Middle-aged Man With Chest Pain After Exercise

A42-year-old man with a history of hypertension presents to an outpatient clinic with chest pain that began the day before, after he had worked out at his health club. The discomfort increases when he walks and worsens somewhat with inspiration. No associated symptoms are noted. Results of a physical examination are normal; no chest wall tenderness is evident. Because certain features of the presentation suggest an acute coronary syndrome, a 12-lead ECG is obtained, which is shown here. The patient is referred to the emergency department (ED) for further evaluation. Before he arrives at the ED, his pain spontaneously resolves. In the ED, physical examination results and ECG findings are unchanged from those of a few hours earlier. Results of a “rule out myocardial infarction (MI)” evaluation in the ED chest pain center are unremarkable. The patient is discharged with a diagnosis of chest pain of unclear etiology. The results of an exercise stress test performed the next day are also negative. What best explains the findings on this man’s ECG? A. Acute pericarditis. B. Benign early repolarization. C. Left ventricular hypertrophy (LVH). D. Right bundle branch block (RBBB). E. Acute MI.DISCUSSION
The ST-segment elevation seen in this patient’s ECG (Figure 1) can be attributed to benign early repolarization (BER). This common cause of ST-segment elevation is a normal variant and does not indicate an underlying coronary or cardiac process. ECG features of BER. BER is defined electrocardiographically by widespread ST-segment elevation that occurs at the J (or junction) point and that shows characteristic concavity in the initial portion of the ST segment (Figure 2). Other features of BER include:

• Notching or slurring of the terminal portion of the QRS complex at the J point (Figure 3).
• Symmetric, concordant, large T waves (see Figures 3 and 4).
• Relative temporal stability.¹

The ST-segment elevation begins at the J point with preservation of the normal concavity of the initial, upward- sloping portion of the ST segment– T wave complex. Morphologically, it appears as if the ST segment has been evenly raised off the baseline starting at the J point (see Figure 2).¹ This feature of the elevated ST segment is very important; it is used to distinguish ST-segment elevation associated with BER from the ST-segment changes seen in acute MI. The magnitude of the ST-segment elevation seen in BER is usually minimal; heights of less than 2 mm are common. Rarely, the ST segment may be markedly elevated, approaching 5 mm.^2,3 The degree of ST-segment elevation is usually greatest in the mid to left precordial leads (V₂ through V₅). The ST segments in the remaining leads are less likely to be elevated to the extent seen in leads V₂ through V₅. ST-segment elevation occurs less often in the limb leads (I, II, III, aVL, and aVF); one large series showed ST-segment elevation in these leads in only 45% of patients with BER and ST-segment elevation in the precordial leads. “Isolated” BER in the limb leads (ie, characteristic ST-segment elevation in the limb leads that is not accompanied by precordial ST-segment elevation) is a very rare finding.^2,3 Such isolated ST-segment elevation in the inferior (II, III, and aVF) or lateral (I and aVL) leads should prompt consideration of another explanation for the ST-segment abnormality-for example, acute MI. The J point itself is frequently notched or irregular in contour in BER (see Figure 3).^1,2 Prominent T waves of large amplitude and slightly asymmetric morphology are also seen (see Figure 4). Such T waves are concordant with the QRS complex and are usually found in the precordial leads.^1,2,4,5 Most patients with BER exhibit the characteristic ECG pattern consistently over time; however, as a person ages, the magnitude of the ST-segment elevation often lessens. Epidemiology of BER. BER occurs with a frequency of approximately 1% in the general adult population.² Among military recruits, the frequency of BER is between 1% and 2%6; BER is also commonly seen in competitive athletes.⁷ Although BER is found in adults of all ages, it is seen primarily in persons younger than 50 years and is rare in persons older than 70 years; the mean age of patients with BER is about 40 years (range, 15 to 80 years).² BER is seen in men significantly more often than in women.² For unknown reasons, BER is more frequently noted in black men between the ages of 20 and 40 years than in the general population.⁴ Early repolarization is also encountered in 20% to 25% of ED patients with chest pain-again, for unknown reasons.^8,9Distinguishing between BER and other causes of ST-segment elevation. A variety of benign and malignant ECG syndromes feature ST-segment elevation (Table). In addition to BER, more common ones include:

• Acute pericarditis.
• LVH.
• Left or right BBB.
• Acute MI.

Making a correct diagnosis based on the ECG is often challenging. The absence of prominent electrical forces in the precordial leads rules out LVH, and a widened QRS complex rules out BBB. BER versus acute pericarditis. It is more difficult to distinguish between BER and acute pericarditis based on the ECG. The ST-segment changes seen in these 2 syndromes are similar; both feature diffuse, concave ST-segment elevation. However, the PR segment is entirely normal in BER, whereas in acute pericarditis, the PR segment is often depressed, particularly in the inferior leads and in lead V₆. The PR segment may also be elevated in lead aVR in this setting. The ratio of the ST-segment elevation to the height of the T wave can also be used to distinguish between acute pericarditis and BER. An ST segment–T wave ratio greater than 0.25 strongly supports an electrocardiographic diagnosis of acute pericarditis. BER versus acute MI. Several ECG features are used to distinguish between BER and acute MI (Figure 5).

• Waveform of the ST segment–T wave complex. In acute MI, this portion of the segment is either obliquely straight or convex, while in BER, the segment is concave.
• Presence of reciprocal ST-segment change. A finding of ST-segment depression distant from the ST-segment elevation strongly suggests that the cause of the ST-segment elevation is acute MI.¹⁰
• Evolutionary changes. The ECG features of BER are static and unlikely to change over short periods of time, while in acute MI, the ECG is dynamic and demonstrates rapid change over short intervals.

Even with these guidelines, it can still be difficult at times to distinguish between BER and acute MI. Sharkey and colleagues¹¹ noted that in approximately one third of patients who inappropriately received thrombolytic therapy for presumed acute MI, BER was actually responsible for the ST-segment elevation seen on their ECGs. Outcome of this case. At primary care follow-up, the patient continues to do well and reports no recurrence of the problem.

References:

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