Slide 1
EP STUDYREENTRYAVNRT
WEVE TALKED ABOUTEQUIPMENTRELEVANT ANATOMYCATHETERS and PLACEMENTBASIC INTERVALSTESTS OF SN FUNCTION
EXTRASTIMULUS TESTINGREFRACTORY PERIODSINCREMENTAL PACINGMINIMUM PROTOCOL FOR DIAGNOSTIC EPS
AND NOWTACHYARRHYTHMIA MECHREENTRY MECHSVTAVNRT
Tachyarrhythmias
Basic mechanisms of tachyarrhythmiasEnhanced impulse formationAbnormal conduction
Enhanced impulse formationAbnormal automaticity (Phase 4)Least affected by Extrastimulus testingOverdrive pacing either overdrive suppression orNo effect
Enhanced impulse formationTriggered activity (Phase 3)Least common mech of SVT eg. Digitalis induced Initiated by overdrive pacing without conduction delay or blockOverdrive pacing Acceleration
Abnormal conduction impulse propagationReentryPathway - Anatomic, Functional, Both
reentry
3 conditions for reentryAtleast 2 functional (or anatomic) distinct pathways Joining proximally and distallyForming a closed circuit of conduction
3 conditions for reentryUnidirectional block in 1 of the pathways
3 conditions for reentrySlow conduction down the unblocked pathway allowing the previously blocked pathway time to recover excitability
3 characteristics of reentryInitiated by timed extrastimulus more effectively than rapid pacingProgrammed stimulation can also terminate Tachy
3 characteristics of reentryNo direct relation of pacing cycle length to the tachy cycle length
3 characteristics of reentryExtrastimulus can reset or entrain the Tachy in presence of fusion
Reentry is the MC mech of SVTs
EP evaluation of svt
6 tenets
1Mode of initiationRelation ofBasic drive cycle lengthES coupling intervalOnset of tachyTachy cycle length
Differentiates triggered activity from reentry
2Atrial activation sequenceP-QRS relation
3Effect of BBB during TachySpontaneous or induced BBBOn cycle lengthV-A conduction time
4Requirement of atria, HB, Ventricle in initation and maintenance of tachyEffect of AV dissociation on tachy
5Effect of atrial or ventricular stimulation during tachy
Differentiates AT, AVNRT, CBTEXCITABLE GAP
6Effect of drugs or physiological maneuvers during Tachy
AVNRT
MC SVT >50% SVTs
Concept by Mines in 1913Moe demonstrated on rabbit AVN! Dual AVN pathways
Typical or Common AVNRT
Typical or Common AVNRT
AlphaBeta
Atypical or uncommon AVNRT
Evidence of dual AVN pathways2 PR or AH intervals during NSR or at similar paced cycle lengthDouble response to an APC or VPCAbility to preempt Atrial echo by VPC during Slow pathway conduction during SVT
Definition of Dual AVN pathway
Definition of JUMP
Definition of JUMP> 50 ms increment in A-H interval with a small (~10 ms) decrease in coupling interval of Atrial extrastimulus
Definition of JUMP> 50 ms increment in A-H interval with a small (~10 ms) decrease in coupling interval of Atrial extrastimulus
Usually 70-100 ms jumpMaybe upto 500ms or more!
Apart from the typical JUMP by AESOther markers of dual AVN pathways Jump during NSR/Drive pacingBeat to beat change of > 50 ms in AH during pacingPacing induced increase in AH > PCL!
Apart from the typical JUMP by AESOther markers of dual AVN pathways Jump during NSR/Drive pacingBeat to beat change of > 50 ms in AH during pacingPacing induced increase in AH > PCL!
Double response to an APC or VPC
Apart from the typical JUMP by AESOther markers of dual AVN pathways Jump during NSR/Drive pacingBeat to beat change of > 50 ms in AH during pacingPacing induced increase in AH > PCL!Double response to an APC or VPC
May even lead to 1:2 Nonreentrant Tachy!
AV nodal conduction delay (A-H) is of prime importance in AVNRT Not coupling interval of AES
CRITICAL AV DELAY or CRITICAL AH INTERVAL
AES from CS vs HRASite of stimulation can affect ability to induce Dual pathway conduction and AVNRT
Critical AV nodal delay (A-H)required to initiate reentry is shorter in CS stimulation vs HRA
AES from CS vs HRADual pathway conduction and AVNRT EASIER to induce from HRA
AES from CS vs HRADual pathway conduction and AVNRT EASIER to induce from HRA
ImplicationPace from CS if no induction from HRAPost RFA check induction from both HRA and CS
InductionIf single AES doesnt increase AH sufficientlyDouble APCAtrial pacingShorter drive cycle lengthIsoproterenol, AtropineCS stimulation
Induction85% Typical AVNRTDual pathway seen in response to single HRA AES
Induction85% Typical AVNRTDual pathway seen in response to single HRA AES
Using all above methods Dual Pathway seen in 95% patients
Induction5-10% show MULTIPLE pathwaysMultiple jumps of >50 ms with shorter coupling intervals
AVNRT of different rates
InductionUpto 25% Non-AVNRT population also Dual pathway seen by these protocols
But
Only JUMP seen
InductionUpto 25% Non-AVNRT population also Dual pathway seen by these protocols
But
Only JUMP seenNo EchoNo Reentry over fast pathwayNo AVNRT
InductionUpto 25% Non-AVNRT population also Dual pathway seen by these protocols
But
Only JUMP seenNo EchoNo Reentry over fast pathwayNo AVNRTTherefore,LIMITATION IS RETROGRADE CONDUCTION OVER FAST PATHWAY
Induction by VESVentricular stimulation inducing AVNRT10-40% Typical AVNRT patientsVentr PACING more effective than VESOnly 10% induction by single VESDue to H-P refractoriness
Induction by VESTypical AVNRT patients retrograde conduction over FP very good
Ventr PACING more effective than VESOnly 10% induction by single VESDue to H-P refractoriness
Induction by V Pacing MechanismRetrograde over fast, concealed over slowDual pathway not seen No critical VA delay BEFORE AVNRT VA increases only when AVNRT induced
Induction by V Pacing MechanismFP retrograde refractory period > Slow pathwayDual AV pathway seenAtypical AVNRT induced
DETERMINANTS OF INDUCTION OF AVNRT
DETERMINANTS OF INDUCTION OF AVNRTRapid retograde conduction in FPTypical AVNRT patients 1:1 VA conduction at
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