Dick - Atrial Ectopic, Atrial Automatic, Junctional, & Multifocal Tachycardia

AET & Junctional Tachycardia & MAT - Dick10&11

-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

-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

-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.

-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

-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

-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