AVNRT

AV nodal reentrant tachycardia (AVNRT), or atrioventricular nodal reentrant tachycardia, is a type of tachycardia (fast rhythm) of the heart. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycardia is the most common regular supraventricular tachycardia. It is more common in women than men (approximately 75% of cases occur in females). The main symptom is palpitations. Treatment may be with specific physical maneuvers, medication, or, rarely, synchronized cardioversion. Frequent attacks may require radiofrequency ablation, in which the abnormally conducting tissue in the heart is destroyed.

AVNRT occurs when a reentry circuit forms within or just next to the atrioventricular node. The circuit usually involves two anatomical pathways: the fast pathway and the slow pathway, which are both in the right atrium. The slow pathway (which is usually targeted for ablation) is located inferior and slightly posterior to the AV node, often following the anterior margin of the coronary sinus. The fast pathway is usually located just superior and posterior to the AV node. These pathways are formed from tissue that behaves very much like the AV node, and some authors regard them as part of the AV node.

The fast and slow pathways should not be confused with the accessory pathways that give rise to Wolff-Parkinson-White syndrome (WPW syndrome) or atrioventricular reciprocating tachycardia (AVRT). In AVNRT, the fast and slow pathways are located within the right atrium close to or within the AV node and exhibit electrophysiologic properties similar to AV nodal tissue. Accessory pathways that give rise to WPW syndrome and AVRT are located in the atrioventricular valvular rings. They provide a direct connection between the atria and ventricles, and have electrophysiologic properties similar to ventricular myocardium.

1. AVNRT

2. INTRODUCTION
 most common of the PSVTs, accounting for
nearly two-thirds of cases.
synonyms
AV junctional reentrant tachycardia.
Reciprocal or reciprocating AV nodal reentrant
tachycardia.
Junctional reciprocating tachycardia.

3. no apparent precipitating cause .
 However, in some patients, nicotine, alcohol,
stimulants, exercise, or surges in vagal tone
can initiate episodes.
Familial AVNRT has been reported

4. SYMPTOMS
•Palpitations
•Dizziness
•Dyspnea
•Chest pain
•Fatigue
•Syncope
•polyuria

5. Pathophysiology

11. AVNRT
•Presence of a narrow complex tachycardia with regular R-R
intervals and no visible p waves.
•P waves are retrograde and are inverted in leads II,III,AVF.
•P waves are buried in the QRS complexes –simultaneous
activation of atria and ventricles – most common presentation
of AVNRT –66%.
•If not synchronous –pseudo s wave in inferior leads ,pseudo r’
wave in lead V1---30% cases .
•P wave may be farther away from QRS complex distorting the
ST segment ---AVNRT ,mostly AVRT.

20. Atrioventricular node reentrant
tachycardia (the Jaeggi algorithm),
•pseudo S/R waves,
• the RP interval,
• the lack of significant ST depression in
multiple leads

a correct diagnosis of typical AVNRT can be
made by ECG analysis 76% of the time

27. ST segment depression
•represent either repolarization changes or a
retrograde atrial activation
•more commonly seen in those with an AV
reentrant tachycardia associated with an
accessory pathway

30. •aVL notch: any positive deflection at the end
of the QRS during tachycardia and its absence
during sinus rhythm.

36. relevant ECG parameters.
•ST-segment elevation in aVR lead.
– According to the definition, the percentage
of patients with aVR ST-segment elevation
was significantly greater in AVRT than in
AVNRT

39. •Although AV dissociation is usually not seen, it
can occur because neither the atria or the
ventricles are necessary for the reentry circuit

41. Clinical course
more likely to begin in young adults.
EP characteristics of the AV node can evolve over
time
The refractory periods of both the fast and slow
pathways increased.
The incidence of retrograde conduction through
the AV node decreased.
The cycle length of induced AVNRT increased

42. ELECTROPHYSIOLOGIC FEATURES
 Dual AV nodal physiology
may be distinct anatomic structures, or may
be functionally separate
fast or beta pathway : conducts rapidly and
has a relatively long refractory period.
slow or alpha pathway : conducts relatively
slowly and has a shorter refractory period.

43. Dual atrioventricular nodal
conduction
•Denes et al. in 1973,
• Antegrade dual pathways are demonstrable
in
75% of patients.
•Conversely, antegrade dual pathways can be
demonstrated without tachycardia

44. •optical mapping studies: multiple nondiscrete
atrial inputs to transitional zone surrounding
the AV node that is asymmetric- allowing an
excitable gap
•Unidirectional block occurring in the
transitional zone can transform the
nondiscrete pathways model into a classic
dual pathways physiology for AVNRT

45. Schematic representation of koch's
triangle and environment

46. •Schematic representation of
Koch's triangle which is bounded
by the tricuspid ring and the
tendon of Todoro. The tendon of
Todoro and the tricuspid ring are
in close proximity forming the
apex of the triangle near the His
bundle at the membranous
septum. Koch's triangle can be
divided into thirds: the anterior
contains the compact AV node;
the posterior contains the
coronary sinus; and the middle or
mid-septal third is between the
anterior and posterior portions.
The anterior third is associated
with fast pathways, and the
middle and posterior thirds with
slow pathways.

48. Electrophysiologic study in a dual AV nodal pathways
•The tracing shows three surface
ECG leads (I, II, V1) and
intracardiac recordings from the
high right atrium (HRA), bundle of
His (HIS), right ventricular apex
(RVA), and coronary sinus (CS).
During atrial pacing (S1) at a cycle
length of 600 ms (100 beats per
minute); the AH interval is 120
ms. An atrial premature beat (S2)
is added at a coupling cyle of 420
ms; this results in a prolongation
of the PR interval and increase in
the AH interval to 184 ms.

50. AVNRT Slow/Slow
•Characteristics
•Dual AV Nodal Physiology and jump with initiation
•Retrograde VA > 60 ms
•AH > HA
•Earliest Atrial Activation in posterior septal region
•Diferentiation of AVNRT Slow/Slow from AVRT with AVRT using a Concealed
Bypass Tract
•P wave morphology
–Negative in the Inferior Leads in both
•Delta RP (V1-II) > 25 ms
•Delta RP (V1-III) > 23 ms
•Delta RP (V1 - aVF) > 30ms

51. posterior or type B AVNRT - 2% of patients
with slowfast AVNRT; VA times are prolonged,
but the AH/HA ratio remains >1.
 Thus, it appears posterior slow-fast AVNRT
may actually represent the slow-slow form

52. MANAGEMENT

55. In patients with documented SVT (which is
morphologically consistent with AVNRT) but in
whom only dual AV-nodal physiology (but not
tachycardia) is demonstrated during
electrophysiological study.

56. Slow-pathway ablation may be considered at
the discretion of the physician when sustained
(more than 30 seconds) AVNRT is induced
incidentally during an ablation procedure
directed at a different clinical tachycardia

57. Posterior approach
•Koch's triangle can be divided
into thirds: the anterior contains
the compact AV node; the
posterior contains the coronary
sinus; and the middle or mid-
septal third is between the
anterior and posterior portions.
The anterior third is associated
with fast pathways, and the
middle and posterior thirds with
slow pathways. The anterior and
posterior approaches to ablate
the fast and slow pathways,
respectively, are indicated by the
position of the catheters (shown
in green).

58. • furthest from the His bundle - the lowest risk
of AV block.
• preserves fast pathway function- normal PR
interval after the ablation.
•Reliable anatomic and electrophysiologic
landmarks facilitate selection of a safe and
effective ablation site.

59. •A good ablation site records a small
fractionated or multicomponent atrial
potential, generally less than 10 percent of
the ventricular electrogram amplitude
•occurrence of transient junctional rhythm -
efficacy .

60. Identification of site for ablation
of AV nodal reentrant tachycardia
•Application of radiofrequency
(RF) energy to the tip of the HBE
catheter (HBE1-2) promptly
causes an accelerated junctional
rhythm (*), further evidence of a
good ablation site. Note that
during the accelerated junctional
rhythm, there is rapid 1:1
retrograde conduction to the
atria (A), evidence that the fast
AV nodal pathway is intact.
Following this energy application,
there was no evidence of slow
pathway conduction and no
inducible AVNRT.

61. •If the slow pathway is damaged but not
completely abolished, it may be possible to
induce single atrial echoes even though the
sustained arrhythmia has been eliminated

63. Anterior approach
In rare patients, AVNRT may occur in patients
who, during normal sinus rhythm, have a
markedly prolonged PR interval and absent
antegrade fast pathway conduction.
 who have previously had unsuccessful slow
pathway ablation

64. Anatomic variants
•exceptionally large coronary sinus ostium
distorts the usual fluoroscopic anatomy
• horizontal orientation
either with multiple fluoroscopic views or
electroanatomic mapping,

65. Atypical forms of AVNRT
•earliest retrograde atrial activation in fast-
slow - posteroseptal right atrium outside the
coronary sinus ostium.
• slow-slow form of AVNRT - within the
proximal coronary sinus, particularly the
superior portion

66. complications
Atrioventricular block
posterior displacement of the fast pathway
superior displacement of the slow pathway
(and coronary sinus)
 or inadvertent anterior displacement of the
catheter during RF application

67. Risk factors for AV block
Age
 fast junctional tachycardia (cycle length <350
ms) during the ablation
 Baseline PR prolongation
 relatively long refractory period in the fast
pathway

68. •Palpitations - 20 to 30 percent ; generally
transient - due to premature atrial or
ventricular contractions.
•inappropriate sinus tachycardia : disruption of
the parasympathetic and/or sympathetic
inputs into the sinus and AV nodes .

69. •RADIOFREQUENCY ABLATION VERSUS
CRYOABLATION
•(CYRANO) study, 509 patients were
randomized late recurrence of AVNRT was
significantly more frequent in the cryoablation
group (9.4 versus 4.4 percent)