Paced QRS axis as a predictor of pacing-induced left ventricular dysfunction

Area of Science:

• Cardiology
• Electrophysiology
• Medical Devices

Background:

• Optimal right ventricular (RV) pacing site selection is crucial for patient outcomes.
• Current methods for determining pacing site effectiveness have limitations.

Purpose of the Study:

• To investigate the hypothesis that a normal paced QRS axis indicates physiological ventricular activation.
• To determine if a normal paced QRS axis leads to better long-term left ventricular (LV) function preservation.

Main Methods:

• Evaluated 187 patients requiring permanent RV pacing.
• Classified pacing sites as apical or non-apical via chest radiography.
• Defined a normal paced QRS axis as between -30° and 90° on electrocardiogram.
• Assessed LV systolic function by measuring ejection fraction changes post-implantation.

Main Results:

• A normal paced QRS axis (15% of patients) was associated with preserved LV ejection fraction (0±6% change).
• Abnormal paced QRS axis (85% of patients) correlated with decreased LV ejection fraction (-10±10% change).
• Normal paced QRS axis independently predicted preserved LV function, especially in non-apical pacing cases.

Conclusions:

• A normal paced QRS axis is a superior indicator of preserved LV function compared to radiographic assessment of pacing site.
• Electrocardiographic assessment of QRS axis provides valuable prognostic information for RV pacing.