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E-1

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NARRATIVE INTERPRETATION E-1

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Image not available.

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Abnormalities
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Axis leftwards of −30 degrees. Broad QRS with rsR′ pattern and T-wave inversion leads V1–V3. Aberrantly conducted complex on rhythm strip.

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Synthesis
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Wide complex tachyarrhythmia, probably supraventricular in origin. (Possible atrial flutter with 2:1 AV conduction.) Aberrantly conducted complex on rhythm strip. RBBB with associated ST-T-wave changes. LAFB. Left-axis deviation.

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TEST ANSWERS:

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18, (19), 50, 64, 70, 72, 104.

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Comment: The differentiation of ventricular tachycardia versus supraventricular tachycardia with aberrancy is one of the most challenging aspects of clinical electrocardiography. Analyzing a number of factors can assist in the diagnosis; but in this tracing, conflicting criteria appear. The RBBB pattern present in lead V1 suggests aberrancy, but the specific rsR′ configuration is not classic. Conversely, the left axis favors ventricular ectopy. The rate of 158 somewhat favors ventricular tachycardia, but this finding is neither sensitive nor specific. The QRS duration of 0.13 s does not help to distinguish the origin of the tachyarrythmia.

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Remember that a patient may have an underlying conduction abnormality to explain the wide complex. This indeed turns out to be the case in this patient (see next tracing). If one makes a very careful search in lead aVF, tiny, notched P waves can be seen before and after the QRS, suggesting that the rhythm is atrial flutter with 2:1 AV conduction. Without serial tracings or more information, it would be difficult to conclude this diagnosis.

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FURTHER READING

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Akhtar  M, Shenasa  M, Jazayeri  M,  et al: Wide QRS complex tachycardia. Ann Intern Med 109:905–912, 1988.  [PubMed: 3190044]
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Tchou  P, Young  P, Mahmud  R,  et al: Useful clinical criteria for the diagnosis of ventricular tachycardia. Am J Med 84:53–56, 1988.  [PubMed: 3337132]
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Wellens  HJJ, Barr  FWHM, Lie  KI: The value of the electrocardiogram in the differential diagnosis of a tachycardia with a widened QRS complex. Am J Med 84:27–33, 1978.

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Clinical History
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A 77-year-old man with lightheadedness.

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Image not available.

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E-2

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NARRATIVE INTERPRETATION

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Image not available.

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Abnormalities
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Axis leftward of −30 degrees. Broad QRS with rsR′ pattern and T-wave inversion leads V1–V3.

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Synthesis
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Atrial fibrillation. Period of high-grade AV block with accelerated AV junctional rhythm. RBBB with associated ST-T-wave changes. Left anterior fascicular block. Left-axis deviation.

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TEST ANSWERS:

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20, 23, 46, 64, 70, 72, 104.

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Comment: When comparing this tracing with the previous electrocardiogram, one can now determine that the wide complex tachyarrhythmia was secondary to an underlying conduction abnormality and not to ventricular tachycardia. The present electrocardiogram ...

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