High-resolution 12-lead electrocardiograms of on-duty professional firefighters: a pilot feasibility study

Cardiovascular deaths among on-duty firefighters are high--double that of police officers and quadruple that of first responders. The aim of this pilot study was to establish the feasibility of obtaining high-resolution electrocardiograms (ECGs) of on-duty firefighters useful for detecting ECG predictors for cardiac events.

Twenty-eight professional firefighters (age, 46 ± 6 years) wore a 12-lead ECG Holter for 24 hours (16 hours while on duty and 8 hours postduty). All activities, including fire and medical calls, were monitored.

On average, the recordings were 92% analyzable. All were in the sinus, with a heart rate of 80 ± 11 beats per minute (range, 35-188 beats per minute). The average rr50 over the 24-hour Holter study was 6.2% ± 6% (range, 1%-23%) and the average square root mean square successive differences (RMSSD), NN intervals was 81 ± 55 (range, 24-209). Using the QRS/Tsimple formula, the average spatial QRS-T angle was 104° ± 17° (range, 78°-132°). Nonsustained ventricular tachycardia occurred irrespective of activity or time of day in 3 (11%) firefighters, which was significantly higher than in comparable normal populations (P < .05).

This preliminary work demonstrates that it is feasible to obtain high-resolution ECGs during firefighting activities and further points to the high prevalence of dysrhythmias among firefighters. The strategy of continuous field monitoring of firefighters could provide new insight into the association between their specific professional lifestyle and high cardiac risks.