What is a key difference between atrial flutter and atrial fibrillation?

Atrial flutter is characterized by organized electrical activity in the atria, which results in a well-defined pattern seen on an electrocardiogram (ECG), typically presenting as "sawtooth" waves known as F-waves. This organized activity allows for a more predictable and regular rhythm. In contrast, atrial fibrillation exhibits chaotic and disorganized electrical activity, leading to a rapid and often irregular heart rate without distinct F-waves. This fundamental difference in the organization of atrial electrical activity is vital for distinguishing between the two conditions clinically and on an ECG.

The other options do not accurately reflect the primary distinctions between atrial flutter and atrial fibrillation. For instance, while atrial flutter can present at a faster rate, atrial fibrillation can also occur at high rates and is not necessarily slower. The waveform characteristics in terms of QRS complexes do not typically differ markedly between the two conditions; both can have narrow QRS complexes in the absence of any bundle branch blocks. Finally, both conditions can occur in a range of ages; atrial flutter is not exclusively seen in younger patients.