Related Experiment Videos
Endocardial activation of left bundle branch block
Insights
Right ventricular activation precedes left ventricular activation in patients with left bundle branch block (LBBB). Left ventricular activation in LBBB is heterogeneous, with coronary artery disease patients showing longer activation times.
Area of Science:
- Cardiology
- Electrophysiology
Background:
- Left bundle branch block (LBBB) affects cardiac electrical conduction.
- Understanding LBBB activation patterns is crucial for patient management.
Purpose of the Study:
- To investigate the endocardial activation sequence in patients with LBBB.
- To compare activation times across different patient groups.
Main Methods:
- Endocardial catheter mapping in 18 patients with LBBB.
- Patients categorized into three groups: no organic heart disease, cardiomyopathy, and coronary artery disease with infarction.
- Analysis of left and right ventricular endocardial activation sites and times.
Main Results:
- Right ventricular activation consistently preceded left ventricular activation.
- Left ventricular endocardial activation occurred via right-to-left transseptal pathways.
- Total left ventricular endocardial activation time was significantly longer in patients with coronary artery disease and LBBB compared to other groups.
Conclusions:
- Right-to-left transseptal activation is the likely mechanism for left ventricular activation in LBBB.
- Left ventricular activation patterns in LBBB are heterogeneous.
- Coronary artery disease exacerbates delays in left ventricular activation in LBBB patients.
Abstract:
Endocardial catheter mapping was performed in 18 patients with left bundle branch block (LBBB). Four patients had no organic heart disease (group I), six had cardiomyopathy (group II), and eight had coronary artery disease and previous infarction (group III). Twelve patients had one septal site of left ventricular endocardial breakthrough, while six had two left ventricular endocardial breakthrough sites, with one site always being septal. There was no significant difference among the groups with respect to time of left ventricular breakthrough (group I, 44 msec after the onset of the QRS complex; group II, 58 msec; and group III, 51 msec). Total left ventricular endocardial activation time was significantly longer in group III (119 msec) than group I (81 msec; p less than .05) and group II (61 msec; p less than .001). Duration of total right ventricular endocardial activation was 36 msec (seven patients). The final site of right ventricular activation was at 44 msec after the onset of the QRS complex. We conclude that (1) right ventricular activation occurs before initiation of left ventricular activation in patients with LBBB, (2) left ventricular endocardial activation in patients with LBBB most likely occurs as a result of right-to-left transseptal activation, (3) left ventricular endocardial activation sequence in patients with LBBB is heterogeneous, and (4) patients with coronary artery disease and LBBB have significantly longer total left ventricular endocardial activation times than patients with no organic heart disease or those with cardiomyopathies.