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Cases in Electrocardigraphy

The Diagnosis: Benign Early Repolarization

Brady, William J. MD; Harrigan, Richard MD; Chan, Theodore MD

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doi: 10.1097/01.EEM.0000292630.03504.06

    During his stay in the ED, this patient received sublingual nitroglycerin and intravenous lorazepam. Serial ECGs were performed, one every three to five minutes, which did not reveal change. With these medications, the patient's pain resolved after approximately 15 minutes.

    The initial (Figure 1) and subsequent ECGs were felt to demonstrate ST segment elevation due to benign early repolarization (BER). He was admitted to the ED chest pain center with a rule-out MI protocol. No further pain was noted.

    Figure 1
    Figure 1:
    Normal sinus rhythm with ST segment elevation in leads II, III, aVf, and V2 to V6. Also, the T waves are very prominent in leads V2 to V4. The initial, upsloping portion of the ST segment is concave, suggestive of a non-AMI etiology of the elevation.

    The serial enzymes and ECGs did not demonstrate an acute coronary event. The patient was discharged from the ED after performing an exercise stress test, which was negative.

    BER is felt to be a normal variant, not indicative of underlying cardiac disease.1,2 BER has been reported in men and women of all age groups in people of varying ethnic backgrounds, with men manifesting the pattern more often than women. The general population will have early repolarization on the ECG in approximately one percent of cases.3

    One to two percent of young military recruits demonstrate BER;4 it is also a common finding in athletes.5 In a large population-based study of BER, the mean age of patients with BER was 39 years with a range of 16 to 80. The syndrome was seen predominantly, however, in patients under age 50 and rarely encountered in those over age 70 (3.5%).3,6

    ST segment elevation is not a sensitive marker of acute myocardial infarction.7 In fact, numerous other non-infarction syndromes that occur in the chest pain patient will manifest electrocardiographic ST segment elevation. From the perspective of BER, it is encountered not infrequently in chest pain patients. For example, one prehospital study demonstrated that BER accounted for many of these ST segment abnormalities.8 Among adult ED chest pain patients with STE, BER was encountered almost as often as AMI.9

    The electrocardiographic definition of BER includes the following characteristics:

    • ST segment elevation.
    • Upward concavity of the initial portion of the ST segment (Figures 1–3).
    • Figure 2A
      Figure 2A:
      Representative examples of BER. A. ST segment elevation with J point elevation and concave morphology. Figure 2B. ST segment elevation with notching of the J point, a finding strongly suggestive of BER.
      Figure 3A
      Figure 3A:
      Representative examples of BER. A. Leads II and III revealing ST segment elevation. Figure 3B. Lead V2 with pronounced ST segment elevation and prominent T waves.
    • Notching or slurring of the terminal QRS complex (Figure 2B).
    • Symmetric, concordant T waves of large amplitude (Figures 1 and 3B).
    • Widespread or diffuse distribution of ST segment elevation on the ECG (Figure 1).
    • Relative temporal stability.2

    The STE begins at the “J” (or junction) point, the portion of the electrocardiographic cycle where the QRS complex ends and the ST segment begins. The degree of J point elevation is usually less than 3.5 mm.3 This STE morphologically appears as if the ST segment has been evenly lifted upward from the isoelectric baseline at the J point.10 This elevation results in a preservation of the normal concavity of the initial, up-sloping portion of the ST segment — T wave complex — a very important electrocardiographic feature used to distinguish BER-related ST segment elevation from STE associated with AMI.

    The STE elevation encountered in BER is usually less than 2 mm, but may approach 5 mm in certain individuals. Eighty percent of individuals demonstrate STE less than 2 mm in the precordial leads and less than 0.5 mm in the limb leads; only two percent of cases of BER manifest STE greater than 5 mm.3,11 The J point itself is frequently notched or irregular in contour, and is considered highly suggestive but not diagnostic of BER.3,10

    Prominent T waves of large amplitude and slightly asymmetric morphology also are encountered; the T waves may appear “peaked,” suggestive of the hyperacute T wave encountered in patients with AMI. The T waves are concordant with the QRS complex, and usually are found in the precordial leads. The height of the T waves in BER ranges from approximately 6.5 mm in the precordial distribution to 5 mm in the limb leads.3,6,10

    Figure 4A
    Figure 4A:
    A comparison of ST segment elevation types. A. Benign early repolarization. Figure 4B. Acute pericarditis, a difficult electrocardiographic distinction from BER. Note the similar concave ST segment elevation and the highly characteristic PR segment depression. Figure 4C. Acute myocardial infarction. Note the convex ST segment elevation.

    The degree of STE related to BER is usually greatest in the mid- to left precordial leads (leads V2 to V5). The ST segments of the remaining electrocardiographic leads are less often elevated to the extent observed in leads V2 through V5. The limb leads (I, II, III, aVl, and aVf) are less often observed to demonstrate STE. One large series reported that the limb leads revealed STE in only 45 percent of cases of BER. Lead aVr does not demonstrate STE due to BER.11 “Isolated” BER in the limb leads, i.e., no precordial STE, is a very rare finding.3,11 Such “isolated” STE in the inferior (II, III, and aVf) or lateral (I and aVl) leads should prompt consideration of another explanation for the observed ST segment abnormality.

    Most patients tend to demonstrate the BER pattern consistently over time in most cases. Certain individuals with BER, however, will demonstrate a changing magnitude of STE with transient fluctuations in the pattern. The magnitude of BER also may lessen over time as the patient ages.3,11


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