then the slur onset should be accepted asthe point at which the slope clearly first deviates fromthe tangent by 10� (Figure 5).

Other techniques are available; for example, anend-QRS slur can be regarded as the reverse of a deltawave. Therefore, logic that detects a delta wave bylooking for slope changes in early QRS inscription caneffectively be mirrored to find slur onset at the end ofthe QRS complex (18).

Similarly, minimum amplitudes and durations ofthe notch must be used to detect a notch automati-cally. For example, Jp should exceed 0.05 mV (18) toensure that noise does not interfere with notchdetection.

SUMMARY RECOMMENDATIONS.

� It is recommended that researchers reporting end-QRS notching and slurring quote their criteria interms of Jo, Jp, and Jt. In Figure 2, Jt represents ST-segment onset from an ECG standpoint and shouldbe used when reporting ST-segment elevation.

� Whether a researcher uses all of these measure-ments or not, it is recommended that they be madeavailable for any cooperative study or internationalregistry.

� With respect to the definition of ST-segment slope,the recommendation is to use the time interval M.If this is not used, researchers must state whetherthey are using K or L (Figure 3). The onset of M, thatis, the location of Jt, is best determined fromanalysis of all 12 leads displayed in a time-alignedfashion, such that ST-segment onset can be deter-mined across all 12 leads. If any other method ofdetermining ST-segment slope were used, it wouldneed to be defined in detail.

DISCUSSION

In 2000, Gussak and Antzelevitch (19) presentedevidence in support of the hypothesis that the earlyrepolarization pattern denoted the presence of a

substrate that may pre-dispose to development oflife-threatening ventricular arrhythmias. Their defi-nition of the pattern included the presence of prom-inent J waves, or QRS notching or slurring, togetherwith ST-segment elevation. It was 8 years later whenidiopathic ventricular fibrillation was first linked with

FIGURE 5 End-QRS Slur Detection

10°

One possible method of determining the presence of an end-QRS

slur. If the angle between the initial downslope of the R-wave

and the end-QRS inscription exceeds 10�, a slur is defined as

present.

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large numbers of individuals having the early repo-larization pattern (1). In addition, there have beenmany papers (e.g., refs. 19,20) examining the experi-mental basis for notching and slurring. Not all in-vestigators are in complete agreement about theelectrophysiological basis of early repolarization, butthere is a consensus that the pattern of end-QRSnotching and slurring may, on occasion, be due tolate depolarization (9,21) rather than early repolari-zation (22). Some investigators take the view that themechanism responsible for end-QRS notching orslurring has not yet been established (23). Indeed,they suggest (23) that the term “early repolarization”should be replaced by “J waves.” There is not space inthis paper, which deals with measurement recom-mendations, to recount all of these discussions.

Leads V1 to V3 have been excluded from the newdefinition of early repolarization set out in this paperto avoid confusion with the Brugada pattern (24),which may occur in leads V1 to V3 and is regarded bysome as a form of early repolarization.

It is important that in future studies aimed at riskstratification and/or prevalence estimations of earlyrepolarization, investigators all use the same termi-nology and make the same measurements to describetheir findings. It is disconcerting that the prevalenceof early repolarization has been described as rangingfrom 2% to 31% (5). This could be ascribed to mis-understandings in what to measure, differences inECG recording equipment (e.g., filter settings), and,perhaps, racial variation (25).

None of this should preclude new measurementsfrom being introduced, but they should be presentedalongside the measurements recommended in thepreceding text.

VISUAL RECOGNITION OF THE EARLY REPOLARIZATION

PATTERN. Although this paper focuses principally

on the definitions of a notch and a slur and onterminology, cardiologists must interpret ECGsvisually, perhaps assisted by automated in-terpretations. Visual recognition of a slur can beproblematic. For example, if the display time scaleis increased from 25 to 50 mm/s, a slur might beconsidered present simply as a feature of thetime scale. It is therefore important to understandthat a slur should be reported only if there is adistinct change in the slope of the QRS complextoward Jt.

AUTOMATEDDETECTIONOFTHEEARLYREPOLARIZATION

PATTERN. Some of the problems in detecting slursdiscussed earlier apply equally well to automateddetection techniques. It is therefore importantthat the developers of software for the detection ofnotching and slurring adhere to the guidelinespresented. Even then, there are still likely to besubtle differences, particularly in the detection ofslur onset.

CLINICAL IMPLICATIONS. It is worth reiterating thatthe original definition of early repolarization referredto a combination of end-QRS notching or slurringtogether with ST-segment elevation and a tallT-wave. The more recent association between thenewer definition of early repolarization, as outlinedhere, and life-threatening cardiac arrhythmias wasindependent of increased Jt amplitude (1–3). Thework of Tikkanen et al. (4) and Rosso et al. (26) sug-gests that an upward-sloping ST-segment, followedby an upright T-wave in the presence of end-QRSnotching or slurring, is benign, whereas early repo-larization with a horizontal or downward-sloping ST-segment is potentially more serious. The ascendingST-segment has not predicted mortality or suddendeath in any of the general population samples.However, in the series of Rosso et al. (26), the ma-jority of emergency department cases with idiopathicventricular fibrillation were associated with horizon-tal or downward-sloping ST-segments, while theascending type was less common in the patients withearly repolarization syndrome resuscitated fromventricular fibrillation. Further research clearly needsto be undertaken using the measures described inthis paper.

Finally, in 1 study (27), notching or slurring plusJt elevation with Jt $0.1 mV occurred in 2.1% of1,496 apparently healthy, white adults (mean age37.4 � 12.6 years), whereas the prevalence was 29.3%if only notching or slurring was present without Jtelevation. This suggests that considerable cautionmust be exercised in interpreting the early repolari-zation pattern, as defined earlier.

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CONCLUSIONS

In view of the relatively high prevalence of theearly repolarization pattern without ST-segmentelevation in apparently healthy subjects (27) as perthe new definition, we believe it necessary to statethat, pending further research, in the absenceof syncope or a strong family history of juvenilesudden cardiac death, the finding of the earlyrepolarization pattern does not merit further in-vestigation, irrespective of ST-segment slope. Thispaper provides a basis on which future research canbe undertaken through shared data and standard-ized measurements.

ACKNOWLEDGMENTS The authors thank ElaineClark and Brian Devine, of the Electrocardiology Sec-tion, Institute of Cardiovascular and Medical Sciences,University of Glasgow, for assistance with preparationof the figures and Pamela Armstrong for attention todetail in the preparation of the final manuscript.

REPRINT REQUESTS AND CORRESPONDENCE: Prof.Peter W. Macfarlane, Institute of Cardiovascular andMedical Sciences, Electrocardiology Section, Uni-versity of Glasgow, Glasgow Royal Infirmary, NewLister Building, 10 Alexandra Parade, Glasgow G312ER, United Kingdom. E-mail: [email protected].

RE F E RENCE S

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KEY WORDS cardiac arrhythmias,electrocardiography, end-QRS notching/slurring, heart conduction system,sudden cardiac death, ventricular fibrillation