A proposal for a novel formula for measurement of corrected QT interval in patients undergoing left bundle branch...

Prolongation of the QT interval is associated with malignant ventricular arrhythmias. However, measuring the QT interval is difficult in some clinical conditions, like ventricular paced rhythm. In this study, we aimed to propose a novel formula that measures the QT interval in patients who underwent pacemaker implantation via left bundle branch area pacing (LBBaP).

This is a single-center, retrospective preliminary study (n = 63). All patients underwent pacemaker implantation via LBBaP. Electrocardiographic (ECG) parameters [QRS duration (QRSd), QTc interval (Bazett, Fridericia, Framingham, Hodges, Rautuharju, Spline), Ventricular rate, JT interval] were measured and analyzed before and after the LBBaP.

The mean age of the study population was 68 ± 13 years, and 39 (62 %) patients were female. The patients' mean left ventricular ejection fraction (LVEF) was 57.9 ± 4.78 %. The mean QT duration of the patients was 437.73 ± 55 msec at baseline and 427.17 ± 38.79 msec after the procedure. The Hodges formulation before and after LBBaP yielded the closest QTc measurements. As a result of our analysis, we produced the formula for patients who underwent LBBaP and were in paced rhythm: QTc (Dogan) = QTc(H)X0.97 = [QT + 1.75 (HR - 60)]x0.97.

There is no precise formula for measuring QTc in patients with ventricular-paced rhythm and pacemaker dependency. In patients with conventional pacemaker implantation, the underlying QT has long been calculated by subtracting 50 msec from the QT duration in a ventricular-paced rhythm. LBBaP is a more physiological method than conventional pacemaker implantation, and its application will increase in the coming years. We propose a novel formula that predicts QTc in these patients.