Functional abnormalities in isolated left bundle branch block. The effect of interventricular asynchrony.

Area of Science:

• Cardiology
• Cardiac Electrophysiology
• Cardiovascular Imaging

Background:

• Left bundle branch block (LBBB) is a cardiac conduction abnormality affecting ventricular activation sequence.
• Understanding the functional consequences of LBBB on ventricular mechanics and hemodynamics is crucial for patient management.

Purpose of the Study:

• To investigate the impact of isolated left bundle branch block (LBBB) on left and right ventricular function and timing.
• To compare cardiac mechanical events in LBBB patients with normal subjects.

Main Methods:

• Utilized a multimodal approach including apexcardiography, phonocardiography, electrocardiography, echocardiography (2D and dual M-mode), and radionuclide ventriculography (RNV).
• Compared 18 patients with isolated LBBB to 10 normal control subjects.

Main Results:

• LBBB demonstrated significant delays in left ventricular systolic and diastolic events, shortening diastole and increasing the right to left ventricular diastolic time ratio.
• Decreased first heart sound (S1) amplitude (S1/S2 ratio) was observed in LBBB, attributed to widened separation of valvular contributors.
• Abnormal interventricular septal motion in LBBB reflected asynchronous ventricular contraction and ejection.
• RNV showed reduced septal regional ejection fraction and a lower global ejection fraction in LBBB patients compared to controls.

Conclusions:

• Isolated LBBB disrupts normal interventricular synchrony, leading to impaired left ventricular function.
• The study highlights significant alterations in diastolic timing, heart sound characteristics, and regional/global ejection fraction in LBBB.
• These findings underscore the mechanical consequences of LBBB on overall cardiac performance.