Left Ventricular "Longitudinal Rotation" and Conduction Abnormalities-A New Outlook on Dyssynchrony

Area of Science:

• Cardiology
• Echocardiography
• Cardiac Electrophysiology

Background:

• Complete left bundle branch block (CLBBB) leads to ventricular dyssynchrony, reducing systolic and diastolic efficiency.
• A unique clockwise rotation of the left ventricle (LV), termed "longitudinal rotation," has been observed in CLBBB patients.

Purpose of the Study:

• To quantify the longitudinal rotation of the LV in patients with CLBBB.
• To compare LV longitudinal rotation in CLBBB patients versus those with normal conduction or complete right bundle branch block (CRBBB).

Main Methods:

• Analysis of 60 patients with normal QRS, CRBBB, or CLBBB using stored DICOM 2D apical-4 chambers view cine clips.
• Utilized EchoPac software with the SAX-MV algorithm for 2D strain analysis, excluding the posterior segment.
• Recorded longitudinal rotation direction, peak angle, and time-to-peak rotation.

Main Results:

• All 21 CLBBB patients exhibited clockwise longitudinal rotation (mean peak angle: -3.9 ± 2.4°).
• This rotation was significantly larger than in normal QRS (-1.4 ± 3°, p=0.005) and CRBBB (0.1 ± 2.2°, p=0.00001) groups.
• Clockwise rotation correlated with QRS duration in non-RBBB patterns and was not linked to reduced ejection fraction or wall abnormalities.

Conclusions:

• Speckle-tracking echocardiography revealed significant clockwise longitudinal rotation in CLBBB patients.
• This finding differentiates CLBBB from normal conduction and CRBBB, highlighting a specific LV mechanical alteration.