Left posterior fascicular block (LPFB) or Left posterior hemiblock (LPH) is a type of unifascicular block of left bundle branch with typical ECG pattern – right axis deviation
Isolated LPFB is rare and most often the cause of right-axis deviation is right ventricular hypertrophy (RVH)
For diagnosis of LPGB ECG and clinical characteristics of RVH and asthenic habitus must be absent
ECG features
Right axis deviation ≥+90 degrees
RS or rS pattern in I and aVL
qR pattern in II, III, aVF
QRS duration < 120 ms
Right axis deviation
QRS is POSITIVE (dominant R wave) in Lead II, Lead III and aVF
QRS is NEGATIVE (dominant S wave) in Lead I
Picture 1 Right axis deviation
ECG 1 Left posterior fascicular block (LPFB, LPH)
right axis deviation + 106°
RS pattern in lead I, rS pattern in lead aVL
qR pattern in II, III, aVF
slightly prolonged QRS duration – 110ms
sinus rhythm at a rate 75 bpm
Causes
Left bundle branch consists of two fascicles – Left anterior fascicle and Left posterior fascicle
Normal activation of the left-ventricular free wall spreads simultaneously from two sites. When a block in either the LAF or LPF is present, activation of the free wall proceeds from one site instead of two. This changes the waveforms of the QRS complex and produces a shift of the QRS complex axis
Isolated fascicular block is often benign
The incidence of fascicular block in otherwise normal individuals is 2% to 5% and increases with age
References
Brian Olshansky, Mina K. Chung, Steven M. Pogwizd, Nora Goldschlager, Chapter 2 - Bradyarrhythmias—Conduction System Abnormalities, Editor(s): Brian Olshansky, Mina K. Chung, Steven M. Pogwizd, Nora Goldschlager, Arrhythmia Essentials (Second Edition), Elsevier, 2017, Pages 28-86, ISBN 9780323399685, https://doi.org/10.1016/B978-0-323-39968-5.00002-0.
CAMM, A. J., LÜSCHER, T. F., & SERRUYS, P. W. (2009). The ESC textbook of cardiovascular medicine. Oxford, Oxford University Press
STRAUSS, David G., et al. Marriott's Practical Electrocardiography. Wolters Kluwer, 2021
