''Courtesy of W.K. Lagrand and P.G. Postema, The Netherlands''<br />
A 53 year old woman has had mitral and tricuspid valve repair. An ECG is recorded. No P waves are seen before QRS complexes. She has temporary atrial pacemaker leads and a recording is made from these leads (recorded as V1 in the second ECG). Now it is evident that a junctional rhythm is present with retrograde P waves. A very long PQ interval is a differential diagnosis, but less likely.