= reentry circuit entirely within atria
Types of IART
-Atrial flutter- common in old ppl, espec if hrt dz, uncommon in infants/kids
-Atypical Atrial flutter
-Incisional IART
-more common in kids w CHD s/p palliation...
Typical Atrial Flutter
-93% of kids w a-flutter/IART have CHD
-a-flutter is <1% of peds arrhythmias
Mechanism
-requirements:
-corridor/isthmus bound by structural barriers (e.g. TV, CS, IVC, SVC, scar)
-fxl change in myocardium -->ing prolonged intra-aterial/inter-atrial conduction & increased atrial refractoriness
-eccentric premature depol away fr the Nl preferential atrial conduction pathway
-fxl barries (e.g. crista terminalis- has anisotropic properties) may also play a role to start/maint the a-flutter
ECG
-Typical = type I -->
-inverted sawtooth P waves in II, III, F (!!!)
= inferior to superior atrial activation
-Rate- 350-500bpm; in older kids/adults, usually 300bpm (range 240-350)
-w AV block--> pulse rate of 150bpm usually;
-a fixed rate of 120-150bpm ==> strongly c/s a-flutter w 2:1 AV block
-Atypical = type II -->
-positive sawtooth P waves in II, III, F (sup to inf direction)
-usually slower rate- around 200bpm
Tx
-observation-
-antiarrhythmic Rx
-atrial overdrive pacing
-DC cardioversion
-in young child, goal is to break it, instead of just to rate ctrl it.
-bc: usually wont recur if otherwise Nl heart, hard to slow the ventric rate w cardiac glycocides, b-blocker, or CCBs because the AV nd in kids is relatively rapid conduction; and bc ud rather avoid anti-coagulation in kids, and bc there is risk of a negative inotropic effect (espec if very young...), and bc overdrive pacing & DC cardioversion is successful usually
-newborn/infant
-often spontaneous conversion
-if persist >24 hrs or HD xx/Sx --> do cardioversion or OD Pacing
-a-flutter- usually composed of a single highly organized reentrant circuit --> minimal biphasic energy thru a patch at the anterior-posterior position is all that is needed - use 0.5-1 Joules/kg
-Transesoph atrial OD pacing- allows for rapid termination w electrical stim to atria and not the ventricles
-bc the rate might be to 400bpm, may need to go much higher
-pace to 20-25% faster than the flutter rate, until you have entrained (captured) the circuit,
-when both orthodromic & antidromic limb of the circuit are engagned by the pacing impulse, it causes the impulse/wavefront to collide and self extinguish within the circuit--> stop pacing and the sinus beat will take over
-repeat the steps till either the flutter is terminated or you lose capture
-will need a high pacing output- 10-15mA at 4-6msec pulse duration to capture the atria, well tolerated if for a brief period
-in older kids, if you want to rate control and then terminate initially, then c/s sotalol or amio (K ch blockers) 00> successful >60% of the time
-if older pt has a recurrence, and doesnt respond to Rx, then cs RF ablation (80% adult success rate)
Incisional IART
Epi
-in 1-25yo pts, common CHD is: TGA sp Mustard/Senning, Fontan, ASD, TOF, DCM, AVSD
-16% of Fontans get IART in their lifetime
ECG
-slower rate than typical a-flutter- <300bpm; usually 185-270 w Mustard, and 220-325 in Fontan
-P wave morph varies, usually small and fractionated; often need multiple lead ECG tracings to detect the P waves
-see fixed ventric rate of 100-150 or 2:1 block
-as atrial rate slows, the risk of 1:1 conduction increases --> faster ventric rates and incr in HD xx (!!!)
-Na Ch blockers can INCREASE risk by slowing the atrial rate, but bc of a vagally mediated reflex, causing an incr in AV nd conductance--> facilitate faster ventric rate (!)
Etiology
-in IART, the triangle of Koch is a high risk area, in TGA bc that's where a Mustard baffle lies; also high risk area is SVC-RA jct; in Fontan pts high risk area is bn atriotomy incision & crista terminalis, around AS patch, or bn IVC & TV
EP Study
... note that you may induce a rhythm that is not the same as the clinically relevant rhythm....
...
Tx
-Observation
-a-flutter in an otherwise well infant w/o CHD has a great Px and doesn't need long term Tx
-if IART, and well tolerated, self limited, then c/s observation after cardioversion, w close f/u and early MD notification if it recurs to prevent risk of thrombi formation; and tx w ASA ppx, though risk of thrombi is unknown.
-def attempt cardioversion within 24 hours of Sx onset to prevent thrombi formation
-if +thrombus by TEE, then first give warfarin x3 weeks before cardioversion if HD stable...
-Rx
-often need 2-3 Rx to ctrl it
-Rate ctrl + anti-platelt + anti-coagulation Tx needed if pt has had signif xx/HD xx
-b-blocker & CCB (diltiazam) are first line
-B-blockers- may suppress SA nd fx & ventric fx, so xx in some pts
-CCB- may --> negative inotropic effect, but usually no xx
-if frequent/poorly tolerated IART, then need rate and rhythm ctrl
-and start anticoag Tx for 3-6 months until you get good arrhythmia suppression
-Rhythm Tx: Na Ch blocker & K Ch blocker (at times together)
-Na Ch blocker xx- it slows myocardial conduction which is good, but may slow rate to the pt that you can slow a well tolerated 2:1 AV conduction to an untolerated 1:1 rate at a slow rate--> HD xx
-c/s guarding against this by starting a b-blocker or CCB when u start a Na Ch blocker
-K ch blocker- sotalol & amio- prolong myocard ERP also slow the AV conductance so less xx like Na Ch blocker...,
-but sotalol- more pro-arrhythmic than amio...
-RF Ablation
-75% successful, but 50% recurrence rate
-goal: create a line of block across the critical isthmus of the reentry circuit
...
-Pacing via an Atrial Anti-Tachycardia Pacemaker
-Tx atrial arrhythmia w overdrive pacing, and also can prevent arrhythm w stabalizing rhythms...
-blocks at least 50% of arrhythmias, espec w Mustard/Senning pts
-needs at least 2:1 AV conduction to kick in, ignores 1:1 conduction, so sometimes limited use...
Prevention
-surgical modifications being looked at...
Px
-a-flutter in infancy- great Px, most don't recur after the first one
-IART NHx is progressive..., much M&M, 5%mortality if well controlled, 20% if uncontrolled!
-ablation for IART effective- 75% short term, 50% long term benefit...