Download Approach to narrow QRS tachycardia

Approach to narrow QRS
tachycardia
 The normal RMP in myocardium is -90 mv
 SA node differs from myocardium by

RMP is -65 mv

low overshoot

short duration
 The phase 1 repolarisation corresponds to isoelectric ST segment
of ECG
RELATIONSHIP OF INTRACELLULAR
POTENTIAL TO SURFACE EKG
RELATIONSHIP OF INTRACELLULAR
POTENTIAL TO SURFACE EKG
SN
P
VP
ARP
RRP
RELATIONSHIP OF INTRACELLULAR
POTENTIAL TO SURFACE EKG
Properties resposible for any arrythmia is
abnormal
automaticity
conductivity
refractoriness
Mechanism of Tachyarrhythmia
Abnormal impulse formation Abnormal impulse conduction
Automaticity
Enhanced
Abnormal
Triggered
Reentry
EADs DADs Anisotropy Anatomic
Fu
CLINICAL EVALUATION
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History
Palpitations - Greater than 96%
Dizziness - 75%
Shortness of breath - 47%
Syncope - 20%
Chest pain - 35%
Fatigue - 23%
Diaphoresis - 17%
Nausea - 13%
• CLINICAL CLUES FROM
• PULSE
• JVP
• HEART SOUNDS
• Diagnosis of arrythmias is made by
•
rate and regularity of P wave,P-P interval
•
relationship of P and QRS
•
configuration of P and QRS
If the P wave is not found modifications
LEWIS lead
RA to Rt 2nd ICS
LA to Rt 4th ICS
Esophageal lead
Intracardiac lead
LADDERGRAM OR LADDER DIAGRAM
• Depicting temporal relationship between
atrial and ventricular repolarisation
• Timing correlates with ecg in horizontal
direction
• A---- Pwave duration
• A-V ------P-R segment
• V------QRS duration
Approching ECG
Atrial flutter features
• Rapid ,regular atrial rhythm at a rate of 200-400/min
• Waves are regular ,uniform amplitude in morphology and amplitude .No
iso electric segment in between
• Usually 2:1 or 4:1 conduction to ventricle
• Wenkebach type conduction can occur
• 1:1 conductive response suggests
Accesery pathway
Class 1A,1C drugs slowing rate of AFL (Hence Class IA and IC
drugs should be administered in conjunction with an AV nodal blocking agent (beta
blocker or calcium channel blocker)
Catecholamine excess like exercise,excitement,induction of
Anesthesia
IV atropine
• Usually transient
• Associated with underlying structural heart
disease
• Digoxin convert AFL to AF
• Sodium blocking drugs convert AF to AFL then to
sinus rhythm
• Markedly enlarged atria tend to have slow rate
• Ectopic atrial tachycardia and AFL seldom coexist
in same pt
Mechanisms
• A large or small re entrant loop
• Single or multiple focus of automaticity
• “Isthmus of slow conduction”
It is in postero septal part of rt atrium betwn
orifices of IVC, coronary sinus ,tricuspid
annulus ring
– It is the promising target for ablation to interrupt
AFL :Ablation is commonly performed at the 6:00 position on the
tricuspid valve isthmus
Types of atrial flutter
Type 1 (common/typical)
rate 240 -350/mt
can be entraine d byatrial pacing
subdivided into
counterclock wise (cephalad)(Most common)
inverted in Lead 2,3, aVF
positive in V1
clockwise (cranial to caudal)
positive in Lead 2, 3, aVF
either positive or negative in V1
Type 2 (less common)
rate 340-430
cant be entrained by pacing
Type I Atrial Flutter
• Typical atrial flutter, or "isthmus-dependent" flutter,
is a macroreentrant arrhythmia that involves a long
slow path with an excitable gap, forming a circuit
within the right atrium.
• Slowly conducting reentrant circuit is located in the
low right atrial isthmus.
• The isthmus of tissue is between the inferior vena
cava and tricuspid annulus.
Type I
Type I
Type II Atrial Flutter
• Atypical atrial flutter lacks an excitable gap and is not
isthmus-dependent.
• Usually this rhythm results from an intra-atrial
reentrant circuit that is very short.
• May be due abnormal anatomy within the right or
left atrium (i.e. surgical scars, irregular pulmonary
veins, disturbed mitral annulus)
Diagnosis: EKG
• EKG will typically show 2:1 conduction across the AV
node (even ratios of conduction are more common
than odd ratios)
– May need to administer adenosine to slow conduction
through AV node
Typical Atrioventricular Nodal Reentry
tachycardia ( AVNRT)
Electrophysiology study
CLASSIFICATION OF AVNRTS
AH/HA
VA(Hs)
ERAA
Typical
AVNRT(slow –
fast)
˃1
˂60ms
RHs,CS os,LHs
Atypical
AVNRT(fastslow)
˂1
˃60ms
CS os,LRAS,dCS
Atypical AVNRT ˃1
(slow-slow)
˃60ms
CS os,dCS
VA indicates interval measured from the onset of ventricular activation on
surface ECG to the earliest deflection of the atrial activation in the His bundle
electrogram; ERAA, earliest retrograde atrial activation; RHis, His bundle
electrogram recorded from the right septum; LHis, His bundle electrogram
recorded from the left septum; LRAS, low right atrial septum; CS os, ostium of
the coronary sinus; and dCS, distal coronary sinus.
*Variable earliest retrograde atrial activation has been described for all types
of AVNRT