Chapter 5 preexcitation syndromes

Question 1

what are preexcitation syndromes?

Answer 1

there are accessory pahtways which current can bypass the AV node and thus arrive at the ventricles without the 0.1 seconds delay in the AV node, often ahead of time.

Question 2

what is WPW (wolff-parkinson-white) preexcitation syndrome

Answer 2

accessory conduction pathway acts as a short circuit allowing the atrial wave of depolarization to bypass the AV node and activate the ventricles prematurely.
It can be left or right sided depending on from which atrium to which ventricle is goes to.

Question 3

what appears in WPW (wolff-parkinson-white) on the ECG.

Answer 3

1. PR interval is shortened (less than 0.12seconds)
2. QRS complex is wider than 0.1 seconds by the presence of a delta wave. The delta wave shows up as a slurred.

The PR interval could also be outright missing or very short.

Question 4

supraventricular tachycardia in WPW, how does it work?

Answer 4

a premature atrial beat sends current down the normal conduction pathways but not through the refractory accessory pathway, Current that circles back through the accessory pathway which is no longer refractory to conduction forming a complete reentrant circuit.

RESULT: supraventricular tachycardia.

Question 5

how does the ECG look in a WPW?

Answer 5

• in WPW the reentrant loop reciprocates between the atria and ventricles the arrhythmia is more accurately termed: AV reciprocating tachycardia (AVRT).
• ANTEROGRADE ACTIVATION: (through AV node) narrow QRS = orthodromic tachycardia.
• RECIPROCATING tachycardias going in the opposite direction form a WIDE QRS = antidromic tachycardia

Question 6

what occurs when atrial fibrillation meets WPW?

Answer 6

ventricular fibrillation.