three fates of PAC's

As illustrated, PAC's can have three fates: PAC-1enters the ventricles and encounters no conduction delays, therefore causing a narrow QRS; PAC-2 occurs a little earlier and can't get through the AV junction, therefore beingnonconducted; PAC-3 seen inlead V1 makes it into the ventricles but encounters the right bundle refractory period, therefore conducting with a RBBB morphology; i.e. aberrant conduction.