In AF why the ventricular rate is irregular?

Here is a case report from Dr. Brugada’s group. What is your diagnosis? Source & Courtesy Sergio Richter, Joseph Brugada et all , 100(1), 154–156. doi:10.1016/j.amjcard.2007.02.067 Whoever diagnosed AF in the above ECG need not feel bad. The rhythm is not AF, though it mimics very closely. In cardiology, especially in electrophysiology, we can get surprises on a daily basis. (Read below) Why the ventricular rate is irregular in AF? Atrial fibrillation (AF)  may sound like a  simple clinical arrhythmia until we ask this delicate question. The traditional and fairly accepted answer is that, AV node with all its collective decremental property filters the incoming atrial impulses (Which varies 400-600/mt) in a random fashion and allows only about 1/3rd of impulses. So, technically it is  AV block of various degrees that makes the ventricular response irregular. Any other explanation possible? How about AV node playing out a silent game with Atria, deciding to block everything and start its own fast escape rhythm, rather than leaking out selectively atrial impulses. Some think this is fictional, some others feel it can be real too. When this happens it can be referred to as irregular junctional tachycardia or AF with varying AV blocks. It has been tough, to prove it is only the atrial impulses penetrating through the AV node complex and exiting on the ventricular side unscathed? Understanding AV node is not easy  AV node morpholo...
Source: Dr.S.Venkatesan MD - Category: Cardiology Authors: Tags: Atrial fibrillation Cardiology Patho physiology Infrequently asked questions in cardiology (iFAQs) AV node anatomy AVNRT and AF Dual AV nodal path way poly av nodal pathway Pseudo atrial fibrillation Source Type: blogs