Progressive Paced QRS Widening: An Electrocardiographic Marker for Predicting Cardiac Resynchronization Therapy Upgrade.

Background: Chronic right ventricular (RV) pacing may lead to left ventricular dysfunction requiring cardiac resynchronization therapy (CRT) upgrade. This study aimed to determine whether paced QRS duration (pQRSd) and its progression over time predict the need for CRT upgrade.

Methods: In this retrospective study of 410 RV pacing-dependent patients who underwent device surgery at two centers between 2017 and 2022, we analyzed pQRSd immediately after pacemaker implantation and before potential CRT upgrade. ΔpQRSd was defined as the difference between these measurements.

Results: Among 410 patients, 51 (12.4%) underwent CRT upgrade. Multiple regression analysis revealed that CRT upgrade was significantly associated with age (p = 0.004), pQRSd before upgrade (p < 0.0001), and baseline left ventricular ejection fraction (LVEF) (p < 0.0001). ΔpQRSd was significantly larger in CRT upgrade patients (16 ms vs. 0.6 ms, p < 0.0001). ROC analysis established optimal cut-off values: pQRSd > 154 ms post-pacemaker insertion (sensitivity 80%, specificity 45%, AUC = 0.62), pQRSd > 166 ms before CRT upgrade (sensitivity 88%, specificity 73%, AUC = 0.83), and ΔpQRSd > 6 ms (sensitivity 73%, specificity 69%, AUC = 0.72).

Conclusion: Progressive widening of pQRSd represents a novel, clinically accessible marker for identifying patients at high risk for CRT upgrade. Monitoring pQRSd trends through routine electrocardiogram (ECG) provides an effective strategy for early identification of patients who might benefit from CRT before developing advanced heart failure.