Vascular and central hemodynamic changes following exercise-induced heat stress

Area of Science:

• Cardiovascular Physiology
• Environmental Extremes
• Exercise Science

Background:

• Occupational heat stress poses risks to cardiovascular health.
• Firefighters face significant exercise-induced heat stress (EIHS) due to protective gear.
• Understanding EIHS effects on hemodynamics and coronary perfusion is crucial for safety.

Purpose of the Study:

• To investigate the impact of EIHS on vascular function and central hemodynamic load.
• To assess changes in coronary perfusion indices under heat stress conditions.
• To determine if EIHS affects aortic stiffness and myocardial work.

Main Methods:

• 12 healthy men underwent 100 minutes of intermittent exercise in two conditions: heat stress (HS) with firefighter PPE and no heat stress (NHS) with cooling.
• Vascular-hemodynamic measures, including aortic blood pressure, reflected wave pressure (Pb), systolic (SPTI) and diastolic pressure time-integral (DPTI), and aortic stiffness, were recorded pre- and post-exercise.
• Pulse wave velocity was also assessed.

Main Results:

• SPTI was significantly greater, while DPTI and Pb were significantly lower post-exercise in the HS condition compared to NHS.
• No significant differences in pulse wave velocity or aortic stiffness were observed between conditions.
• EIHS led to increased indices of myocardial work and reduced indices of coronary perfusion.

Conclusions:

• EIHS does not alter aortic stiffness but increases myocardial workload.
• Reduced coronary perfusion indices under EIHS may be linked to heart rate responses.
• A potential mismatch between myocardial oxygen demand and supply during EIHS could increase cardiac vulnerability to ischemia.