REENTRANT TACYCARDIA

1. NARROW QRS TACHYCARDIA PART II
REENTRANT TACHYCARDIA
DR.S.R. SRUTHI MEENAXSHI
MBBS MD PDF

3. ATRIAL TACHYCARDIA
• Atrial tachycardias have traditionally been characterized as automatic, triggered,
or reentrant.
• American College of Cardiology, American Heart Association, and Heart Rhythm
Society guidelines further defined sinus node reentrant tachycardia as "a specific
type of focal atrial tachycardia that is due to microreentry arising from the sinus
node complex, characterized by abrupt onset and termination, resulting in a P-wave
morphology that is indistinguishable from sinus rhythm"
• Atrial tachycardia is the overriding term that includes two major categories:
●Focal atrial tachycardia due to an automatic, triggered, or microreentrant mechanism
●Macroreentrant atrial tachycardia, including typical atrial flutter and other well-
characterized macroreentrant circuits in the right and left atrium
• Sinoatrial nodal reentrant tachycardia (SANRT), also called sinus node reentry or
sinus node reentrant tachycardia, falls into the latter group of reentrant arrhythmias

4. • Avnode anatomy
Koch triangle
boundaries are the
coronary sinus orifice,
tendon of Todaro, and
septal leaflet of the
tricuspid valve

5. • The anterior third, which contains the AV node and fast
pathways
• ●The middle third
• ●The posterior third, the usual site of slow pathways

6. • Dual AV nodal physiology — The simplest concept of
AV nodal physiology that allows for reentry involves
separate electrical pathways within or proximal to the AV
node
• One pathway conducts rapidly and has a relatively long
refractory period. This is called the fast pathway.
• The second pathway conducts relatively slowly and has a
shorter refractory period. This is called the slow pathway.

7. In typical AVNRT, the P wave is usually buried within or
fused with the QRS complex, resulting in a pseudo-R' (a
second R wave) in lead V1 and a pseudo-S wave in the
inferior leads.
In atypical AVNRT, the P wave occurs late after the QRS
complex, often appearing shortly before the next QRS
complex, resulting in a pattern that resembles atrial
tachycardia.

8. TYPICAL AVNRT
• Typical AVNRT — The common form is also called "typical AVNRT" or "slow-fast" AVNRT.
• Typical AVNRT usually initiates as follows
●A premature atrial complex arrives at the AV node when the fast pathway is in its refractory period. Thus,
antegrade conduction down the fast pathway is blocked.
●The premature beat conducts via the slow pathway, through the final common pathway, to the bundle of
His. As a result, the PR interval of the premature beat will be longer than those of normal beats conducted
through the fast pathway.
• ●If the fast pathway has recovered its excitability by the time the slow pathway impulse reaches the
distal junction of the two pathways, the impulse can conduct retrograde up the fast pathway. The circuit
may then become repetitive with antegrade conduction back down the slow pathway and retrograde
conduction up the fast pathway resulting in a sustained tachycardia (figure 3 and figure 4).
• This proposed mechanism explains a number of clinical observations in AVNRT:
• ●A single PAC (or retrograde penetration of the AV node from a junctional or premature ventricular
complex/contraction [PVC; also referred to a premature ventricular beats or premature ventricular
depolarizations]) can initiate the arrhythmia.
• ●Penetration of the reentrant circuit by a premature beat can abruptly terminate the arrhythmia.

11. Typical AVNRT
• ECG:P waves are often hidden – being embedded in the
QRS complexes.
• Pseudo r’ wave may be seen in V1
• Pseudo S waves may be seen in leads II, III or aVF.

14. Note rate greater than 100
narrow qrs tachycardia
pseudo r ‘ wave in v1
pseudo s wave in inferior leads
diagnosis- avnrt

16. ATYPICAL REENTRANT TACHYCARDIA
• Atypical AVNRT — Up to 20 percent of patients with AVNRT
have uncommon forms of the arrhythmia, referred to as
"atypical AVNRT." As examples:
 Antegrade conduction can occur down the fast pathway with
retrograde conduction up the slow pathway.This is referred
to as "fast-slow" AVNRT.
 Some patients have multiple slow pathways, resulting in
"slow-slow AVNRT" variants in which both the antegrade and
retrograde limbs of the circuit utilize slow AV nodal pathways.

17. Atypical AVNRT
Note RP interval prolonged
Retrograde p waves in inferior
leads
Shortening of PR interval

18. AVRT
• AV reentrant (or reciprocating) tachycardia (AVRT) is a reentrant tachycardia with an
anatomically defined circuit that consists of two distinct pathways, the normal AV
conduction system and an AV accessory pathway, linked by common proximal (the atria)
and distal (the ventricles) tissues.
• major types orthodromic and antidromic AVRT. The width of the QRS complex can usually
distinguish
1. Orthodromic AVRT – If the tachycardia has a narrow QRS complex, the antegrade limb is
the AV node/His-Purkinje system. In this setting, any preexcitation (manifest as a delta
wave on the surface ECG) seen during sinus rhythm is lost since antegrade conduction is
not occurring via the accessory pathway.)
2. Antidromic AVRT – If the tachycardia has a wide QRS complex, the possibilities include
AVRT with antegrade conduction over the accessory pathway (antidromic AVRT) or
orthodromic AVRT with aberrant QRS conduction resulting in a wide QRS complex

21. Orthodromic AVRT
• ECG findings in orthodromic AVRT — The ECG during
orthodromic AVRT and typically shows the following:
• ●Ventricular rate ranging from 150 to 250 (or greater) beats
per minute and usually regular
• ●Narrow QRS complexes (in the absence of underlying
conduction system disease or in the absence of aberrancy)
• ●Inverted P waves with an RP interval that is usually less than
one-half the tachycardia RR interval

22. Note short PR segment
slurring of qrs complex
Delta waves
conduction to accessory pathway WPW – kent pathway

26. Anti dromic avrt (wide qrs)

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