Effects of transcutaneous cardiac pacing on ventricular repolarization and comparison with transvenous pacing.

BACKGROUND: The electrocardiographic (ECG) effects of transcutaneous cardiac pacing (TCP) on ventricular repolarization have not been studied in detail. This study evaluated the influence of TCP on ventricular repolarization. The results were compared with those obtained by conventional transvenous right ventricular pacing (TVP).

METHODS: Sixty-two patients with spontaneous bradycardia and standard indication for pacemaker or implantable cardioverter-defibrillator implantation were enrolled. Patients were divided into two groups based on the presence or not of structural heart disease (SHD). Surface 12-lead ECG characteristics of ventricular depolarization (QRS complex) and repolarization (QT and JT intervals, Tpeak to Tend interval [TpTe], QT dispersion [QTd], TpTe dispersion [TpTe-d], and TpTe/QT ratio) were recorded at baseline before device implantation (45 ± 5 beats/min) and were compared with corresponding data during short periods of TCP and TVP at a similar increased heart rate (81 ± 6 beats/min).

RESULTS: Both TCP and TVP compared with baseline measures significantly increased the QRS complex and the QTc/JTc intervals regardless of SHD status (P < .001), and QTc-d and TpTe particularly in the patients without SHD (P < .05). TCP caused greater QRS prolongation than TVP in patients without SHD (P < .05), but it was associated with lower TpTe and TpTe/QT in patients without SHD as well as lower QTc-d in patients with SHD (P < .05).

CONCLUSION: TCP produces greater lengthening of ventricular repolarization than TVP, but lesser increase of ECG markers of ventricular dispersion of repolarization.