SVT, AVNRT, AVRT, and pre excitation

Question 1

patient with WPW is most often

Answer 1

asymptomatic and seen on EKG for other reasons

Question 2

highest risk for arrhythmia pts are those who have

Answer 2

history of afib or AVRT (AV re entrant tachycardia) and with short refractory period (<250 msec of accessory pathway)

Question 3

to determine if these pts with WPW are at risk need to

Answer 3

risk stratify with non invasive tests (exercise testing or procainamide challenge or EPS)

Question 4

what does exercise testing show who are low risk for dangerous arrhythmias and have pre-excitation?

Answer 4

Will see intermittent loss of preexcitation (loss of delta waves on EKG) during faster heart rates with exercise or procainamide challenge – suggests a longer refractory period and will not conduct often enough during AF to degenerate into VF. These people are low risk and can be managed without further evaluation or treatment

Question 5

who gets EP (electrophysiologic testing) with catheter abalation procedure?

Answer 5

in symptomatic pts with cardiac arrhythmias (AVRT and pre excitation AF or flutter) and asymptomatic patients with high risk occupations (airline pilots and truck drivers and athletes)

Question 6

medications to avoid in pts who have preexcitation given their risk for degeneration from afib to VT

Answer 6

amiodarone or any AV nodal blocking agents (beta blockers, CCB, adenosine or digoxin) this results in blocking AV node and favorable conduction via the acessory pathway and can turn afib into VT in pts who have a WPW pattern on EKG.

Question 7

majority of pts with WPW on baseline EKG are:

Answer 7

asymptomatic

Don’t see a re entrant tachycardia in WPW but see normal sinus impulses reach ventricle first by an accessory pathway and shortly thereafter via the AV node. This can lead to the short PR interval, delta wave and widen QRS on EKG

But the WPW syndrome is when the pre existing WPW pattern on EKG develop symptomatic supraventricular arrythmias involving the accessory pathway and this causes palpitations, lightheadedness and pre syncope or syncope. Can have cardiac death in 1% of pts.

When in the WPW syndrome, there are _symptomatic supraventricular arrhythmias that form a reentrant circuit back to hear_t. causes widened QRS to convert to a narrow QRS tachyarrhythmia.

Question 8

symptomatic supraventricular arrhythmias happen because

Answer 8

the accessory pathway no longer pre-excites the ventricles and it instead forms a re entrant circuit back to the atria causes widened QRS complex to convert into a narrow QRS tachyarrhythmia and is seen as AVRT or reciprocating tachycardia. 80% of WPW pts.

Question 9

junctional escape beats

Answer 9

occur when sinus rate falls below the discharge rate of SA node. AV node becomes a dominant pacemaker.

Question 10

a fib can occur in 15-30% of pts with WPW syndrome by

Answer 10

accessory pathways with short refractory periods can preferentially transmit atrial impulses via the accessory pathway to ventricle to cause an irregular (supraventricular tachycardia with aberrancy or regular (ventricular tachycardia) wide QRS complex tachycardia.