It happens less often in more recent models of dual chamber pacemakers due to the addition of a ventricular blanking period, which coincides with the atrial stimulus.
This helps to prevent ventricular channel oversensing of atrial output.
Crosstalk is more common in unipolar systems since they require a larger pacing spike.
In some cases, crosstalk can occur in the pulse generator circuit itself, though more common causes include atrial lead dislodgement into the ventricle, ventricular lead dislodgement into the atrium, high atrial output current, high ventricular sensitivity, and short ventricular blanking period.
[1] In general, the treatment of crosstalk includes decreasing atrial pacing output, decreasing atrial pulse width, decreasing ventricular sensitivity, increasing the ventricular blanking period, activating ventricular safety pacing, and new atrial lead implant if insulation failure mandates unipolar programming.