Premature atrial contraction

Question 1

What are the causes of ectopic foci in atrium?
What is the appearance of P wave?

Answer 1

• Hypoxia
• HypoK
• Catecholamines (increased epinephrine, norepinephrine)
• Stimulants (amphetamines, cocaine)
• Fires before SAN
• Looks different than SAN P wave

Question 2

Answer 2

Rate = 80bpm
Rhythm
R-R: irregular (some 2, some 4 small boxes between R-R)
P wave: yes, some abnormal
P –> QRS: AV association
QRS: narrow

Premature atrial contraction (decreased RR interval and irregular P wave shape compared to others)

Question 3

Answer 3

Rate = 120bpm (12x10 = 120
Rhythm
R-R: irregular
P wave: yes, but some abnormal (P and T wave fusion): can tell there is premature P wave due to decrease in R-R interval and early QRS complex
P –> QRS: AV association

There is PAC than normal compensatory pause then normal PQRS complex –> than PAC.
This is known atrial bigeminy

Question 4

Answer 4

Rate = 80bpm (8x10=80)
Rhythm:
R-R interval: irregular
P wave: present, but some abnormal
P –> QRS: AV association (even if SAN or ectopic foci is firing, it is going down through the correct conduction system)
QRS: narrow QRS complex

Definitely PAC when the RR is shortened (QRS comes before it should) and the P wave looks different

Every 2 normal PQRS complex there is a PAC. This is atrial trigeminy.