Why the study?
Does incomplete LBBB alter the normal direction of septal depolarization or cause electromechanical delay in the left ventricle?
Does incomplete LBBB alter the normal direction of septal depolarization or cause electromechanical delay in the left ventricle?
The findings suggest that 'incomplete LBBB' does not alter normal septal depolarization or cause electromechanical delay, prompting the suggestion to use the term 'initial force abnormality' instead.
Incomplete LBBB may not signify conduction delay; challenges consensus on mechanism and leaves reclassification as initial force abnormality open for validation.
The direction of the initial 20 to 30 msec forces of multiple unipolar and transseptal bipolar intraventricular electrocardiograms was examined in five patients with and five without incomplete left bundle-branch block (LBBB) and in one patient with complete LBBB. The data obtained were consistent with preservation of the normal left-to-right and apex-to-base direction of septal depolarization in patients with apparent, incomplete LBBB. Furthermore, no evidence of electromechanical delay in the left ventricle could be ascribed to this conduction defect. Until the minute details of normal and abnormal human septal excitation become known, it is suggested that the more descriptive and less mechanistic term "initial force abnormality" be substituted for "incomplete LBBB."
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Leighton et al. (1967) studied this question.
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