Transcutaneous Pacing in the Prehospital Setting – A Retrospective Cohort Study of Electrical Capture

Transcutaneous pacing (TCP) treats hemodynamically unstable bradycardia refractory to pharmacologic management. Effective TCP requires electrical and mechanical capture to augment perfusion. Little is known about prehospital TCP and capture incidence. We conducted a retrospective cohort study of patients treated with prehospital TCP by an emergency medical services agency between 2017 and 2024. Continuous ECG recordings from cardiac monitors were reviewed. Electrical capture was the primary outcome, defined as a widened QRS with a distinct T wave following a TCP spike. Secondary measures included capture duration, clinician-verbalized pulse during pacing, plethysmograph waveform alignment, and changes in systolic blood pressure (SBP), pulse oximetry, and end-tidal carbon dioxide. Fifty-six patients received attempted TCP. Median age was 70 years (interquartile range [IQR] 58-85), and 34% were female. Cardiopulmonary resuscitation (CPR) was administered in 59% of patients. Electrical capture was achieved in 18 patients (32%). Among patients who achieved electrical capture, complete capture occurred a mean of 27.2% (standard deviation 30.5%) of attempted pacing duration. The median SBP change was +22.0 (IQR: -2-82) mmHg in patients with electrical capture and 0.0 (IQR: -29-7) mmHg in those with only rare-to-absent capture (p = 0.031). During TCP, clinicians verbalized a palpable pulse 26 times across 19 patients. Only 4 instances (15%) coincided with electrical capture. Electrical capture during prehospital TCP occurred in a minority of patients and was often intermittent. Prehospital identification of mechanical capture using routine clinical indicators was difficult and unreliable. Future work should standardize capture definitions and physiologic measurements to determine when TCP produces clinically meaningful perfusion.