Left Posterior Fascicular Block - ECG

Left posterior fascicular block (LPFB) is also known as left posterior hemiblock (LPHB). In contrast to LAFB, LPFB is a rare finding. It is typical with negative QRS amplitude in lead I and positive QRS amplitudes in leads II and III. The ECG axis is deviated to the right (vertically).

 

Left Posterior Fascicular Block - ECGThis is a classic left posterior fascicular block – we see negative QRS amplitude in I (blue) and positive QRS in II and III (red). Leads aVL and aVF (red ellipse) suggest vertical deviation of ECG axis.
 

LPFB does not have a great significance when it is an incidental finding. Sometimes it may accompany myocardial infarction and it is emphasized that LPFB may be present in right ventricular overload.