Ectopic atrial rhythm at a rate of 75 beats per minute. P waves are clearly seen and negative in several leads, indicating they do not originate from the sinus node but likely a low atrial region. There is also an incomplete right bundle branch block present as shown by a widened QRS duration of 100 milliseconds with an rSR' pattern. The final diagnosis is an ectopic atrial rhythm at a rate of 75 beats per minute with an incomplete right bundle branch block.

1. Stepwise interpretation of ECG ID 419

2. ID 419 – What is your ECG diagnosis?

3. ID 419 – What is your ECG diagnosis? Do you see P waves? If you do, are they normal sinus P waves?

4. ID 419 – Ectopic atrial rhythm, 75/min. P waves are clearly seen. They are negative in II, III, aVF and V4-V6. They are not from the sinus node. They are not junctional (the PR interval is 180 msec., in junctional rhythm the PR is usually < 120 msec) They are most likely from a low atrial region (ectopic atrial rhythm )

5. ID 419 – Ectopic atrial rhythm, 70/min. Incomplete right bundle branch block The QRS axis is normal – The QRS duration is 100 msec., with a rSR’ pattern (incomplete right bundle branch block).

6. ID 419 – Final diagnosis: Ectopic atrial rhythm, 75/min. Incomplete right bundle branch block There are no signs of ventricular hypertrophy – No QRS signs of myocardial infarction- The ST segment and T waves are normal.