This is the second column in a series discussing the number-one cause of firefighter line-of-duty deaths (LODDs): sudden cardiac death. To review the previous column (April 2009), firefighters are at a higher risk of cardiac death than the general public. The most strenuous physical activities, including fire suppression and physical training, have the highest risk of cardiac death. Additionally, responding to and returning from alarms also has a higher risk of cardiac death, while non-emergency duties, EMS and non-fire responses did not have a higher risk of cardiac death. To completely understand this problem, what it is about these activities that put firefighters at such a high risk of cardiac death must be explored.

Anyone who puts on bunker gear and self-contained breathing apparatus (SCBA) and drags a charged line up a flight of stairs knows how physically demanding firefighting is. It has been well documented that firefighting, in particular fire suppression, requires firefighters to operate at maximal levels of exertion. The American Heart Association classifies firefighting as the most intense category. Firefighters must perform at the highest level of cardiovascular function.

Firefighters experience an immediate dramatic increase in heart rate and blood pressure in response to the receipt of an alarm. This is due to the "fight-or-flight response," which is that rush of adrenaline firefighters get when the alarm comes in. A sharp increase in blood pressure could provoke a heart attack, which would explain why firefighters are at a higher risk of cardiac death while responding to or returning from alarms.

It is also well known that physical activity can provoke heart attacks and sudden cardiac death. This helps explain why firefighters are at a higher risk of cardiac death than the general public. The high stress and physical workload that firefighting places on a firefighter's cardiovascular system may precipitate a heart attack. Recent medical research shows that firefighters who died of cardiac deaths had pre-existing cardiovascular disease after review of their medical records in these LODDs. All of the firefighters that died of cardiovascular disease had major modifiable risk factors for cardiovascular disease.

These studies have shown that age greater than 45, smoking, previous diagnosis of cardiovascular disease and high blood pressure are strong risk factors for cardiovascular disease and sudden cardiac death in firefighters. Elevated cholesterol levels were found to be a strong indicator of cardiovascular disease in firefighters, but not of sudden cardiac death.