Pacemakers and ICD's Flashcards
Indications of pacemaker
-SA node dysfunctions eg. symptomatic brady, sinus arrest
-acquired AV block- symptomatic mobitz 1+2 or 3rd degree
-post heart transplant
-hypertrophic cardiomyopathy
-long QT syndrome
-cardiac resynchronisation therapy for severe cardiac failure
How 2 different pacemakers work
-fixed rate- usually 67bpm resting rate
-on demand- pace only when required
How on demand pacemaker works
-has upper and lower limit to rate by calculating R-R interval
-if R-R too short pacemaker can inhibit pacing
-if R-R too long pacemaker can pace causing systole
3 Types pacemaker
-single chamber- just one ventricle or atria
-dual chamber- atria and ventricle
-biventricular- both ventricles
Pacemaker ECG features
-pacemaker spikes
-broad QRS complex- due to ventricular depolarisation occurring outside the conduction system
-appropriate discordance- we expect to see slight ST segment elevation or depression and T wave in opposite direction to QRS complex
Pacemaker spikes
Short spikes of less than 2ms
-atrial pacing will have a pacemaker spike before P wave
-atrial and ventricular pacing will have pacemaker spike before P wave and QRS complex
-ventricular pacing will have pacemaker spike before QRS
What can go wrong with pacemaker
-failure to fire- due to battery, lead fracture, break in lead insulation or poor lead connection
-failure to capture- pacemaker spike but not followed by atrial/ ventricular complex due to mechanical failure, MI, drugs, metabolic abnormalities
-over/ under sensing- pacer incorrectly senses or misses intrinsic depolarisation causing failure to pace or pacing when unnecessary
-pacemaker syndrome
What is a fusion beat
-when the ventricle is simultaneously activated by both the paced and supraventricular
(native) impulses.
-pacemaker spike is shortened and QRS duration narrowed as normal impulse is occurring at same time as pacemaker fires
Pacemaker syndrome
-when you lose atrioventricular synchrony
-atria contract at same time or after ventricular contractions decreasing cardiac output
-causes cardiogenic shock or HF
-pt require upgrade from single chamber to dual chamber
Pacemaker problems treatment
-CABCDE
-O2 if needed
-atropine if indicated
-DON’T give fluids if hypotensive unless reduced GCS as not problem with blood vol but problem with pump
-convey to ED
What is an ICD (implantable cardioverter defibrillators)
-monitor heart rhythm and if shockable rhythm detected, shock would be administered
Indications of ICD
-survivor of CA due to VT or VF
-spontaneous or sustained VT with syncope
-sustained VT with evidence of severe HF
-those at risk of VF/VT eg. HOCM, long QT syndrome, ARVC
S-ICD (subcutaneous ICD)
-newer device doesn’t require leads to be attached to heart
-less invasive so fewer risks
-generally used in younger and fitter pts
-result in fewer inappropriate shocks
Fitting of ICD
-inferior to collarbone, similar to pacemaker
-2 leads inserted, one superior aspect of R atria other in inferior aspect of R ventricle
-this allows electricity to flow across the length of the heart
What is a ring magnet and what does it do
-if ICD firing inappropriately place ring magnet over ICD
-this stops the shock function
How many shocks will an ICD give before shutting down
-if in VF or VT, ICD will give a max of 8 shocks
-if still in VF or VT after 8 shocks, it will shut down
-shocks generally under 40j
