Chapter 6 Supraventricular arrhythmias

Question 1

ECG characteristics of supraventricular prematures complexes (SVPCs)

Answer 1

1. Normal QRS morphology
2. QRS duration is < 0.07 sec
3. QRS complexes are seen to occur prematurely
4. P waves may or may not be identified
5. If P waves are seen, they are usually of an abnormal morphology (non-sinus) and the P-R interval will differ from a normal sinus complex

Question 2

3 origin of supraventricular premature complexes

Answer 2

1. atria
2. bundle of His
3. AV node

Question 3

T/F: It’s possible to differentiate SVPCs from ventricular premature beat from auscultation.

Answer 3

False.

Question 4

Definition of SVT

Answer 4

A run of four or more VPCs, the rate in excess of 200/min, but typically 250-350/min. SVT needs to be distinguished from a sinus tachycardia, which often exceeds 200/min and can reach in excess of 250/min (in dogs).

Question 5

ECG characteristics of SVT

Answer 5

The morphology is of a sequence of SVPCs and typically at a rate of >250/min

Question 6

Difference between supraventricular premature complexes versus junctional escapes?

Answer 6

Supraventricular ectopic complexes that occur before the next normal complex would have been due are termed supraventricular premature complexes (SVPCs), and those that occur following a pause such as a period of sinus arrest or incomplete heart block are termed junctional escapes.

Question 7

How to differentiate between supraventricular and ventricular arrhythmias

Answer 7

SVT: normal narrow QRS complex, rate 250-500/min, absence of fusion beats
Ventricular: wide and bizzare QRS complex, 180-300/min, presence of fusion beats

Question 8

What is the most common cause of atrial fibrillation

Answer 8

Atrial dilation, more usually in larger breed dogs.

Question 9

ECG characteristics of A-fib

Answer 9

1. Normal QRS morphology
2. R-R interval is irregular and chaotic (easier to hear on auscultation)
3. QRS complexes often vary in amplitude
4. No consistent and recognizable P waves preceding the QRS complex.

Supraventricular QRS morphology + chaotic R-R interval + absence of P wave = A-fib

Question 10

Clinical findings of A-fib

Answer 10

chaotic heart rhythm, quite fast, pulse rate is often half of the heart rate, 50% pulse deficit.

Question 11

Where does junctional escape rhythms originate from?

Answer 11

AV node or the bundle of His

Question 12

What is ECG characteristic of junctional escape rhythm?

Answer 12

1. fairly normal in shape
2. nodal escape rhythm is very slow, 50-70/min in dogs
3. usually in associated with bradyarrhythmias