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The left hemiblocks: significance, prognosis and treatment
Insights
Left hemiblocks, often signs of widespread left bundle branch disease, have varying prognoses. Pacing is considered for symptomatic patients with specific electrocardiographic changes or underlying heart conditions.
Area of Science:
- Cardiology
- Electrophysiology
- Histopathology
Background:
- The left bundle branch, a critical component of the cardiac conduction system, is not strictly bifascicular but rather fanlike or trifascicular.
- Left hemiblocks, specifically left anterior and posterior hemiblocks, are electrocardiographic manifestations of left bundle branch disease.
Purpose of the Study:
- To review the concept, significance, prognosis, and treatment of left hemiblocks.
- To elucidate the anatomical and histopathological basis of left hemiblocks.
- To clarify the prognostic implications of left hemiblocks, particularly in conjunction with right bundle branch block.
Main Methods:
- Review of existing literature on left hemiblocks.
- Analysis of electrocardiographic features of left anterior and posterior hemiblocks.
- Examination of histopathological findings in cases of left bundle branch disease.
Main Results:
- Left hemiblocks are indicative of more widespread left bundle branch disease, often degenerative.
- The association of left hemiblock with right bundle branch block signifies a poor prognosis, especially in acute myocardial infarction.
- Prognosis in chronic cases depends heavily on the underlying pathology.
Conclusions:
- Patients with partial bilateral bundle branch block warrant investigation and potential pacing if symptomatic, showing PR interval lengthening, cardiomyopathy, or large anterior infarction.
- Asymptomatic individuals with primary conduction system disease are not typically candidates for prophylactic pacing.
Abstract:
This review article is concerned with the concept of left hemiblocks and analyses their significance, prognosis and treatment. It first stresses that the left bundle branch is not sensu stricto a bifascicular structure since it generally is either fanlike, or trifascicular. The anatomical situation, however, remains compatible with the physiological concept of the hemiblocks. The electrocardiographic features of left anterior and posterior hemiblocks are described. A histopathological investigation clearly demonstrates that both are signs of left bundle branch disease, often degenerative in nature and more widely spread than expected from the electrocardiographic terminology. The association of a left hemiblock with right bundle branch block is frequently considered as sign of poor prognosis. This is true in the setting of acute myocardial infarction where it accompanies large infarcts. In chronic cases, the prognosis is primarily influenced by the underlying pathology. Patients with partial bilateral bundle branch block should be investigated and, if needed, paced when they have symptoms, a PR interval which lengthens with the course of time, or signs of cardiomyopathy, or large anterior infarction. Asymptomatic individuals with apparent primary disease of the conducting system are neither studied, nor considered for prophylactic pacing.