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Left-axis deviation: etiologic factors in one-hundred patients
Insights
Left anterior fascicular block (LAHB) is uncommon in individuals under forty but increases with age, often linked to arteriosclerotic heart disease or degenerative processes. Myocardial infarction is a frequent, but not exclusive, cause.
Area of Science:
- Cardiology
- Electrophysiology
Background:
- Left anterior fascicular block (LAD) is a conduction abnormality.
- Its incidence and causes require further elucidation, particularly in relation to age and cardiac conditions.
Purpose of the Study:
- To analyze the clinical and electrocardiographic findings in patients with LAD.
- To identify the underlying mechanisms and causes of LAD in a consecutive case series.
Main Methods:
- Retrospective analysis of 100 consecutive cases diagnosed with LAD.
- Evaluation of clinical diagnoses, electrocardiographic patterns, and patient history.
- Correlation of LAD with conditions such as arteriosclerotic heart disease, myocardial infarction, and left ventricular hypertrophy.
Main Results:
- LAD incidence increases with age, being uncommon below forty.
- Left bundle branch block (LAHB) was the most frequent mechanism (40%), often associated with myocardial infarction or degenerative processes.
- Inferior myocardial infarction accounted for approximately one-sixth of LAD cases.
- Left ventricular hypertrophy was an uncommon cause of LAD.
Conclusions:
- LAHB is a significant mechanism contributing to LAD, with varied etiologies including infarction and primary conduction system disease.
- Age is a factor in LAD prevalence.
- Further investigation may be needed for unexplained LAD cases, potentially involving anterior wall hypertrophy.
Abstract:
Clinical and electrocardiographic findings were analyzed in 100 consecutive cases of LAD. Below the age of forty years, LAD was uncommon, but its incidence increased continuously thereafter. The most frequent primary clinical diagnosis was arteriosclerotic heart disease. The functional mechanism producing LAD most often was LAHB, responsible in about 40 per cent. Approximately half the instances of LAHB were associated with old myocardial infarction of septal, anterior, or lateral regions, but half were seen in the absence of infarction or clinical coronary sclerosis and are presumed due to primary degenerative processes within these specialized conducting fibers. Approximately one-sixth of the instances of LAD were due to loss of inferior forces following inferior myocardial infarction. Typical left ventricular hypertrophy was a distinctly uncommon cause of LAD. Last, in 24 patients with LAD the mechanism or cause was not evident initially, of which two were subsequently shown to represent a very mild degree of LAHB. Also it is suggested that asymmetric myocardial hypertrophy of the anterior wall may account for some instances of LAD not otherwise explained.
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