Structural Heart Abnormalities are Prevalent on the 12-lead ECG among Volunteer Firefighters

Published

April 1, 2025

Author(s)

Alexander Bae, Chi-Ju Lai, Yichen Yu, Nicole Krupa, David Hostler, Wai Cheong Tam, Mary Carey, Wendy Brunner, Dillon Dzikowicz

Abstract

Introduction: In the US, the most common cause of death among active-duty firefighters is sudden cardiac death (SCD). Underlying heart diseases are important propagator of ventricular tachyarrhythmias that cause SCD. The objective of this abstract is to assess the incidence of underlying heart disease, identified on 12-lead electrocardiograph (ECG), that may place firefighters at greater risk of SCD. Methods: We digitalized 12-lead ECGs recorded among firefighters who visited a firefighter health screening program at least 4 times from 2011-2019. We extracted the interval measurements (Heart Rate, T-axis, QRS-axis, QRS duration, QTc duration) and interpretation statements from each of the 12-lead ECGs and grouped potential propagators of ventricular tachyarrhythmias including left ventricular hypertrophy (LVH), coronary artery disease (CAD), and cardiac conduction disease. We used simple mean imputation to handle missing data. Descriptive statistics including means and frequencies were used to analyze the sample. Results: Among 465 firefighters (90.1% male) with a mean age of 47.1 (±13.6) whom 1,296 12-lead ECGs were analyzed, 21.5% (n=278) of Heart Rate, 0.39% (n=5) T-axis, 26.4% (n=342) QRS-axis, 40.0% (n=518) QRS duration, 5.40% (n=70) QTc duration were abnormal. In addition to intervals, the 12-lead ECGs generated 1,970 interpretation statements of which 28.2% (n=555) were deemed possible pathoanatomical substrates including 3.1% (n=34) LVH, 24.7% (n=137) CAD, and 69.2% (n=384) cardiac conduction diseases. Among cardiac conduction diseases, intraventricular conduction disease was the most prevalent (n=204, 36.8%), followed by vertical axis (n=70, 12.6%), right bundle branch block (n=59, 10.6%), left anterior fascicular block (n=34, 6.1%), and left bundle branch block (n=17, 3.1%). Interestingly, we did not observe a temporal relationship regarding the number of pathoanatomical substrates over the screening period. Conclusions: Nearly 30% of the interpretation statements generated from 12-lead ECGs were indicative of possible pathoanatomical substrates that cause SCD, which reflects the apparently negative effect of fire suppression activity on one's cardiopulmonary health. Our result justifies the imperative need of effective prevention method for cardiac conduction diseases among firefighters. Further research is needed to collect 12-lead ECG systematically amongst other measures such as diet and BMI which reflect work culture and lifestyle of firefighters.

Citation

Journal of Occupational and Environmental Medicine

Pub Type

Journals

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Keywords

Sudden cardiac death, Firefighting, Electrocardiogram

Citation

Bae, A. , Lai, C. , Yu, Y. , Krupa, N. , Hostler, D. , Tam, W. , Carey, M. , Brunner, W. and Dzikowicz, D. (2025), Structural Heart Abnormalities are Prevalent on the 12-lead ECG among Volunteer Firefighters, Journal of Occupational and Environmental Medicine, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958179 (Accessed March 16, 2026)