What percentage of ventricular filling is lost due to acute atrial fibrillation?

In cases of acute atrial fibrillation, the loss of coordinated atrial contraction impacts ventricular filling significantly. The correct answer reflects that approximately 15-25% of ventricular filling is compromised due to the absence of effective atrial contraction. This reduction occurs because the atria are unable to contract efficiently, leading to a decrease in the volume of blood that can be pushed into the ventricles during the diastolic phase of the cardiac cycle. During normal sinus rhythm, the atrial contractions contribute to enhanced ventricular filling through a mechanism often referred to as "atrial kick." However, in atrial fibrillation, this is lost, causing the ventricles to depend more on passive filling from venous return, resulting in reduced cardiac efficiency.

The other percentage ranges either underestimate or overestimate the impact of acute atrial fibrillation on ventricular filling. Understanding these dynamics is crucial for assessing cardiac function and could have implications for treatment and management of patients experiencing this arrhythmia.