Abnormal PR segment and interval

Question 1

Describe the findings of Pericarditis.

Answer 1

Normal P wave
aVR: PR up and ST down
II: PR down and ST up
Electric Alterans.

Question 2

What is the pathogenesis of WPW

Answer 2

Bundle of kent that is early, but slow, depolarizes adjacent ventricles and creates a delta wave that forms part of QRS complex.
The AV conduction late but fast allows the QRS to bond with delta wave.

Question 3

Criteria of WPW.

Answer 3

Shorter PR interval
<120ms
slurred QRS complex (delta wave) >110ms
ST and T wave changes due to disproportional repolarisation.

Question 4

What causes a prolonged PR interval?

Answer 4

Heart blocks.
See heart block section