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Electrical alternans in wide complex tachycardias.

M S Kremers, J M Miller, M E Josephson

    The American Journal of Cardiology
    |August 1, 1985
    PubMed
    Summary

    Electrical alternans, a QRS or T wave variation, frequently occurs in wide QRS complex tachycardias. This finding alone doesn't distinguish ventricular tachycardia from supraventricular tachycardia but can indicate accessory pathways in SVT.

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    Area of Science:

    • Cardiology
    • Electrophysiology
    • Medical Diagnostics

    Background:

    • Wide QRS complex tachycardias present diagnostic challenges, often requiring differentiation between ventricular tachycardia (VT) and supraventricular tachycardia (SVT).
    • Electrical alternans, characterized by amplitude variations in QRS or T waves, has been observed in various cardiac conditions.

    Purpose of the Study:

    • To investigate the frequency and diagnostic utility of electrical alternans in wide QRS complex tachycardias.
    • To determine if electrical alternans can help differentiate between VT and SVT.

    Main Methods:

    • Analysis of 156 electrocardiograms from 91 patients with wide QRS complex tachycardias (136 VT, 20 SVT).
    • Quantification of electrical alternans (≥0.1 mV amplitude variation) in QRS or T waves.
    • Comparison of alternans frequency, cycle length, QRS morphology, axis, and lead distribution between VT and SVT.

    Main Results:

    • Electrical alternans was present in 27% of tracings (38% of patients), with similar frequencies in VT (39%) and SVT (35%).
    • Tachycardias with alternans exhibited a shorter mean cycle length (p<0.05).
    • Alternans was more frequent in anterior leads (V2, V3) and observed in more leads during SVT than VT (p<0.005). All SVTs with alternans utilized atrioventricular bypass tracts.

    Conclusions:

    • Electrical alternans is common in wide QRS complex tachycardias but is not a standalone differentiator between VT and SVT.
    • The frequent presence of alternans in SVTs with wide QRS complexes, particularly those using bypass tracts, may aid in identifying their mechanism.

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