A 62-year-old man presented with palpitations. An analysis of his ECG found sinus rhythm at 83 bpm with premature atrial complexes, where every third P wave was premature in a pattern of trigeminy. The QRS complexes, ST segments, and T waves were normal with no signs of right or left atrial enlargement, bundle branch blocks, ventricular hypertrophy, or myocardial infarction. The final diagnosis was sinus rhythm with atrial premature complexes in a pattern of trigeminy, but an otherwise normal ECG.

1. Stepwise interpretation of ECG ID 352 –Sinus rhythm With premature atrial complexes

2. ID 352 – 62 year old man with palpitation

3. Can you see P waves? ID 352 – 62 year old man with palpitation

4. Yes – There is sinus rhythm with premature atrial complexes ( the P waves marked by an arrow ) Every 3 rd P is premature ( trigeminy ) - The sinus P waves show no evidence of right or left atrial enlargement ID 352 – 62 year old man with palpitation

5. Let’s now look at the QRS complexes: There is normal QRS axis (between 0 and 90 degrees) ID 352 – 62 year old man with palpitation

6. The QRS duration is normal : There is no right bundle branch block, left bundle branch block or non‐specific block ID 352 – 62 year old man with palpitation

7. There is no right ventricular hypertrophy or left ventricular hypertrophy ID 352 – 62 year old man with palpitation

8. There are no QRS signs of myocardial infarction –There are normal ST segment and normal T waves ID 352 – 62 year old man with palpitation

9. ID ID 352 – Final diagnosis: Sinus rhythm, 83 bpm, with atrial premature complexes in a pattern of trigeminy. Otherwise, a normal ECG.