QT Interval Evaluation in Right Ventricular Pacing: Validation of a Novel Formula

BACKGROUND: QT interval measurement in the presence of right ventricular pacing (RVP) represents a clinical challenge. We therefore aimed to derive and validate a formula for QT estimation during RVP in a large cohort of pacemaker patients. METHODS AND RESULTS: We prospectively enrolled 100 patients in a derivation cohort and 487 in a validation cohort. Eligible patients had implanted pacemakers or implantable cardioverter-defibrillators, preserved atrioventricular conduction, and a narrow native QRS. Standardized 12-lead ECGs were recorded during intrinsic rhythm, atrial pacing (AP), and RVP at matched heart rates. Linear regression of QT during non-paced rhythm against paced QT yielded the equation: QT_non-paced = 139.23 + 0.55 × QT_paced. In the validation cohort (mean age 71 ± 13 years, 72% male), application of the formula showed a significant correlation between predicted and observed QT values (r = 0.50, p < 0.001). Bland-Altman analysis demonstrated a modest mean overestimation of 15 ms, with consistent accuracy across subgroups defined by sex, device type, and lead position. Compared directly with the Bogossian method, our formula showed superior performance, with a lower mean absolute deviation (26.2 vs. 39.9). CONCLUSION: This novel, heart rate-independent formula provides a reliable method for estimating the intrinsic QT interval from paced measurements. It represents a practical tool to improve QT assessment and arrhythmic risk evaluation in patients with RVP, with potential implications for clinical decision-making and drug safety monitoring.