Real-time three-dimensional systolic dyssynchrony index predicts pacing-induced left ventricular dysfunction and cardiomyopathy

BACKGROUND: Right ventricular pacing leads to left ventricular (LV) dyssynchrony, which is a critical factor in the pathophysiology of pacing-induced LV dysfunction (PIVD) and cardiomyopathy (PICM). OBJECTIVES: This study aimed to determine the incidence of PIVD and PICM and evaluate the prognostic value of the real-time three-dimensional echocardiography (RT3DE)-derived systolic dyssynchrony index (SDI), measured shortly after pacemaker implantation, in predicting their development. METHODS: In this prospective observational study, 108 patients undergoing permanent RV pacing. Only 60 patients with preserved baseline LV ejection fraction (LVEF ≥ 50%) were enrolled. Comprehensive echocardiography, including global longitudinal strain (GLS) and RT3DE for SDI (Tmsv 16-SD) calculation, was performed at baseline, 7-10 days, and 6 months post-implantation. Patients were classified at 6 months as preserved (LVEF reduction ≤ 10%, final LVEF ≥ 50%), PIVD (LVEF reduction > 10%, final LVEF ≥ 50%), or PICM (LVEF reduction > 10%, final LVEF < 50%). RESULTS: The patients' mean age was 62.4 ± 16.3 years, 32 patients were males (53.3%). Mean follow-up was 6.53 ± 0.75 months. Twenty-five patients (41.7%) developed LV impairment; of them, 16 (85%) patients had PIVD, and nine (15%) patients had PICM. While baseline characteristics were similar, the dysfunction group exhibited significantly higher SDI and worse GLS as early as 7-10 days post-pacing. At 6 months, there were significant differences between the preserved group (35 patients) and impaired LV group regarding LV EF (63.6 ± 5 vs. 49.8 ± 11.6, p < 0.001), GLS (- 15.6 ± 3 vs. - 10.9 ± 3.8, p < 0.001), SDI% (2.4 ± 1.2 vs. - 7.9 ± 5.9, p < 0.001), and excursion (5.8 ± 2.23 vs. 3.2 ± 2.1, p < 0.001). In multivariate analysis, both SDI (odds ratio [OR], 5.38; 95% CI, 1.56-18.52; p = 0.008) and GLS (OR, 1.39; 95% CI, 1.02-1.90; p = 0.040) at 7-10 days were independent predictors of 6-month dysfunction. Receiver operating characteristic analysis showed that an SDI > 1.49% predicted dysfunction with an area under the curve of 0.843 (84% sensitivity, 71% specificity). A clear gradient of worsening SDI and GLS was observed from Preserved to PIVD to PICM. CONCLUSIONS: Mechanical dyssynchrony quantified by RT3DE-derived SDI is a powerful, independent predictor of pacing-induced LV dysfunction, identifiable within the first week after implantation. This early measurement offers a critical opportunity for risk stratification and guided intervention to prevent the progression to overt cardiomyopathy.