Electrocardiographic imaging of patients with heart failure with left bundle branch block and response to cardiac...

Area of Science:

• Cardiac Electrophysiology
• Medical Imaging
• Heart Failure Therapy

Background:

• Cardiac resynchronization therapy (CRT) effectiveness varies in patients with left bundle branch block (LBBB) and left ventricular (LV) dysfunction.
• Electrophysiologic substrate may influence conduction delays and pacing responses.
• Noninvasive epicardial mapping using electrocardiographic imaging (ECGI) can assess ventricular excitation.

Purpose of the Study:

• To investigate the role of electrophysiologic substrate in determining CRT response.
• To map ventricular activation patterns noninvasively using ECGI in patients with LBBB and LV dysfunction.

Main Methods:

• Electrocardiographic imaging (ECGI) was performed on 8 patients undergoing CRT.
• Ventricular activation patterns were analyzed during intrinsic conduction with LBBB and during CRT.

Main Results:

• Intrinsic conduction in LBBB showed heterogeneous LV activation with delayed or absent conduction, reflecting varied LV pathology.
• Latest LV activation sites varied, with the anterior LV showing susceptibility to block and slow conduction.
• CRT improved interventricular synchrony, but this did not correlate with QRS duration changes; pacing induced localized slow conduction in some patients.

Conclusions:

• LV activation is heterogeneous and unpredictable in LBBB with LV dysfunction, characterized by areas of slow or absent conduction.
• Functional conduction block lines can create barriers that interfere with paced wavefronts.
• Patient-specific electrophysiologic substrate properties are likely determinants of CRT outcomes.