=sinus nd dysfx w a 'defect in elaboration or conduction of sinus impulses w chaotic atrial activity, changing P wave morph, brady, interspersed ectopic beats/atrial tachy'
-incr risk w atrial switch for dTGA, repaired APVR, ASD repair, Fontan
-congen SA nd xx are not ommon
-SA nd malfrmn is assoc w LA isomerism
-may occur w congen hrt block
-familial clustering seen in some pts w/o CHD
-Extrinsic causes- autnomic imbalance, Rx
-heavily conditioned athletes get bradycardia and sinus pauses >2sec bc prominent vagal stim
-sleep apnea has an association
-antriarrhyth Rx can impair SA nd fx
ECG
-varied findings
-exercise testing good to check chronotropic response, should be able to get to HR of 180bpm w exercise; SA nd dysfx pt may show an exaggerated HR slowing or pause w recovery pd
Sinus Bradycardia
-#1 Sx of SA nd xx
-sustained or paroxysmal
-escape breat fr atrium, AVN, or ventricles, but often lower escape rate than expected bc of xx w these too
-though healthy kids can have pds of sinus brady w atrial/jctl escape
-DDX fr 2nd/3rd AVB, atrial and junctional extrasystoles...,
-check for sinus pause
Extreme Sinus Arrhythmia
-Sinus Arrhyth is due to autonomic influence w resp cycle
-AbNl = >100% variation in PP intervals
-SA nd exit block may cause variation in the amt....
Tachycardia-Bradycardia
-recurrent prolonged pause or sustained bady, then paroxysmal tachy
-tachy causes exaggerated overdrive suppression of the automaticity which is already impaired --> worsening bradycardia
Sinoatrial Exit Block
-failure of SA nd impulse to propagate
-Mobitz I SA block- gradual shortening of PP interval, then a pause of <2x the resting cycle length
-Mobitz II SA block- sudden pause of 2x the resting cycle length
-Complete SA nd block- cannot DDx fr sinus nd arrest by ECG
Sinus Pauses & Sinus Arrest
-prolonged pauses often bc of SA nd exit block or sinus arrest
-pause <2sec is Nl in young kids/teens
-A non sinus rhythm at rate < expected for age = escape rhythm --> c/s an underlying sinus arrest
Sinus Node Reentrant Tachycardia
-not common
-abNl conduction w/in sinus nd or in immed perinodal tissue
-P waves look like Nl P waves, but assoc w paroxysmal incr and decr in rate
-cannot ddx fr focal atrial tachycardia in close proximity to the SA nd
Atrial Flutter/Fibrillation
-uncommon w SA nd dysfx; IART and atrial muscle reentry is more common
-...
ECG Features
-Prolonged SA Conduction Time
-...
-Prolonged Sinus Nd Recover Time
-...
Tx
-no great Tx data
-SSS does NOT mandate Tx
-if mild/mod usually ASx and little risk of sudden death if ASx
-if acute Sx brady--> atropine, isproterenol, transQ pacing
-Rx no good for ch brady Tx
-Sx brady is a class I indication for pacing, ASx w HR <40 or pause >3sec is a class IIa in kids, Class IIb in teens
-...
-if pt also has a tachycardia, it complicates dual chamber pacing bc rapid atrial rate that is tracked could --> high ventric rate --> HD xx..., so need upper rate limit to avoid causing tachycardia...
...
Px
-progressive, w deterioration fo SA nd fx through adulthood
-sudden death fr bradycardia or prolonged sinus pause is rare
-if pt gets AV nd dysfx, its progression is slow...