The correct answer is 2:1 atrioventricular block with a left cranial axis deviation. Relevant Findings: Calculation of the heart rate shows a slow rate for a cat in the hospital as normal in-hospital heart rates for cats are 160 to 220 bpm. In evaluating the rhythm, each QRS complex has a P wave in front of it with an appropriate PQ interval, suggesting each QRS occurred after atrioventricular conduction. In evaluating the T waves, there are abnormal deflections at the end of each T wave that likely represent an extra (blocked) P wave. The spacing of these extra waves is exactly in sync with the P waves seen in front of each QRS complex, this infers a diagnosis of 2:1 atrioventricular block as there are two P waves present at a constant rate for each QRS. Therefore, the atrial rate is 200 bpm, which is appropriate for a cat, while the ventricular rate is exactly half that at 100 bpm. In addition to the slow heart rate, the QRS complexes do not appear normal for a cat as the QRS in leads II and III are negative. The positive QRS in lead I with progressively negative S waves in leads II and III suggest a deviation in the mean electrical axis, now directed toward the left cranial quadrant. This axis deviation is seen occasionally in cats with left ventricular hypertrophy or with disease of the left anterior fascicle. Given the concurrent AV block, the altered QRS axis in this cat suggests there is also disease of the distal conduction system – the left anterior fascicle in particular. View an annotated image of Sam’s ECG highlighting the relevant findings.