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    6.6
    Home > ECG findings

    6.6

    Minnesota Code 6-6: intermittent aberrant AV conduction — wide supraventricular beats and how they are told apart from ventricular beats.

    Code 6.6 — Minnesota Code 6-6: intermittent aberrant AV conduction. Some supraventricular beats, which originate above the ventricles, are conducted to the ventricles with an abnormal, widened QRS shape, while other beats in the same recording are conducted normally. This is aberrant conduction: the impulse meets a bundle branch that has not yet recovered (is refractory), most often the right bundle branch, so it spreads through the ventricles by an unusual route.

    Minnesota Code 6Aberrant conductionIntermittent finding
    Origin of beatssupraventricular
    QRSintermittently widened
    Typical shapeRBBB-like
    Key differentialventricular beats
    Normally conducted supraventricular beat with narrow QRS compared with an aberrantly conducted beat with wide QRS of right bundle branch block shape Normal conduction narrow QRS QRS 90 ms Aberrant beat P present, wide QRS QRS 130 ms
    Figure 1. Left: normally conducted beat (narrow QRS). Right: aberrantly conducted beat of supraventricular origin — preceded by a P wave, but with a wide, RBBB-like QRS.

    When it occurs

    • Premature atrial beats arriving early, before the bundle branches have recovered
    • The Ashman phenomenon in atrial fibrillation: a short RR interval after a long one
    • Rate-dependent bundle branch block that appears only above a certain heart rate
    • Supraventricular tachycardia with functional bundle branch block

    Clinical significance

    Aberrant conduction itself is usually a functional, harmless phenomenon. Its main importance is diagnostic: wide QRS beats or wide-complex tachycardia can be supraventricular with aberrancy, or ventricular in origin, and the latter is potentially more dangerous. A preceding P wave, a typical bundle branch block shape and the clinical context help the doctor distinguish them. When in doubt, a wide-complex tachycardia is treated as ventricular tachycardia until proven otherwise. Rate-dependent bundle branch block may be an early sign of conduction-system disease.

    Seek emergency care

    if you have a fast heartbeat with dizziness, fainting, chest pain or breathlessness.

    References

    1. Prineas RJ, Crow RS, Zhang ZM. The Minnesota Code Manual of Electrocardiographic Findings. 2nd ed. London: Springer; 2010. doi:10.1007/978-1-84882-778-3
    2. Surawicz B, Childers R, Deal BJ, Gettes LS. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances. Circulation. 2009;119(10):e235–e240. doi:10.1161/CIRCULATIONAHA.108.191095
    3. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia. Circulation. 2016;133(14):e506–e574. doi:10.1161/CIR.0000000000000311

    This article is for general information and does not replace a consultation with a doctor. ECG findings must be interpreted by a physician together with symptoms and other tests.

    Published on 14 May 2019