Download Approach to narrow QRS tachycardias

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CardioMonday Oct.2005
Approach to narrow
QRS tachycardias
EL-SAYED M.FARAG
(Msc.Cardiology)
Definiton
Narrow QRS complex tachycardias(NCT) are defined as
tachyarrhythmias with a rate faster than 100 beats/minute
and a QRS duration of 120 msec (0.12 sec) or less, as
demonstrated on the electrocardiogram (ECG) or cardiac
monitor.
The normal QRS duration reflects normally synchronous
activation of both ventricles through the His bundle, bundle
branches, and terminal Purkinje conduction system.
SA
node
Beat Originates from SA ,atrial tissue or AV
Node
QRS Complex: normal, narrow
AV
node
Internodal
Pathways
Bundle
of His
Purkinje
Fibres
Bundle
Branches
The narrow QRS complex
tachycardias include:
 Sinus tachycardia (ST)
 Inappropriate sinus tachycardia (IST)
 Sinoatrial nodal reentrant tachycardia (SNRT)
 Atrial tachycardia (AT)
 Multifocal atrial tachycardia (MAT)
 Atrial fibrillation (AF)
 Atrial flutter (AFl)
 Junctional ectopic tachycardia (JET)
 Nonparoxysmal junctional tachycardia (NPJT)
 Atrioventricular nodal reentrant tachycardia (AVNRT)
 Atrioventricular reentrant tachycardia (AVRT)
Mechanisms
Altered automaticity
Triggered activity
Reentry
1. Altered Automaticity
Hypothermia decrease, hyperthermia increase phase 4
slope
Hypoxia & hypercapnia both increase phase 4 slope
Cardiac dilation increases phase 4 slope
Local areas of ischemia or necrosis increases
automaticity of neighboring cells
Hypokalemia increases phase 4 slope, increases
ectopics, prolongs repolarization
Hyperkalemia decreases phase 4 slope; slow conduction,
blocks
2. Triggered Activity
Afterdepolarization reaches threshold

Early: interrupt repolarization

Delayed: after completion of AP.
3. Reentry
Requires: available circuit, unidirectional
block, and different conduction speed in limbs
of circuit
Exp: WPW reciprocating tachycardia, AVnodal reentry, …..
The “Re-Entry” Mechanism of Ectopic Beats &
Rhythms.
Electrical Impulse
Cardiac
Conduction
Tissue
Fast Conduction Path
Slow Recovery
Slow Conduction Path
Fast Recovery
Tissues with these type of circuits may exist:
• in microscopic size in the SA node, AV node, or any type of heart tissue
• in a “macroscopic” structure such as an accessory pathway in WPW
The “Re-Entry” Mechanism of Ectopic Beats &
Rhythms.
Premature Beat Impulse
Cardiac
Repolarizing Tissue
Conduction
(long refractory period)
Tissue
Fast Conduction Path
Slow Recovery
Slow Conduction Path
Fast Recovery
1. An arrhythmia is triggered by a premature beat
2. The beat cannot gain entry into the fast conducting pathway
because of its long refractory period and therefore travels down
the slow conducting pathway only
The “Re-Entry” Mechanism of Ectopic Beats &
Rhythms.
Cardiac
Conduction
Tissue
Fast Conduction Path
Slow Recovery
Slow Conduction Path
Fast Recovery
3. The wave of excitation from the premature beat arrives
at the distal end of the fast conducting pathway, which has
now recovered and therefore travels retrogradely
(backwards) up the fast pathway
The “Re-Entry” Mechanism of Ectopic Beats &
Rhythms.
Cardiac
Conduction
Tissue
Fast Conduction Path
Slow Recovery
Slow Conduction Path
Fast Recovery
4. On arriving at the top of the fast pathway it finds the slow
pathway has recovered and therefore the wave of excitation ‘reenters’ the pathway and continues in a ‘circular’ movement.
This creates the re-entry circuit
NCT WORKUP
ECG
Lab. Workup ( CBC,TFT,s.electrolyte,
24 hour Holter monitor
Continuous loop event recorder
Echocardiogram
Treadmill test ( with or after exercise)
ALL ARE NARROW BUT THE
DIFFERENCE IS WIDE !!
Tachycardias Arising From the
Sinus Node Region
Sinus tachycardia and Inappropriate sinus
tachycardia
Sinus node rentry tachycardia
Sinus node reentry tachycardia
Sinus node reentry tachycardia arises from a reentrant circuit
involving the sinus node, producing P waves that are fairly similar
if not identical to those during sinus rhythm.
sinus node reentry can be initiated and terminated abruptly by a
premature atrial stimulus, which is consistent with its reentrant
mechanism. It is usually nonsustained and associated with slower
rates than inappropriate sinus tachycardia, making it clinically
insignificant.
Carotid sinus massage and other vagal maneuvers typically slow or
terminate sinus node reentry.
Inappropriate sinus tachycardia
It is a clinical syndrome characterized by sinus tachycardia without an
identifiable physiologic stimulus. Secondary causes for resting sinus
tachycardia must be ruled out, such as anemia, hyperthyroidism,
pheochromocytoma, and diabetes mellitus with autonomic dysfunction.
At least two clinical variants have been described: (1) resting heart rate of
100 beats/min or greater and (2) increased heart rate response to minimal
exertion .Sinus rates greater than 200 beats/min are not characteristic of
inappropriate sinus tachycardia, and paroxysmal increases in heart rate are
not seen.
The mechanism of inappropriate sinus tachycardia is still speculative but is
thought to be a primary abnormality of the sinus node complex
characterized by a high intrinsic heart rate, beta-adrenergic hypersensitivity,
and accentuation by a depressed cardiovagal reflex .
Atrioventricular
Node Reentrant Tachycardia
(AVNRT)
The most common form of paroxysmal SVT is AV node
reentrant tachycardia (AVNRT), which accounts for
greater than 60% of cases referred to an electrophysiology
laboratory. Patients typically present in their 30s or 40s,
with greater than 70% being women .Although the
mechanism for AVNRT is reentry involving the AV node,
the precise location of the reentrant circuit is uncertain but
includes atrial tissue surrounding the AV node. The
reentrant circuit consists of an anterograde limb and a
retrograde limb.
Types of AVNRT
Common (Slow – Fast).
Uncommon :
*Fast-Slow
*Slow-Slow
Common AVNRT
Uncommon AVNRT
Atrioventricular Reentrant Tachycardia
Mediated by Accessory Pathways .
The second most common form of paroxysmal SVT is AV
reentrant tachycardia (AVRT) using an accessory pathway
Accessory pathways are discrete bundles of myocardial tissue
bridging the atrium and ventricle along the tricuspid or mitral
valve annulus. More than half of accessory pathways are
situated in the left free wall, 20% to 30% occur in the
posteroseptal location, 10% to 20% occur in the right free wall,
and 5% to 10% occur in the anteroseptal location near the AV
node .
Because the accessory pathway conducts more rapidly
than the normal conduction system, the ventricle is
producing a short P-R interval and a delta wave on the
surface ECG.
In contrast, about 25% of accessory pathways conduct
only retrogradely and are not manifest on the ECG
during sinus rhythm (Concealed accessory pathway).
Orthodromic atrioventricular reentrant tachycardia
involving an accessory pathway,the tachycardia is narrow
complex because of anterograde conduction down the AV
node and His-Purkinje system. Retrograde atrial
activation over the accessory pathway results in a P wave
within the early ST segment .
Ex.RT.Anteroseptal AP
Atrial Tachycardia
Atrial tachycardia is less common than AVNRT or AVRT,
accounting for fewer than 15% of patients referred for
electrophysiology study. It can occur in the pediatric
population, especially in children with surgically corrected
congenital heart disease. Atrial tachycardia usually arises from
a single localized atrial focus .
Atrial Tachycardia (3:2 & 2:1)
Paroxysmal junctional reciprocating
Tachycardia ( PJRT)
Multifocal atrial tachycardia (MAT)
Multifocal atrial tachycardia is a rare SVT. It involves more than one
atrial focus and requires at least three distinct P wave morphologies to
be diagnosed on the surface ECG.
Because the foci fire independently of one another, the atrial rate is
irregular and typically averages 100 beats/min. The P-R interval also
may vary depending on the location of the foci relative to the AV node
The mechanism for multifocal atrial tachycardia has not been defined
clearly but may be due to enhanced automaticity or triggered activity.
Most patients with this arrhythmia have exacerbations of severe
underlying pulmonary disease with hypoxia.
MAT
Jnctional Tachycardia
Junctional tachycardias arise from a discrete focus within the AV
node or the His bundle. In the pediatric population, junctional
tachycardia also is known as junctional ectopic tachycardia.
Junctional ectopic tachycardia presenting before 6 months of age
usually is associated with underlying heart disease that carries a high
mortality. In contrast, adult junctional tachycardia has a more benign
prognosis and typically develops after the acute phase of myocardial
infarction, digitalis intoxication, and acute myocarditis.
Although the precise mechanism for junctional tachycardia has not
been defined, it is likely due to enhanced impulse initiation in the
region of the AV node by automaticity or triggered activity rather
than reentry
Nonparoxysmal atrioventricular
junctional tachycardia in a healthy
young adult .Top ,This tachycardia
occurs at a fairly regular interval (“Wshaped” complexes) and is interrupted
intermittently with sinus captures that
produce functional right and left bundle
branch blocks .Middle ,Two P waves
are indicated by arrowheads. The
junctional discharge rate is
approximately 120 beats/min (cycle
length = 500 milliseconds) and the
rhythm irregular, sometimes shortened
by sinus captures or delayed by
concealed conduction that resets and
displaces the junctional focus .
Bottom ,Carotid sinus massage slows
the junctional as well as the sinus
discharge rates.
Atrial Flutter
Atrial flutter is an atrial arrhythmia characterized by
a regular rate, a uniform morphology, and a rate
greater than 240 beats/min. Atrial flutter is usually
accompanied by a fixed 2:1 ventricular response,
and it is this rapid ventricular response that results in
most symptoms. Atrial flutter may be observed
transiently after cardiac surgery or may persist for
months to years. Many different forms of atrial
flutter exist, which has led to multiple classification
schemes.
Classification of atrial Flutter

Common (Typical)
- Isthmus dependant
- Non Isthmus dependant

Uncommon (Atypical)
Type I atrial flutter
Type II atrial Flutter
Atrial Fibrillation
Atrial fibrillation (AF) is the most common sustained
cardiac rhythm disturbance occuring in approximately 0.4
to 1% of general population with increasing prevelance
with age (10% over 80 years)
AF may be:
Primary, no underlying disease
Secondary to: HPT, IHD, MVD, …...
Increased Morbidity
Embolic complications (stroke)
Reduced cardiac function; hemodynamic changes
Complaints and symptoms
Increased mortality
Induction of atrial fibrillation
by a premature atrial beat
originating in the orifice of
one of the pulmonary veins.
These triggers can be
caused by microreentrant
circuits that occur in the
transitional zone of cells as
the pulmonary vein
endothelium transitions into
the left atrial endocardium
The trigger for the
induction of intermittent
atrial fibrillation is
located in the
pulmonary veins in 90%
of patients and outside
the pulmonary vein
area in 10% of patients
IT IS TOO WIDE
HOW TO NARROW??
Take home messege

Observe either the onest or the termination.

Note the P ,PR and RP.

Do vagal maneuver and adenosine.
STILL VAGUE?
EPS
Electrophysiologic study
HRA
HRA
HIS px
HIS
HIS ds
CS
Abl
CSp
RV
CSds
RVa
Ex. Concealed LLAP
Ex.SA reentry
Ex. PAF (RUPV)
EX.Atrial tachycardia by CARTO
(electroantomic mapping)
HOW TO TREAT?
Narrow-Complex Supraventricular
Tachycardia, Stable
Attempt therapeutic diagnosis maneuver
• Vagal stimulation
• Adenosine
Preserved
EF<40%, CHF
Junctional tachycardia
Preserved
Paroxysmal supraventricular
tachycardia
Ectopic or multifocal
atrial tachycardia
• No DC Cardioversion
• Amiodarone
• B-Blocker
• Ca2+ channel blocker
• No DC cardioversion
• Amiodarone
Priority order:
•Ca2+ Channel blocker
• B-Blocker
• Digoxin
• DC cardioversion
• Consider procainamide,
amiodarone, sotalol
EF<40%, CHF
Priority order:
• No DC cardioversion
• Amiodarone
• Diltiazem
Preserved
• No DC cardioversion
• Ca2+ channel blocker
• B-Blocker
• Amiodarone
EF<40%, CHF
• No DC cardioversion
• Amiodarone
• Diltiazem
Non Pharmacologic AF therapy
Catheter ablation.
Atrial pacing (single or dual site pacing).
Intraatrial ICD.
AFFIRM TRIAL
RACE TRIAL
SPECIAL GROUP NEEDS
SPECIAL TREATMENT
WHAT IS COLOUR OF THIS
TISSUE???!!
Thank You