What rhythm is commonly associated with an irregular heartbeat?

Atrial tachycardia is a type of arrhythmia that originates in the atria, which often leads to an irregular heartbeat. This condition is characterized by how the electrical signals are generated and propagated in the heart. When these signals become abnormal, they can cause the heart to beat rapidly and irregularly.

In contrast, sinus rhythm and normal sinus rhythm indicate a regular heartbeat, generated by the heart's natural pacemaker, the sinoatrial node. These rhythms are typically regular and indicate proper heart function. Ventricular tachycardia, while also an abnormal rhythm, usually involves the ventricles and can lead to serious complications, including reduced blood flow to the body, but it does not specifically highlight irregularity in the same way that atrial tachycardia does.

Thus, the link between atrial tachycardia and an irregular heartbeat makes it the most appropriate choice in this context.