Background

QT interval measurement in the presence of right ventricular pacing (RVP) represents a clinical challenge due to altered ventricular activation resulting in a prolonged QT-interval. The aim of this study is to compare the QT interval in patients before and after ventricular pacing in order to develop a new formula for QT interval assessment in patients with RVP.

Methods and results:

All patients presenting to our pacemaker clinic with single- or dual chamber device were screened in this prospective observational study. Inclusion criteria were: no permanent right ventricular stimulation, an intrinsic QRS interval of <120 ms, and ventricular rate >35 bpm and <150 bpm. 12-lead electrocardiogram recordings during intrinsic rhythm and during right ventricular threshold testing (@ 80 and @100 bpm) were performed. The intrinsic QRS and QT time/JT time (QTi/JTi) were measured during intrinsic and subsequent RVP. All measurements were performed in 50 patients, according to our inclusion criteria,  (Mean age 74±11.3, male 33%) (RV-apical 30% and non-apical lead 70%). Based on our measurements, a new formula [QT (non-paced) = 70.8+ (0.78xQT (paced)] was derived. The predictive accuracy of this formula was then tested in 25 patients and a model’s performance of (r=0, 93) was confirmed.

Conclusion: 
We proposed a new simple formula to accurately estimate QT during RV stimulation. This formula can be easily utilized in clinical practice. Validation is ongoing with a large cohort of patients.