Final answer:
The most likely diagnosis based on the given ECG is Atrial Fibrillation with Premature Atrial Contractions (PACs) (A).
Step-by-step explanation:
An electrocardiogram (ECG) is a graphical representation of the electrical activity of the heart. In atrial fibrillation, the electrical pattern prior to the QRS complex is abnormal, and the frequency between the QRS complexes is increased. Premature atrial contractions (PACs) are irregular heartbeats that originate in the atria, causing an extra beat.
In the given ECG, the electrical pattern is abnormal, there is no correlation between atrial activity (the P wave) and ventricular activity (the QRS complex), and there are additional premature atrial contractions (PACs). These features are consistent with atrial fibrillation with PACs.
So, the answer is A.