I am posting the answer earlier than I am supposed to, since this a very hard ECG to diagnose and its purpose is educational and not to test you knowledge. And the answer is (I have created an edited image so that it is better understandable): Patients who have undergone heart transplant have the remaining atria from the "old" heart which beat separately from the new heart. The purpose of this quiz is to make notice that we have to study the ECG and not just to remember patterns that we look for each time. So if you look carefully you can see that there is always a P wave preceding the QRS complex, with a stable PR which is actually prolonged(1st degree AV block). You can also notice the other wave which is completely autonomous and if you think of the QRS complex and those P waves I mentioned above disappear you can see that this (remaining) wave has a stable frequency and that it has a morphology consistent with an atrial wave (P wave). Of course a situation where you will have to diagnose such an ECG is purely theoretical since most patients with heart transplant will mention it in their history
Yes there is RBBB, keep in mind that this is a transplanted heart which may have many conduction defects. I didn't mention it, since the purpose of this post is to show you how the ECG of a patient undergone heart transplant is usually like. The RBBB could be of significance if it is a new finding during the follow up of the patient.
Check out how it looks like: http://img.medscape.com/pi/emed/ckb/clinical_procedures/429035-429816-1973.jpg also check out these links about the ECG in heart transplantation: http://www.wikidoc.org/index.php/The_EKG_of_cardiac_transplantation http://www.nejm.org/doi/full/10.1056/NEJM200105173442005
