What effect does atrial fibrillation typically have on the cardiac output?

Atrial fibrillation typically leads to a decrease in cardiac output primarily due to the loss of the atrial kick. In a normal heart rhythm, the atria contract in a coordinated manner to fill the ventricles with blood before they contract. This atrial contraction adds an important volume of blood to the ventricles, referred to as the 'atrial kick.'

In atrial fibrillation, the atria are not contracting effectively; instead, they quiver or fibrillate asynchronously. This disrupts the coordinated filling of the ventricles and significantly reduces the efficiency of blood being pumped out of the heart. The resultant decrease in the volume of blood ejected with each heartbeat can lead to a reduced overall cardiac output.

This condition may become more concerning in patients with existing heart issues or in higher heart rates, where the time available for the ventricles to fill is already limited, compounding the effect of the loss of the atrial kick. As such, the correct understanding of how atrial fibrillation impacts cardiac output involves recognizing the essential role of the atrial contraction in ensuring optimal heart function.