Left Ventricular Mechanical Insights Into Left Bundle Branch Pacing and Left Ventricular Septal Pacing

BACKGROUND: The relationship between left ventricular (LV) mechanical efficiency and various modalities of left bundle branch area pacing (LBBAP) is not well understood. OBJECTIVES: The goal of this study was to evaluate the correlation between 2 different modalities of LBBAP, including left bundle branch pacing (LBBP) and LV septal pacing (LVSP) and myocardial work (MW), during spontaneous rhythm and LBBAP in patients with normal or moderately reduced LV ejection fraction. METHODS: Patients were retrieved from the TREEBEARD (Evaluation of Contemporary Cardiac Stimulation in Clinical Practice: Left, Biventricular, Right, and Conduction System Pacing; NCT06324682) prospective study and categorized into 2 groups based on whether they received LBBP or LVSP. MW was assessed using metrics such as global work index, global constructive work, global wasted work, and global work efficiency. RESULTS: Overall, 155 patients were included in the study (mean age 73.3 ± 14.3 years; 74.8% male), with 102 in the LBBP group and 53 in the LVSP group. In the LBBP group, all MW indices displayed a strong correlation between values recorded during spontaneous rhythm and LBBP. Conversely, the LVSP group exhibited moderate correlations for global work index (r = 0.535; P = 0.004), global constructive work (r = 0.587; P = 0.009), and global work efficiency (r = 0.503; P = 0.01). Global wasted work did not show a statistically significant correlation (r = 0.641; P = 0.13). CONCLUSIONS: In patients with preserved or moderately reduced LV ejection fraction, LBBP exhibited LV mechanical efficiency comparable to that of spontaneous LV activation. Conversely, LVSP is a valuable option, but LV mechanics is impaired, showing a reduced GWE of the left ventricle. (Evaluation of Contemporary Cardiac Stimulation in Clinical Practice: Left, Biventricular, Right, and Conduction System Pacing TREEBEARD; NCT06324682).