pre-excitation

Question 1

wpw syndrome with sinus rhythm

Answer 1

ECG features of WPW in sinus rhythm are:

PR interval <120ms
Delta wave – slurring slow rise of initial portion of the QRS
QRS prolongation >110ms
ST Segment and T wave discordant changes – i.e. in the opposite direction to the major component of the QRS complex
Pseudo-infarction pattern can be seen in up to 70% of patients – due to negatively deflected delta waves in the inferior / anterior leads (“pseudo-Q waves”), or as a prominent R wave in V1-3 (mimicking posterior infarction).

Question 2

AVRT- ORTHODROMIC

Answer 2

• > Rate usually 200 – 300 bpm
• > P waves may be buried in QRS complex or retrograde
• > QRS Complex usually <120 ms unless pre-existing bundle branch block, or rate-related aberrant conduction
• > QRS Alternans – phasic variation in QRS amplitude associated with AVNRT and AVRT, distinguished from electrical alternans by a normal QRS amplitude
• > T wave inversion common
• > ST segment depression

AVRT is a form of paroxysmal supraventricular tachycardia.
A reentry circuit is formed by the normal conduction system and the accessory pathway resulting in circus movement.
During tachyarrythmias the features of pre-excitation are lost as the accessory pathway forms part of the reentry circuit.
AVRT often triggered by premature atrial or premature ventricular beats.
AVRT are further divided in to orthodromic or antidromic conduction based on direction of reentry conduction and ECG morphology.

Question 3

fbi…

Answer 3

fast broad irregular… when you have the sweet combo of atrial fibrillation and an acessory pathway that has a short refractory period.
I think you’re screwed.

Question 4

antidromic avrt

Answer 4

Rate usually 200 – 300 bpm.

Wide QRS complexes due to abnormal ventricular depolarisation via accessory pathway.

Question 5

Lown-Ganong-Levine syndrome

extremely rare, probably not important.

Answer 5

very short PR interval
normal P waves and QRS complexes
absent delta waves