Final answer:
Atrial fibrillation is characterized by an abnormal electrical pattern on an ECG, including an increased frequency between the QRS complexes, indicating a rapid and irregular heart rate.
Step-by-step explanation:
When assessing a client with atrial fibrillation, one would expect to find an abnormal electrical pattern prior to the QRS complexes on an electrocardiogram (ECG). This abnormal electrical pattern is characteristic of atrial fibrillation. Additionally, one would also expect to observe an increased frequency between the QRS complexes on the ECG. This indicates a rapid and irregular heart rate.