Acute live firefighting causes ventricular-vascular coupling mismatch but reduces pulsatile afterload

Background: Firefighting reduces left ventricular systolic and diastolic function and increases arterial load. The resultant ventricular-vascular coupling mismatch underlies a reduced cardiac performance. Such firefighting-induced changes resembling the cardiac fatigue phenomenon are hypothesized to contribute to the greater risk of firefighters for cardiovascular events immediately following fire suppression activities. However, whether cardiac performance is compromised following acute firefighting exposure (<20 min) is unknown. Purpose: We test the hypothesis that cardiac performance would be reduced after short-term acute live firefighting. Methods: Twenty-one middle-aged male firefighters (40-59 years) completed 18-min of high-intensity, live firefighting exercises while wearing personal protective equipment and self-contained breathing apparatus. Echocardiographic measurements were obtained before and within 10-min after firefighting to estimate cardiac volumes (i.e., M-mode), mitral inflow velocities (i.e., Doppler) and myocardial motion (i.e., tissue Doppler). Tonometry-derived pulse wave contour analysis was conducted to estimate end-systolic pressure (ESP), and pulsatile afterload via the wasted pressure effort metric (Ew). Heart-vasculature interactions were quantified via the arterial (i.e., ESP/stroke volume) to ventricular elastance (i.e., ESP/end-systolic volume) coupling ratio (Ea/Ees). Firefighting-induced changes in cardiac performance were tested with paired t -tests. Results: Firefighting reduced stroke volume (difference (Δ)= -17 mL, 95% CI: -26 to -8 mL, p <0.001), ejection fraction (Δ= -3.6%, 95% CI: -7.0 to -0.3%, p =0.032), peak E (Δ= -12 cm.s-1, 95% CI: -17 to -6 cm.s -1 , p <0.001) and lateral peak e’ (Δ= -9 cm.s -1 ; 95% CI: -12 to -7 cm.s -1 , p <0.001) velocities. Conversely, firefighting augmented Ea/Ees (Δ=0.10, 95% CI: 0.01 to 0.20, p =0.035) due to an increase in Ea (Δ= 0.16 mmHg.mL -1 , 95% CI: 0.03 to 0.32 mmHg.mL -1 , p =0.046) not counteracted by Ees (Δ= -0.12 mmHg.mL -1 , 95% CI: -0.27 to 0.52 mmHg.mL -1 , p =0.526). Ew was reduced after firefighting (Δ= -804 dyne-s-cm −2 , 95% CI: -1333 to -275 dyne-s-cm −2 , p =0.005). Conclusions: Althoughacute firefighting produced changes consistent with cardiac fatigue including ventricular-vascular coupling mismatch and depressed diastolic function, it also reduced pulsatile afterload. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.