Indications
-Bradyarrhythmias
-Complete HB
-Sick Sinus Syndrome
-Rx induced brady
-tachyarrhythmia ctrl
-2nd/3rd AVB w Sx of low CO or intermittent low CO (syncope/presync) or ch exercise intol
-incr hrt size by CXR or echo, decr ventric fx, long QT, or wide QRS tachy intermixed w narrow QRS rhythm would all--> rec device placement
-must place pacer if pt has surgically induced complete HB >10 days; pt should not be discharged postop w/o 100% intact av conduction; later recovery p 10 days is unlikely; must have 24hr AV conduction on holter to say pt is ok w/o pacer
-if late onset complete HB, even if ASx, rec pacer; usually the HB is intermittent, but risk of sudden syncope is high, so rec pacing
-pts w sinus nd dysfx, usually h/o cv surg- if document jctl escape + Sx of low CO--> pacer bc the Sx will worsen over time; less so in young pt postop, but more so in teens/young adults
-Fontan pts at high risk for SA nd dysfx and for atrial arrhyth....
-Tachyarrhythmias
-some need Rx that --> resting brady--> need a pacer
-these pts often better off w pacer for anti-tachycardia Tx
-HOCM w signif LVOT gradient do better w dual chamber pacing; controversial- rarely used in practice
-Anti-tachy device indications- not precise for kids
-Ones capable of delivering antitathy pacing and defib shocks
-use if h/o near sudden death, or presyncope w documented VT --> needs ICD
-c/s ICD if high risk for ventric xx & much PVCs- TOF, CM
-Ones capable of delivering antitachy pacing only
-atrial flutter- keep atrial base rate above a baseline (70-80bpm) --> decr risk of flutter (?); couple it w anti-tachy pacing--> much better a-flutter ctrl
-dual chamber rate responsive pacemakers --> more used for atrial tachys in kids w SA nd dysfx in pts not amenable to ablation
-Heart Failure
-Cardiac resynchronization- thought that IVCD bn RV & LV--> differences in activation of the ventricles--> decr ventric fx. So pace both in a coupled manner--> more in sync--> better fx
-?effectiveness; works for some pts & not others
Device Choices
-Epi or Endocardial
-endocard- pt needs access; ?if ok in Fontan...,
-size- usually needs to be >20-30kg for endocardial
-Bipolar or Unipolar leads
-Unipolar = uses can...
-Bipolar- better, newer, higher impedance so less energy use, less interference fr far field R wave sensing, which interferes w atrial antitachy pacing, less extracardiac stimulation, less problems sensing
-Dual or Single Chamber?
Nomenclature:
-Paced, Sensed, Response to spontaneous beat, Presence of activity sensing, use of multisite pacing
ICD's
-dual vs single chamber ICD? -single chamber cannot ddx sinus tachy fr slow VT, & cannot Tx atrial tachys, so if a h/o atrial tachy in addition to VT then def need dual chamber
Cardiac Resynchronization Devices
-dual chamber pacer/ICD, track the atrial activity and enhance ventric filling by the AV delay to optimize CO
-limited access to the coronary sinus in small kids and those w funky anatomy
Implantation Technique
...
Device Interrogation
-battery impedance (rises as battery is depleted)
-battery voltage (less reliable/reproducible indicator of battery life)
-Electrode eval- ensure impedance hasn't jumped up recently- c/s fibrosis around the lead; c/s lead fracture if it decreases suddenly
-Electrode threshold testing - minimum voltage at 0.5msec pulse duration that --> 100% capture
-check for at least 2, pref 4 diff pulse amplitudes to estimate the strength duration curve
-If a lot of pts time is at higher HR--> c/s ng sensing programming
-Review pt Hx & asdjust programming...