Acute live firefighting effects on ventricular-arterial coupling and pulsatile afterload in middle-aged firefighters

Firefighting increases afterload, leading to ventricular-arterial coupling mismatch in young firefighters that may contribute to coronary hypoperfusion and the elevated risk of on-duty cardiac events. Since this risk is higher with aging in firefighters, we examined their ventricular-vascular coupling and afterload responses to acute firefighting. Twenty-two male firefighters (40-59 years) performed 18-min high-intensity firefighting drills while wearing protective gear and breathing apparatus. Echocardiography was conducted before and within 10 min after firefighting to estimate cardiac volumes, while tonometry-derived pulse wave analysis estimated wasted pressure effort (Ew) and aortic reservoir function. Ventricular-arterial coupling was quantified using the arterial (Ea) to ventricular (Ees) elastance ratio, and coronary perfusion was estimated via the Buckberg index. Firefighting reduced stroke volume (difference (∆) = -17 mL, p < 0.001), Ew (∆ = -800 dyne cm^-2 s, p = 0.005), aortic reservoir function (∆ = -6.9%, p < 0.001), and Buckberg index (∆ = -0.28, p < 0.001). Firefighting augmented Ea/Ees (∆ = 0.10, p = 0.035) stemming from increases in Ea (∆ = 0.16 mmHg.mL^-1, p = 0.046) not counteracted by Ees. Heart rate changes were associated with Ew (r = -0.60, p = 0.017) and aortic reservoir function (r = -0.80, p < 0.001). Although middle-aged firefighters exhibited typical post-firefighting cardiovascular strain, including reduced coronary perfusion, the role of ventricular-arterial interactions and pulsatile afterload remains unclear due to heart rate confounding.