Abstract Body: Introduction: Transcutaneous pacing (TCP) is an emergent procedure used in the prehospital setting to treat hemodynamically unstable bradycardia. Prior studies have questioned the efficacy of prehospital TCP and highlighted its high mortality. Ideally, TCP results in electrical and subsequent mechanical capture to augment perfusion. Little is known about the frequency of either and their clinical consequences.
Methods: This is a retrospective cohort study of patients treated by a fire-based EMS agency with attempted TCP between April 2017 and February 2024. Defibrillator data, audio recordings, and medical records were reviewed. The primary outcome was electrical capture, defined as a widened QRS and T wave. When present, electrical capture was classified into periods of complete or intermittent capture (ventricular depolarization following 100-75% or 75-25% of pacing spikes, respectively). Other outcomes include potential indicators of mechanical capture: systolic blood pressure, provider-perceived pulse during TCP, and survival to hospital discharge.
Results: Of the 56 patients receiving attempted TCP, median age was 70 years, 34% were female, and 34% survived to discharge. CPR was administered in 59% of patients. Median attempted TCP time was 18.9 (Interquartile range [IQR] 7.6, 29.0) minutes. Electrical capture was achieved in 18 patients (32%), with complete capture achieved a median of 13.8% (IQR 1.7-60%) of attempted TCP time, and intermittent capture 1.9% (IQR 0-49%) of attempted TCP time. The median change in systolic blood pressure was +22.0 (IQR: -2.0, 81.5) mmHg in patients with electrical capture, and 0.0 (IQR: -29.0, 7.0) mmHg in those without. While attempting TCP, a palpable pulse was verbalized by providers 26 times across 19 patients; only 4 instances (15%) concurred with electrical capture. Survival to hospital discharge was greater in those with electrical capture (42% [3/7] versus 32% [10/31], p=0.78) than those without. This study is limited by its modest sample size, single agency location, and retrospective nature.
Conclusions: Attempted prehospital TCP produced poor rates of electrical capture. When achieved, electrical capture correlated with an increased SBP and a greater likelihood of survival. Perceived palpable pulses rarely corresponded to electrical capture, serving as a poor surrogate for mechanical and electrical capture. Further study is required to identify accurate, rapid, and objective means to assess TCP success.