Final answer:
The most likely diagnosis for an ECG showing a normal rhythm interrupted by premature ventricular contractions every other beat is Sinus Rhythm with Ventricular Bigeminy.
Step-by-step explanation:
The diagnosis of an ECG can vary based on the patterns observed in the electrical activity of the heart which is indicative of different types of cardiac arrhythmias. For a proper diagnosis, the ECG must be correlated with both symptoms and a thorough understanding of cardiac rhythms. Based on the standard definition of rhythms, the most likely diagnosis for an ECG showing a normal sinus rhythm with every other beat being a premature ventricular contraction (PVC) would be Sinus Rhythm with Ventricular Bigeminy. Ventricular Couplets would appear as two consecutive PVCs, which is not the rhythm described. Atrial Fibrillation would show an irregularly irregular rhythm with no distinct P waves, and Supraventricular Tachycardia would display a fast heart rate originating above the ventricles, usually with a regular rhythm which doesn't typically include PVCs as a feature. An ECG showing regular operation of the sinoatrial node with occasional PVCs would fit the description of a Sinus Rhythm with Ventricular Bigeminy.