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Effect of rate-dependent left bundle branch block on global and regional left ventricular function
Circulation
|May 1, 1983
Summary
Rate-dependent left bundle branch block (RDLBBB) impairs left ventricular ejection fraction and causes asynchronous contraction. This may mimic cardiac ischemia during exercise, highlighting the need for careful diagnosis.
Area of Science:
- Cardiology
- Physiology
Background:
- Rate-dependent left bundle branch block (RDLBBB) can affect cardiac function.
- Distinguishing RDLBBB from cardiac ischemia is clinically important.
Purpose of the Study:
- To investigate the impact of RDLBBB development on global and regional left ventricular function during exercise.
- To compare ventricular function in subjects with RDLBBB to a control group with normal conduction.
Main Methods:
- Upright bicycle exercise radionuclide angiography was performed on 7 subjects with RDLBBB and 13 controls.
- Left ventricular ejection fraction (LVEF) and wall motion were assessed at rest and during exercise (or immediately before/after RDLBBB onset).
Main Results:
- RDLBBB onset caused a significant decrease in LVEF in 6/7 patients (mean 6.0 ± 5.0%).
- LVEF did not increase from rest to maximal exercise in the RDLBBB group, unlike the control group.
- Asynchronous left ventricular contraction and hypokinesis were observed in RDLBBB patients, but not controls.
Conclusions:
- RDLBBB significantly alters global and regional left ventricular function.
- These functional changes associated with RDLBBB can be mistaken for left ventricular ischemia during exercise.