-10% of peds arrhythmias are 'disorders of impulse formation' (AET, MAT, JET...)
-unlike reentry tachys, these are fr a specific point in origin...
Automatic Atrial Tachy = Atrial Ectopic Tachycardia
Sx
-usually in kids w/o CHD
-can be longstanding in infant/toddler
-older kids p/w palpns, few w tachy related CM
-HR is slower than w reentrant SVT --> HR 120-160bpm
-paroxysmal w fast on/off like reentry or chronic form w slower on/offest. Ch form usually <150bpm but can --> CM
-not common in CHD pts, if + then likely in postop pd
Dx
-P before every QRS
-but if faster HR, harder to tell bc P might be buried in QRS
-ectopic P wave looks diff than baseline
-Holter--> gradual acceleration of HR w a 'warm up' pd
-the first beat of the tachycardia occurs late in the cardiac cycle (far from the last QRS, w a long RP) and the P wave looks similar to subsequent P waves (but diff than the previous, sinus, P wave)
-may see varying degrees of AV block d/o parasymp tone; this demonstrates it's not reentry bc that needs AV nd...
-might induce a block w adenosine, or transiently suppressed (so adenosine isnt a great test...)
-EP Study
-canot be stopped w overdrive pacing, unlike a-flutter
-w AV Nd Wenckebach (spontaneous or adenosine induced), you can exclude ventricular involvement
-now that you have ruled out PVCs/VT, the only other thing left in DDx of a rhythm w P before each QRS is a-flutter/IART--> cannot OD pace, but rather will only momentarily suppress the ectopic focus, then see it re-warm up and --> tachy again.
Tx
-Rx
-FAIL: Digoxin, propranolol, verapmil DO NOT WORK
-Class III - amio & sotalol, & Class IC (propafenone & flecainide) work better per small studies
-b-blocker + flecainide or amio + flec may help if refractory
-RF Ablation- 95-100% successful acutely
-most peds foci are in LA, near PVn or appendage, while in adults mostly RA side near RAA or SVC-RA jctn or CS os
-Spontaneous resolution occurs ___ frequently
-Thus, can Tx w Rx first and wait to see if later self resolves..., but if HD xx or Sx or poor response p 1-2yrs Rx, then c/s ablation
Junctional Tachycardias
JET- Junctional Ectopic Tachycardia
-fr w/in AV Nd or His Bundle
-most common is postop JET
-also see JET in infancy/toddler = congenital JET
-also see childhood/adolescent JET - accelerated jctl tachycardia
Post-JET
-NHx- usually transient
-decreasing incidence due to no longer doing atrial switches for dTGA; seen mostly w Norwood/Glenn/Fontan pts
-likely bc of fluid/electrolyte shifts, trauma, stretch, ischema @ AVN/His
-Rate150-240bpm; may --> decr CO, bc A & V contract at same time, so A contracts against closed AV vlv; poor ventric filling..., may --> decr BP thus incr endog catechols/incr inotropic support to maint Q to body; vasoconstriction--> cool to touch but elevated core temp bc of endog/exog catechols--> exacerbates the tachy.
==> MUST interrupt the spiral cycle of tachy+vasoconstriction+decr CO
-usually self limited but can --> xx
-slow the HR within 48hrs; if <170bpm usually better tolerated so less Tx needed
-can atrial pace to just above the jctl rate to ensure AV synchrony
-usually resolves by 5-7 days postop
-Dx
-c/s it if narrow tachy w P waves not seen or dissoc fr QRS, or if retrograde P wave w short RP, and RA pressure tracing showing cannon A waves
-may see AV dissociation if retrograde conduction is blocked
-check atrial electrogram to confirm Dx- see a rate is < jctl/v rate, + dissoc or VA relationship...
-Tx
-if 170-190 Tx, if >190 Tx urgently
-ensure fluid/volume ok; minimize inotropes, get to normothermia, get pain controlled, and c/s atrial overdrive pacing- 10 bpm higher than the jctl rate for AV sync
-c/s mild systemic hypOthermia to 35C; below 32C you may get ventric dysfx and risk of arrhyth
-c/s amiodarone (first line Rx), procainamide (digoxin no longer used)
-w amio, look for hypOtension w blus, w "gasping syndrome" ...
-c/s ECMO if else fails... (rarely needed now that we have amio)
Congenital JET
-Epi
-rare, but may be life threatening- 35% mortality in multicenter report
-usually <6mo
-p/w CHF often, may p/w compensated then rapid decline w tachy; 2 of the 9 deaths looked well ctrld
-Histology
-saw fibrous changes, divided, left sided, inflmn, focal degradation at AVN
--> ?die from tachy CM vs sudden complete heart block
-familial pattern in 1/2 of pts
-Dx
-narrow tachy +/-AV dissoc, P waves on 1 lead ECG are large & wide bc of anatomic EP AbNly of the atrium--> get atrial electrogram to confirm AV dissoc via tran-esoph or intra-atrial study
-HR usually <200bpm, may be as slow as 130-150bpm
-!!! but at slow rate, might have 1:1 VA conduction which confuses the Dx
-Adenosine challenge--> either block VA conduction or transient convert to sinus then resume the JET
-Tx
-amio =1st choice
-85% pts w high ds amio improved; 75% survival at avg 6yr f/u
-1/2 of pts were off Rx at 6yrs post, but there was still some slower JET
-ablation is definitive
-before amio, we would ablate the AVN & place a pacer; but now can use RF/cryo to ablate it w/o complete AV block
Accelerated Junctional Tachycardia
-Paroxysmal
-seen in otherwise well adults & older kid/teens w/o CHD
-bc of enhanced pacemaker current automaticity, usually @ AVN
-Non-paroxysmal = Accelerated Jctl Escape
-mainly in adults w acute MI, digox toxicity, COPD, rheuamtic carditis, hypErK, hypErCa, post CV surg
-fr triggered activity
-NHx
-usually slower, better tolerated than infant/child version
-sudden on/off, lasting seconds/hours OR gradual onset
-Rate 110-250bpm - wide range
-adrenergic stim- fever, stress, exertion...--> more sustained tachy and faster than the norm
-pts w the slower non-paroxysmal form might only get Sx w activity/stimulation when HR gets to 130-150
-usually benign
-Dx
-P wave dissoc fr QRS or not seen bc they are retrograde
-EP Study- His bundle before QRS, short VA time an dlong AV time; looks like an AVNRT
-might hve AV dissoc
-DDx AVNRT- pace at a cycle length shorter than that of the tachycardia (faster pace)--> AV interval shortens, eliminating block in a fast pathway, --> not possible for it to be conducting down the slow pathway, so not AVNRT (????)
-OD Pacing- variable response
-adenosine & burst pacing may --> transient stop JET
-Tx
-Tx if Sx enough/duration
-b-blockers first, then c/s flec or amio but if your at the amio/flec pt c/s RF/cryo ablation given risk of the Rx
Multifocal Atrial Tachycardia
-aka chaotic atrial rhythm
= P waves w at least 3 morphologies, w irregular P-P interval, w a rapid rate >100bpm
Sx
-nearly all adults w MAT have ch lung dz
-kids are a mix but most are very ill- 20-60% had resp illness of some sort, and resolution of the arrhyth doesnt necessarily parallel resp illness recovery, and O2 sat isnt assoc w degree of MAT either
-seen also w myocarditis, cyanotic heart dz, birth asphyxia
-1/3 of peds MAT is assoc w CHD (?)- varied types
-most peds cases however are incidental finding in an otherwise well infant w rapid, irreg rhythm
-may have h/o viral URI but often none
-if sustained/rapid may --> CM, 1/4 had dilation of heart cahmbers w abNl fx to some extent, but it normalized once arrhyth was controlled
-Most peds pts in their series (n=15) were infants
Epi
-small proportion of arrhyth in peds hospitals
NHx
-self limted regardless of Tx
-1/2 of pts have no residual MAT 5mo after Dx; no recurrence at long term f/u
ECG
-very irreg, might be very rapid- w atrial rate up to 400bpm
-see scattered, aberrantly conducted beats/pauses, due to sinus nd suppression after a run of MAT beats, and bc of blocked conduction of PACs; may see periods of sinus alternating w MAT
Mech
-triggered activity fr several ectopic sites
-?clear mech proven
-may be bc of variable propagation thru atrium of a single focus
-does NOT respond well to cardioversion or OD pacing, and the cycle length is irreg--> likely NOT re-entrant in nature
Tx
-poorly responsive to standard 1st line Rx, but must c/s if Tx really needed
-Correcting Mg, b-blocker (metoprolol), CCB (verapamil) - helps adults, this is NOT seen to work consistently in kids, but poor data on it.
-?propranolol response
-verapamil NOT USED IN INFANTS bc can --> HD colapse
-Amio seems to be Rx of choice for peds MAT if deemed one must be treated
-if ASx, no intercurrent illness, no CHD, no cardiac dysfx, then can just follow as outpt w/o more Tx/investigation. Check f/u ECG, Holter to ensure it isnt returning sporadically... until pt no longer has any MAT
-if +dysfx then c/s amio. Px d/o fx response once rhythm is normalized