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Effects of left bundle branch block on left ventricular function in apparently normal subjects. Study by equilibrium
D De Nardo1, M Antolini, G Pitucco
1Dipartimento di Medicina Interna, II Università degli Studi di Roma, Italia.
Insights
Left bundle branch block (LBBB) significantly impairs left ventricular (LV) function, even in hearts without other issues. This study shows LBBB can reduce ejection fraction and cause abnormal heart wall motion.
Area of Science:
- Cardiology
- Cardiac Electrophysiology
- Nuclear Cardiology
Background:
- Left bundle branch block (LBBB) is a cardiac conduction abnormality.
- Its independent impact on left ventricular (LV) function in otherwise healthy hearts requires clarification.
Purpose of the Study:
- To assess the independent effects of chronic and intermittent LBBB on global and regional LV function.
- To evaluate LV performance in patients with LBBB but no other apparent cardiac disease.
Main Methods:
- Equilibrium radionuclide angiocardiography (RNA) performed at rest.
- Study included patients with chronic LBBB (Group I) and intermittent LBBB (Group II).
- Analysis of global LV ejection fraction and regional wall motion (septal, inferoapical, posterolateral).
Main Results:
- In chronic LBBB, 2/3 patients had LV ejection fraction <50% and all showed septal motion abnormalities.
- In intermittent LBBB, global LV ejection fraction decreased during LBBB episodes.
- Regional LV function (inferoapical, posterolateral) was reduced in LBBB patients, with persistent septal hypokinesis.
Conclusions:
- LBBB, whether chronic or intermittent, demonstrably deteriorates resting LV performance.
- These effects occur even in individuals with an otherwise normal heart structure and function.
- LBBB should be considered a significant factor affecting cardiac function independently.
Abstract:
To determine the independent effects of left bundle branch block (LBBB) on global and regional left ventricular (LV) function we performed equilibrium radionuclide angiocardiography at rest in 3 patients with chronic LBBB (group I, mean age 53.6 years and in 6 patients with intermittent LBBB (group II, mean age 41.5 years). All patients were judged to have an apparently normal heart. In 2 of 3 patients of group I a LV ejection fraction lower than 50% was observed, and in all 3 patients septal motion abnormalities were present. In all patients of group II the global LV ejection fraction was normal during normal conduction and decreased during LBBB; the inferoapical regional ejection fraction decreased in 5 of 6 cases and the posterolateral regional ejection fraction in 3 of 6 cases. Moreover, septal hypokinesis was observed both during normal and abnormal conduction in all group II patients. These findings seem to confirm that LBBB, chronic or intermittent, is able to deteriorate LV performance at rest, even in patients with an otherwise normal heart.