What arrhythmia is characterized by multiple ectopic foci in the atria leading to an irregularly irregular rhythm?

The arrhythmia characterized by multiple ectopic foci in the atria, leading to an irregularly irregular rhythm, is atrial fibrillation. In this condition, chaotic electrical signals originate from various areas within the atria, which results in the atria contracting in an uncoordinated manner. This not only leads to an irregular heart rhythm but also frequently results in varying heart rates. As a consequence of this disorganized activity, the rhythm is commonly described as "irregularly irregular," and this distinguishes atrial fibrillation from other arrhythmias.

In contrast, atrial flutter typically has a more organized rhythm characterized by a single ectopic focus producing rapid, regular atrial contractions. Ventricular tachycardia is primarily a rapid rhythm originating in the ventricles rather than the atria, while ventricular fibrillation is a chaotic and life-threatening rhythm that also occurs in the ventricles. These characteristics help clarify why atrial fibrillation is the specific condition that fits the description provided in the question.