Narrow QRS Tachycardia
Tachycardias are broadly categorized based upon the width of the QRS complex on the electrocardiogram (ECG). A narrow QRS complex (<120 milliseconds) reflects rapid activation of the ventricles via the normal His-Purkinje system, which in turn suggests that the arrhythmia originates above or within the His bundle (ie, a supraventricular tachycardia). The site of origin may be in the sinus node, the atria, the atrioventricular (AV) node, the His bundle, or some combination of these sites. A widened QRS (≥120 milliseconds) occurs when ventricular activation is abnormally slow. The most common reason that a QRS is widened is because the arrhythmia originates below the His bundle in the bundle branches, Purkinje fibers, or ventricular myocardium (eg, ventricular tachycardia). Alternatively, a supraventricular arrhythmia can produce a widened QRS if there are either pre-existing or rate-related abnormalities within the His-Purkinje system (eg, supraventricular tachycardia with aberrancy), or if conduction occurs over an accessory pathway. Thus, wide QRS complex tachycardias may be either supraventricular or ventricular in origin.
Published on: Mar 3, 2016
Transcripts - Narrow QRS Tachycardia
NARROW QRS TACHYCARDIA
SVTs from a sinoatrial source:
Inappropriate sinus tachycardia (IST)
Sinoatrial nodal reentrant tachycardia (SNRT)
SVTs from an atrial source:
Ectopic (unifocal) atrial tachycardia (EAT)
Multifocal atrial tachycardia (MAT)
Atrial fibrillation with a rapid ventricular response
Atrial flutter with a rapid ventricular response
Without rapid ventricular response, fibrillation and flutter are usually not
classified as SVT
SVTs from an atrioventricular source (junctional tachycardia):
AVNRT or junctional reciprocating tachycardia (JRT)
Permanent (or persistent) junctional reciprocating tachycardia (PJRT), a
form of JRT which occurs predominantly in infants and children but can
occasionally occur in adults
AV reciprocating tachycardia (AVRT) - visible or concealed (including
Junctional ectopic tachycardia (JET)
Response to carotid sinus massage or adenosine –with
termination of arrhythmia with Pwave –AVNRT with atrial
premature beat .
Tachycardia persists with AV block –AT,AFL,SANRT
Pseudo r ‘ wave in V1 –AVNRT
SHORT RP interval – AVNRT,AVRT
Long RP interval – AT,SANRT,AVNRT atypical
Main Mechanisms and Typical Electrocardiographic Recordings of Supraventricular Tachycard
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
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.
AV NODAL REENTRANT TACHYCARDIA
Typical – RP interval < PR interval
RP interval > 80 milli sec
Atypical –RP interval > PR interval
Concealed bypass tract – only retrograde conduction
Manifest bypass tract– both anterograde and retrograde.
Electrical alternans –the amplitude of QRS complexes
varies by 5 mm alternatively.
Rate related BBB occuring and the rate of tachycardia
is decreasing –then the bypass tract is on the same side
of the block.
AV REENTRANT TACHYCARDIA
Antidromic is wide complex tachycardia
In NSR detected by delta wave.
Can ppt into AF and VF on use of AV nodal blockers
MEMBRANE ACTIVE ANTIARRHTYHMIC DRUGS are
CONCEALED WPW syndrome – no delta wave .less risk
Short PR interval
Normal QRS complex
Focal Atrial Tachycardia
P wave morphology changes.
PR interval > 0.12 sec .
Second,third degree AV block can occur.
Tachycardia terminates with a qrs complex ..
Right atrial origin– p wave inverted in V1.
If biphasic in V1—initially positive then negative.
Upright in lead AVL
Opposite if of left atrial origin
Superior origin –upright p waves in inferior leads
Inferior origin –p waves are inverted in inferior leads.
Focal atrial tachycardia (LA focus)
Multifocal Atrial Tachycardia
At least three consequtive p waves with different
morphologies with a rate > 100 bpm to be present.
Isoelectric baseline between p waves.
Also called as choatic atrial tachycardia
Mostly seen in COPD ,electrolyte abn,theophylline
Rate usually does not exceed 130-140 bpm.
Multifocal Atrial Tachycardia
Usually precipitated and terminated by premature atrial
Atrial rate is usually 120-150 bpm.
IART - Large or small reentrant circuit.
AV block can occur.
Non paroxysmal – accelerated junctional rhythm
Rate < 100 bpm Usually junctional node 40-60 bpm
Paroxysmal or focal junctional tachycardia is rare –
P waves may be before or after QRS complex
Infrequent and nonsustained episodes –no treatment
Acute termination of SVT and establish the mechanism of SVT
in case of acute setting.
Long term goal is abolishing the arryhthmia substrate.
Precipitating factors – electrolyte
imbalance,hypoxia,ischemia,hyperthyroidism to be sought
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