The ECG shows a repeating pattern of four beat groupings. In the first three beats of each group beat, the QRS complexes are wide and followed by retrograde P waves that come after the QRS, suggesting the beats start near the AV node (junctional tachycardia). The wide QRS complexes are due to underlying Left Bundle Branch Block (LBBB). The fourth beat in each group looks different, comes earlier than expected, and doesn't have a P wave after it, which indicates a Premature Ventricular Contraction (PVC).