Pressure waveform changes with a junctional rhythm

The initial rhythm in panel A is junctional and the P waves are superimposed on the QRS complex, resulting in simultaneous atrial and ventricular contraction and giant "v" waves on the right atrial (RA) pressure tracing due to atrial contraction against the closed tricuspid valve. With resumption of sinus rhythm, the RA pressure becomes normal with an "a" wave that is taller than the "v" wave. There is also a change in the right ventricular pressure waveform. The initial rhythm in panel B is junctional and the RV pressure is 38 mmHg. With resumption of sinus rhythm (end of panel B) and the restoration of atrial contribution to RV filling, the RV pressure increases to 50 mmHg.