ECG - Tachycardia Diagnosis

Question 1

What can be assumed if the QRS complex is <0.12 s in terms of conduction pathway?

Answer 1

The depolarisation signal has passed through the bundle of his and into bundle branches and purkinje fibres, which are fast conducting systems

Question 2

What assumption can be made about the type of tachycardia if it is narrow complex?

Answer 2

It is most commonly an SVT

Question 3

What is the conducting rate of conducting tissue?

Answer 3

4-8 ms

Question 4

What is the conduction rate of the myocardium?

Answer 4

0.5 ms

Question 5

What are causes of broad complex tachycardia?

Answer 5

Distinguish primarily between

• VT - ventricular origin
• SVT with aberrancy - BBB or antegrade conduction via accessory pathways

Can also be caused by Electrolyte abnormality

Question 6

What are the most common phsyiological causes of tachycardias?

Answer 6

Re-entrant loops or enhanced automaticity of region of cardiac tissue

Question 7

What are the characteristics of a sinus tachycardia?

Answer 7

• Regular narrow complex tachycardia
• +ve P-wave axis in II, III and aVF, and V5 and V6
• PR interval 0.12-0.2 s

Question 8

What occurs to PR interval in junctional tachycardia?

Answer 8

Significantly shortened due to distance between depolarisation focus and AV node being shorter than distance between SA node and AV node. Depending on how close to the AV node the focus is, the P-wave will occur before, during or after the QRS (as displayed in image)

Question 9

What happens to the P-wave axis in junctional tachycardia?

Answer 9

P-wave axis inverts, representing superior depoolarisation of atria from AV node

Question 10

What are the characteristics of a junctional tachycardia?

Answer 10

• Regular, narrow complex tachycardia
• Abnormally short PR
• P-waves - pre/post QRS or absent

Question 11

How would you distinguish a junctional tachycardia from AF?

Answer 11

AF is irregular, and JT is regular

Question 12

What are characteristics of a focal atrial tachycardia?

Answer 12

• Regular, narrow complex tachycardia
• Change in p-wave axis - depending on focus site in atria
• Normal PR interval
• P-wave morphology constant

Question 13

What does a constant p-wave morphology per beat and normal PR interval with an altered p-wave axis indicate?

Answer 13

Focal atrial tachycardia

Question 14

What are characteristics of multifocal atrial tachycardia?

Answer 14

• Irregularly irregular tachycardia
• Change in p-qave axis per beat
• Normal PR interval

Question 15

What are underlying causes of an irregularly irregular rhythm?

Answer 15

• AF - most common
• Multifocal atrial tachycardia