Page 83 - Rapid Review of ECG Interpretation in Small Animal Practice, 2nd Edition
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Answer 21 ECG Cases
Answer 21
VetBooks.ir 1 ECG 21 shows accelerated idioventricular rhythm.
• This rhythm occurs when the discharge rates of the sinus node and another ectopic pacemaker site
(nodal or ventricular) approximate each other. In this example, when the sinus rate is slightly slower
than the ventricular rate, the ventricular rate “takes over.” The R–R interval of the sinus complexes
(blue arrow) is 460 ms (heart rate of 130 bpm) and the interval of the ventricular complexes (black
arrow) is shorter at 420 ms (143 bpm). Therefore, the ventricular rate is “accelerated” and becomes
the dominant rhythm until the sinus rate increases and recaptures control of the heart rate later in the
strip. This arrhythmia is commonly seen in patients under anesthesia or animals with significant
systemic disease.
• Generally, no therapy is required as the sinus and ectopic pacemaker rate approximate each other.
Usually, slow ventricular rhythms do not result in hemodynamic consequences and are not a
significant risk for degeneration into ventricular fibrillation; however, if the ventricular rate is very
fast (typically >180 bpm), antiarrhythmic treatment may be necessary.
21 I
II
III
aVR
aVL
aVF
70
