The electrocardiogram of ventricular capture during transcutaneous cardiac pacing

Transcutaneous cardiac pacing (TCP) is deeply entwined with the problem of assessing ventricular capture on the electrocardiogram (ECG). We sought clarification of ventricular capture during TCP. We studied one hundred and ten patients (75 ± 12 years) with bradycardia who underwent pacemaker or implantable cardioverter-defibrillator implantation. The cohort was stratified by structural heart disease (SHD) status and presence of narrow or wide QRS during spontaneous heart rhythm. We compared 12-lead ECG data at baseline (48 ± 7 beats/min) with those of TCP as well as of transvenous pacing (TVP) at a similar increased heart rate (76 ± 9 beats/min) to ensure constant ventricular capture. The QT interval was corrected for heart rate (QTc) using Bazett's method as well as by the Hodge's and Rautaharju's formulae depending on the presence of narrow or wide QRS at baseline. Electromechanical coupling was assessed by noninvasive arterial pressure measurement. TCP (median 80 mA) produced a QRS pattern resembling left bundle branch block. Overall, both TCP and TVP induced significant QRS and QTc prolongations when compared with baseline measures (p