Question: The two snap shots were taken 1 minute apart from a postoperative patient.What is the difference between the CVP traces in each of the panels?
Answer: A white arrow has been added to each panel to help identify the "a" wave in each trace.
Top panel (Clock time 13:44 Hrs) - Recorded with
A-pacing at 130 bpm. There is
Atrio-ventricular synchrony. "a" wave is small (& is smaller than the "v" wave). Mean CVP is 7 mmHg. Arterial BP 92/46 (mean 64) mmHg.
Bottom panel (Clock time 13:45 Hrs) Again, the white arrow identifies the "a" wave. Comparatively, these are
"giant" a waves. A-pacing is stopped. Patient's
native rhythm is accelerated junctional rhythm at 104 bpm.
AV synchrony is lost - atria are contracting against a closed AV valve causing "giant" a waves. Now, the CVP is 9 mmHg (higher than when there was AV synchrony) and arterial BP is lower (73/33, mean 46 mmHg) - emphasizing the importance of AV synchrony in this patient.
Note:
"Cannon" a waves are occasional giant a waves seen in patients with complete AV block. In this situation, a waves are normal or close to normal during several beats when there is apparent AV synchrony by shear coincidence of a sequential atrial and ventricular contractions. But, there will be occasional sudden appearance of one giant a wave at variable intervals when apparent AV synchrony is lost.
