Meet the top 10 most common arrhythmias in veterinary patients


This cheat sheet next to your ECG machine can cut down on your differential deliberation.

ECG readings in 4 steps

1. Get a heart rate.

2. Find a normal beat (P-QRS-T) on the ECG strip-“It's easy because it's alphabetical,” jokes Church.

3. Compare all the other beats to what you think is normal.

4. Determine whether the QRS interval is using the His-Purkinje system (fast) or conducting cell-to-cell (slow).

More on His-Purkinje from Church: The His-Purkinje are the nerves of the heart. Cell-to-cell conduction relies on gap junctions so one cell can talk to the cells next to it and pass the message onward. That obviously takes longer, so the QRS complex looks wider on the ECG. Typically, if the QRS involves the His-Purkinje, then it is narrow and comes from the atrium, and if the QRS is wide, it comes from the ventricle.


At CVC San Diego, Whit Church, DVM, DACVIM (cardiology), a veterinary cardiologist at Desert Veterinary Medical Specialists in Gilbert, Arizona, delivered a quick list of the top 10 causes of arrhythmias you'll see during an electrocardiographic examination. Church's advice: Post this list by your ECG machine, and you'll be whittling away your rule-outs in no time flat-and avoiding the flatlining, of course.

First, Church says you can cut the top 10 in half based on the patient's heart rate. If the rate is < 70 beats/minute, you know you're dealing with a bradyarrhythmia. If the heart rate is above 160 to 180 beats/minute, look to the top 5 tachyarrhythmia rule-outs.

With no further ado, here are the top 10:


1. Sinus bradycardia

2. Atrioventricular block

Third-degree atrioventricular block. (Figures courtesy of Dr. Whit Church)


3. Sick sinus syndrome

4. Atrial standstill

5. Persistent atrial standstill



1. Sinus tachycardia

2. Ventricular tachycardia

Ventricular tachycardia


3. Supraventricular/atrial tachyarrhythmia

Supraventricular tachycardia


4. Atrial fibrillation

Atrial fibrillation


5. Atrial flutter

Another bonus on the tachyarrhythmia list is that atrial flutter is uncommon, says Church, so you usually have only four conditions to consider.

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