Why prevention of RVP may not always be the best option. Paper speed 25 mm/s. In a patient with a dual-chamber pacemaker, atrial pacing is followed by an intrinsic QRS complex after an AV delay of 480 ms, permitted by a special algorithm. This causes the P wave almost to overlap with the preceding T wave. Haemodynamically, this can be equivalent to VVI pacing with retrograde VA conduction causing pacemaker syndrome and a reduction in cardiac output.