The ventricular response (VR) during atrial fibrillation (AF) presents particular characteristics which may play a relevant role in the selection of the most appropriate treatment. Preferential AV nodal conductions are visible when RR intervals Poincare plots during AF are constructed. The main objective of this work is the evaluation of the relationship between the position of more probable RR intervals and the atrial rate (AA). Holter monitoring was used to demonstrate that in patients with one, two or even three clusters of RR intervals, these clusters track nth multiples of the atrial rate (i.e. 2ldrAA, 3ldrAA, etc.). A possible classification of AF patients according to the ventricular response mechanism could help to improve the rate control treatments results.