Quiz #22: ICU monitor interpretation - Answers

5 month old baby. Postoperative day 1 after closure of membranous VSD. Panel 1 and Panel 2 were recorded few minutes apart.

(Click on the image to enlarge)

1.       What is the arrhythmia in Panel 1?

a.       JET (This patient already on Amiodarone. Therefore, JET rate is lower than usual)

2.       What type of pacing is done in Panel 2?

a.       Atrial pacing

3.       Describe the important difference between the CVP waveform in Panel 1 and Panel 2. What is the reason for the difference?

a.       “Giant” a-waves in Panel 1.

b.      Mechanism: Atrial contraction against closed AV valve. Junctional beat gets transmitted both atrium and ventricle. P wave is embedded inside the QRS. Both atria and ventricles contract at the same time, leading to atrial contraction against a closed AV valve (Ventricular contraction causes AV valves to close).

c.       Giant a-waves vs. Cannon a-waves: Strictly speaking, these two entities are different. In junctional rhythm, “Giant a-waves” are present in every beat. In contrast, “Cannon a-waves” are noted in complete AV block where P wave to QRS relationship is not 1 to 1. Some P wave happen to precede QRS. Therefore, some atrial contractions occur with AV valve open. Only occasional P waves conflict with QRS complexes causing atrial contraction with closed AV valve. Therefore, large a-waves are noted only in some beats…similar to a cannon firing only intermittent. Cannon needs to be packed with gun powder after each firing!

4.       Comment about AV conduction in Panel 2.

a.       Apparently, prolonged PR interval (First degree AV block). “Apparently” because actual measurements are not possible from these images.

5.       Why does arterial line trace have a “flat top”? How will you rectify this issue?

a.       Upper limit of the display-scale for arterial line is set at 90 mmHg. But, systolic BP is 99. This is rectified by either increasing the upper limit of display-scale or “auto adjust” mode on the monitor.