Effect of left bundle branch block on diastolic function in dilated cardiomyopathy

Area of Science:

• Cardiology
• Cardiac Electrophysiology
• Diastolic Function

Background:

• Dilated cardiomyopathy (DCM) is a common cause of heart failure.
• Left bundle branch block (LBBB) is frequently observed in DCM patients and can affect cardiac mechanics.
• Understanding the impact of LBBB on diastolic function is crucial for managing DCM.

Purpose of the Study:

• To evaluate the diastolic effects of left bundle branch block in patients with dilated cardiomyopathy.
• To investigate how LBBB influences mitral regurgitation and ventricular filling dynamics.

Main Methods:

• Retrospective analysis of echocardiograms (M-mode and Doppler), ECGs, and phonocardiograms.
• Comparison of 12 patients with LBBB and DCM to 40 patients with DCM but without LBBB.
• Assessment of electromechanical delay, pre-ejection contraction time, left ventricular relaxation time, and mitral regurgitation duration.

Main Results:

• Patients with LBBB showed shorter electromechanical delay but prolonged pre-ejection contraction and left ventricular relaxation times.
• The overall duration of mitral regurgitation was increased in the LBBB group, leading to significantly shorter ventricular filling times.
• Mitral regurgitation duration in LBBB patients was more sensitive to heart rate changes, with filling times often below 200 ms.

Conclusions:

• Left bundle branch block prolongs mitral regurgitation duration by increasing pre-ejection and relaxation times in DCM.
• This prolongation directly impairs diastolic function, significantly reducing the time available for left ventricular filling.
• The reduced filling time in LBBB patients with DCM may limit stroke volume and exacerbate heart failure symptoms.