What condition occurs when an electrical impulse is delayed while passing through the atria and AV node?

The condition characterized by a delay in the electrical impulse as it travels through the atria and the AV node is first-degree heart block. This occurs when there is a prolonged conduction time through the AV node but no missing beats. In first-degree heart block, every impulse from the atria reaches the ventricles, but the time it takes for the impulse to travel is longer than normal. This is typically indicated by a consistently prolonged PR interval on an electrocardiogram (ECG), which reflects this delay.

In contrast, second-degree heart block would lead to some impulses being completely blocked, resulting in intermittent missed heartbeats. Atrial fibrillation is a condition with rapid and disorganized electrical signals in the atria, leading to an irregular and often rapid heart rate. Sinoatrial block, on the other hand, involves the failure of impulses to be generated or transmitted from the sinoatrial node, resulting in missed heartbeats due to failure in the primary pacemaker.

Thus, the key feature of first-degree heart block – the delay in conduction without any lost beats – directly aligns with the described condition of an impulse being delayed while passing through the atria and AV node.