Test Findings

Left Posterior Fascicular Block



  • Left posterior fascicular block occurs due to failure of conduction down the left posterior fascicle.
    • Look For

    • Right axis deviation 90° to 180° in the absence of other causes
    • Normal QRS duration <120ms
    • rS pattern in I and aVL: small R wave with large S wave
    • qR pattern in III and aVF
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