Slide 1: What’s wrong with this patient’s his-purkinje system?

Slide 2: There’s a left anterior fascicular block (LAFB). Formal criteria for LAFB. 1. Left axis deviation (-45 degrees and -90 degrees). Specifically, left axis deviation without LVH or inferior q-waves (suggestive of old MI) 2. qR pattern in lead aVL. 3. R-peak time in lead aVL of 45 ms or more. 4. QRS duration less than 120 ms.

Other common findings: rS in II, III, aVF. S in V5-V6.

Slide 3: Anatomy review! How does the left bundle conduct? The left bundle separates into 2 fascicles: anterior fascicle (LAF) and posterior fascicle (LPF).

What’s the underlying pathophysiology of LAFB? Fibrosis of the left anterior fascicle leads too slowed electrical conduction and LAFB. What causes fibrosis? Any condition with increased pressure in the LV can result in fibrosis, including: hypertension (most common), cardiomyopathy, infiltrative disease, and degenerative conduction disease.

Slide 4: How should I proceed after identifying a LAFB? Fortunately, no immediate work-u p or treatment is needed, but…

Ask why? If no known hypertension, consider home blood pressure monitoring and ordering an echocardiogram for structural heart disease.

Stay vigilant! LAFB suggests a maladaptive response to hypertension or structural heart disease, with corresponding increased risk of cardiac problems like atrial fibrillation or heart failure.

References

  • Surawicz B, Childers R, Deal BJ, Gettes LS, Bailey JJ, Gorgels A, Hancock EW, Josephson M, Kligfield P, Kors JA, Macfarlane P, Mason JW, Mirvis DM, Okin P, Pahlm O, Rautaharju PM, van Herpen G, Wagner GS, Wellens H; American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; American College of Cardiology Foundation; Heart Rhythm Society. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society. Endorsed by the International Society for Computerized Electrocardiology. J Am Coll Cardiol. 2009 Mar 17;53(11):976-81.PMID 19281930.
  • Demoulin JC, Kulbertus HE. Histopathological examination of concept of left hemiblock. Br Heart J. 1972 Aug;34(8):807-14. doi: 10.1136/hrt.34.8.807. PMID 5070112 .
  • Elizari MV, Acunzo RS, Ferreiro M. Hemiblocks revisited. Circulation. 2007 Mar 6;115(9):1154-63. PMID 17339573.
  • Nguyen KT, Vittinghoff E, Dewland TA, et al. Electrocardiographic Predictors of Incident Atrial Fibrillation. Am J Cardiol. 2016;118(5):714-719. PMID 29677051.
  • Mandyam MC, Soliman EZ, Heckbert SR, Vittinghoff E, Marcus GM. Long-term outcomes of left anterior fascicular block in the absence of overt cardiovascular disease. JAMA. 2013 Apr 17;309(15):1587-8. PMID 23592102.
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