Distinctive Left Ventricular Activations Associated With ECG Pattern in Heart Failure Patients

Area of Science:

• Cardiology
• Electrophysiology
• Heart Failure Research

Background:

• Patients with heart failure and narrow QRS or nonspecific intraventricular conduction delay (NICD) respond less effectively to cardiac resynchronization therapy (CRT) than those with left bundle branch block (LBBB).
• Understanding the differences in left ventricular (LV) activation patterns is crucial for optimizing CRT in heart failure patients.

Purpose of the Study:

• To compare LV activation patterns in heart failure patients with narrow QRS and NICD to those with LBBB.
• To elucidate the electrophysiological mechanisms underlying CRT response differences.

Main Methods:

• High-density 3-dimensional electroanatomic mapping of the LV in 52 heart failure patients (18 narrow QRS, 11 LBBB, 23 NICD).
• Analysis of LV activation patterns, including LV breakthrough sites, propagation, and areas of latest activation.
• Correlation of activation maps with scar imaging in 71% of patients.

Main Results:

• LBBB patients exhibited a single LV breakthrough, prolonged transseptal activation, homogeneous LV propagation, and latest activation at the basal lateral LV.
• Narrow QRS and NICD patients showed multiple LV breakthroughs (5±2 and 4±2, respectively, vs. 1±1 in LBBB), early/pre-QRS LV electrograms with Purkinje potentials.
• Rapid LV propagation was observed in narrow QRS patients, while NICD patients displayed more heterogeneous propagation with limited late activation areas associated with LV scar.

Conclusions:

• Left ventricular activation mechanisms differ significantly between LBBB patients and those with narrow QRS or NICD.
• These distinct activation patterns, characterized by multiple breakthroughs and heterogeneous propagation in narrow QRS/NICD groups, likely contribute to their poorer response to cardiac resynchronization therapy.