Impact of Right Ventricular Pacing Burden on Left Ventricular Deformation and Rotational Mechanics: A Cohort Study

Background Permanent right ventricular pacing may impair left ventricular function through abnormal electrical activation and mechanical dyssynchrony. Early effects on myocardial mechanics in structurally normal hearts remain unclear, as ejection fraction may not detect subtle dysfunction. Speckle-tracking echocardiography allows sensitive assessment of myocardial deformation. This study evaluated the short-term impact of right ventricular pacing burden on left ventricular function and mechanics Methods This prospective study included 117 patients undergoing permanent pacemaker implantation for conduction abnormalities (single-chamber or dual-chamber). A pacing burden threshold of 40% was selected a priori, based on prior evidence of this level as a clinically meaningful inflection point for pacing-induced left ventricular dysfunction. Patients were stratified into ≤ 40% (n = 50) and > 40% (n = 67) pacing-burden groups. Clinical and echocardiographic evaluation, including conventional and speckle-tracking imaging, was performed at baseline and 6 months. Results Among 117 patients (mean age 61.8 ± 13.3 years; 51.3% female) stratified by pacing burden into ≤ 40% (n = 50) and > 40% (n = 67) groups, global longitudinal strain (GLS) declined significantly in the > 40% group (18.7 ± 4.8% vs 16.3 ± 3.7%, p < 0.001; group× time interaction p = 0.05) but was unchanged in the ≤ 40% group. LVEF and circumferential strain declined numerically more in the > 40% group, without a significant group× time interaction. Radial strain and rotational mechanics (twist, torsion) did not change significantly in either group. Pacing burden > 40% (OR 2.32, 95% CI 1.01–5.37) and RV apical pacing site (OR 2.62, 95% CI 1.07–6.39) were independently associated with reduced GLS at 6 months (both p < 0.05). Conclusion Increased right ventricular pacing burden is associated with early impairment of left ventricular GLS, with a less certain effect on circumferential strain and no significant effect detected on radial or rotational mechanics at 6 months. Speckle-tracking echocardiography, particularly GLS, may enable earlier detection of subclinical dysfunction than ejection fraction.