[Tall R waves in the right precordial leads as a possible expression of left septal fascicular block]
Paolo Alboni1, Anna Holzl1, Gian Franco Baggioni1
1Sezione di Cardiologia, Ospedale Accreditato Quisisana, Ferrara.
Insights
Diagnosing left bundle branch blocks affecting the septal fascicle is challenging. Current electrocardiogram (ECG) criteria suggest potential blocks, but definitive diagnosis remains elusive due to ECG variability and other heart conditions.
Area of Science:
- Cardiology
- Electrophysiology
- Human Anatomy
Context:
- The left bundle branch (LBB) is crucial for cardiac electrical conduction.
- Histological and physiological studies reveal LBB trifurcation into anterior, posterior, and septal fascicles.
- The septal fascicle is present in over 50% of human hearts, influencing ventricular depolarization.
Purpose:
- To review and evaluate proposed electrocardiographic (ECG) criteria for diagnosing left septal fascicular block (LSFB).
- To identify the limitations and challenges in the definitive diagnosis of LSFB.
- To differentiate LSFB from other cardiac conditions that may present with similar ECG findings.
Summary:
- Proposed ECG criteria for LSFB include tall R waves in V2/V1 (without right bundle branch block), absence of septal q waves, and normal QRS duration/axis.
- These criteria are suggestive but not definitive due to significant variability in normal ECGs.
- Confounding conditions like right ventricular hypertrophy or infarction can mimic LSFB, hindering accurate diagnosis.
Impact:
- Highlights the current diagnostic uncertainty of LSFB using non-invasive methods.
- Underscores the need for further research to refine ECG criteria or develop new diagnostic tools for LSFB.
- Improved diagnosis of LSFB could lead to better understanding of conduction abnormalities and patient management.
Abstract:
Histological, physiological and pathophysiological studies have shown that the left bundle branch mainly divides into three fascicles, and a septal (middle) fascicle is present in over half of human hearts. Electrocardiographic criteria for the diagnosis of the block of this fascicle have been suggested by some authors: tall R waves in lead V2 and sometimes in V1 in the absence of a right bundle branch block pattern or a well evident jump of R waves from V1 to V2, absence of initial septal q waves and/or possible small q waves in the right precordial leads, normal QRS duration and normal QRS axis. At present, this intraventricular block can only be suspected but not diagnosed with certainty even after clinical/instrumental exclusion of pathological situations associated with tall R waves in leads V1 and V2 (right ventricular hypertrophy, lateral infarction, severe septal hypertrophy) because of the marked variability of normal ECG and the potential presence of confounding diseases.
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