Arrhythmias

Question 1

What is AVNRT?

Answer 1

-arrhythmias that represents 60% of arrhythmias presenting as SVT or PA and results from conduction through every entrance circuit comprising Fast and slow atrioventricular nodal pathways

Question 2

Which pathway in AVNRT has the longer refractory period

Answer 2

Fast pathway

Question 3

Which interval is prolonged in the beat that starts the reentry in ANRT?

Answer 3

PR interval

Question 4

Notes on AVNRT:

Answer 4

• The reentrant circuit is located within the AV node
• in most cases, both the atria and the ventricles are stimulated by impulses exiting from the circuit during each lap
• neither the atria nor the ventricles are necessary for the maintenance of the reentrant circuit
• it is possible to have block in the his bundle, preventing the ventricles from being stimulated, without affecting the reentrant circuit
• it is possible to have retrograde block, preventing the atria from being stimulated but without affecting the arrhythmia

Question 5

What is the typical heart rate during AVNRT?

Answer 5

150-250 bpm

Question 6

What are symptoms associated with Avnrt?

Answer 6

Neck pounding, palpitations, lightheadedness, near syncope

Question 7

Describe the location of the P-wave during AVNRT?

Answer 7

P-wave may be buried in the QRS complex or after the QRS complex, when will the P-wave is negative in the inferior leads and positive in lead V1, may manifest as small negative deflection in the inferior leads and small positive deflection in V1 (pseudo R prime pattern)

Question 8

Characterize the onset and termination of episodes in AVNRT

Answer 8

Abrupt onset and termination

Question 9

Is AVNRT more common in males or females?

Answer 9

Females

Question 10

What is the typical age of onset of AVNRT?

Answer 10

After the age of 20 years

Question 11

What methods can be used to terminate the AVNRT?

Answer 11

Blocking AV node conduction by changing autonomic tone or using pharmacologic agents

Question 12

Which pathway should be ablated during AVNRT?

Answer 12

Slow pathway

Ablation of the fast pathway significantly increases the risk of complete heart block.

Question 13

What anatomical site is typically used for ablation of the slow pathway?

Answer 13

Mid septal region between the contact AV node and the coronary sinus os to the posterior septal region around the os

Question 14

Which symptom associated with AVNRT is typical for the clinical presentation for this arrhythmia but not in other SVTs?

Answer 14

Rapid regular pounding in the neck

Question 15

What indicates a successful ablation for AVNRT?

Answer 15

1. High-grade (2nd or 3rd°) heart block
2. An increase in the refractories of the antegrade AV node
3. Elimination or alteration in dual AV nodal physiology

Question 16

Is the retrograde AV nodal conduction unchanged after slow pathway ablation?

Answer 16

Usually not

Question 17

List complications of fast pathway ablation

Answer 17

-High-grade (second or 3rd°) heart block
Marked 1st° heart block

• Pseudopacemaker syndrome caused by prolonged AV conduction times resulting in atrial contraction during AV valve closure
• Persistence of atypical AV nodal reentry employing slow pathway as both the anterograde and retro grade limbs of the tachycardia

Question 18

Describe the typical ECG presentation in AVNRT

Answer 18

Narrow, regular QRS complex tachycardia with no visible P-wave or P-wave located in the terminal portion of the QRS complex

Question 19

List helpful ECG patterns to differentiate if a tachycardia is AVNRT

Answer 19

R prime pattern in lead V1

Pseudo-S waves in inferior leads

No discernible P-wave separate from the QRS complex

Question 20

List three Diagnostic considerations for AVNRT in the EP lab

Answer 20

Typical AVNRT is rarely induced with ventricular pacing, this is the rule for atypical AVNRT

Administration of adenosine during the tachycardia helps differentiate and atrial tack from Etienne RT. If 80 block is produced while the atrial rhythm continues unchanged, this is highly suggestive of an atrial origin of the tachycardia.

Earliest activation at the low inter-atrial septum during tachycardia is consistent with AVNRT