Case Studies In Small Animal

Cardiovascular Medicine

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ECGs

Case 35

Event monitor

ECG recorded at 25 mm/sec

The square wave toward the middle of the top trace shows when the owner hit the button on the event monitor at the time she noted he was starting to have problems. During the top trace and the first 4 complexes of the second trace Dante was having a high grade second degree AV block with a heart rate around 35 beats/minute. At the end of the second trace and probably until the last two complexes of the third trace he is in third degree AV block. At the end of the second trace and the very beginning of the third trace his AV node doesn't conduct and he has no escape focus that works. This results in abut a 4 second period of no ventricular activity. It generally takes 6 to 8 seconds of no ventricular activity to make a dog lose consciousness. Consequently, all Dante did was become weak enough to collapse.

Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.