EXAM2/CH18- Cardiac Electrical Pathophysiology Flashcards
____ % of the individuals who require pacemakers are over the age of 65 years
85%
85% of the individuals who require pacemakers are over the age of ____
65 years
____ pacemakers are implanted in the US each year
200,000
why is the number of pacemakers implanted growing?
because of the number of elderly people in the population
what 2 major factors increase need for a pacemaker
-CVD
-age
normal electrical conduction of the heart
SA node initiates the signal ->
signal passes through atria, stimulating contraction ->
AV node delays signal ->
bundle of His ferries the signal thru fibrous skeleton to interventricular septum ->
R+ L branches convey signal to apex ->
purkinje fibers carry signal thru ventricles, stimulating contraction from the bottom upward
what is the natural pacemaker where the heartbeat + depolarization is initiated
SA node
why does the AV delay occur
so that the ventricles cal fill
what does the apex do
separates R from L sides of the heart
sick sinus syndrome (SSS)
rhythm disorder involving the SA node
-individual has faulty SA node
-inability to generate a heartbeat or increase HR in response to the body’s changing circulation demands (if the SA node can’t generate a heartbeat, nothing else can happen)
sick sinus syndrome results in what 3 things
-bradycardia
-long pauses between heartbeats
-irregular heartbeats
symptoms of sick sinus syndrome
-heart palpitations
-angina
-fatigue
-light-headedness
-exercise intolerance
-syncope
syncope
brief loss of consciousness that occurs via fainting/passing out due to a sudden drop in blood flow to the brain
see slide 5 for SSS EKG
AV conduction block is also called
heart block
AV conduction block (heart block)
-loss of atrioventricular synchrony
-this is an issue with the AV node; SA node is working properly
-when the sa node is stimulated, it doesn’t pass the wave of stimulation to the AV node, so there is not an adequate contraction of the heart + the body does not get adequate bloodflow
AV conduction block or SSS is more life threatening
AV conduction block
symptoms of AV conduction block
similar to SSS
what is the body’s last ditch effort to generate a heart beat
junctional escape
-escape rhythms are not something you can survive off of past a few seconds/minutes
3 ultimate goals of pacemaker
-regular HR
-synchronize chambers of the heart (atrioventricular synchrony)
-defibrillate in case of arrhythmia
what 3 things make up the pacemaker (pulse generator)
-metal case (circuitry with battery)
-lithium batteries
-pacing leads (2 or 3)
where is the pacemaker implanted
just below the clavicle
-placed just below skin
-inferior to clavicle
how many pacing leads are in a pacemaker
2 or 3
pacemaker implantation
-fast, rather non-invasive
-can be done outpatient
describe the lithium batteries in a pacemaker
good because they last a long time (10+ years)
-given the time an individual has a pacemaker, we may need to go in to replace the battery
how does the pacemaker work
leads send sensory info to activity sensor that tells the pacemaker when to work
-where the leads get connected depends on what we are trying to fix with the pacemaker
3 types of pacemakers
-temporary external pacemakers
-permanent pacemakers
-AICD
temporary external pacemakers
-emergency
-ICU
-until permanent pacemaker placement
permanent pacemakers
the type of pacemaker we typically think of
AICD pacemakers
defibrillator
physiological pacing
sequence and timing of contractions between atria and ventricles to overcome CHRONOTROPIC INCOMPETENCE
-fixed rate vs. rate-responsive
chronotropic incompetence
when we don’t have the ability to generate a heartbeat
-pacemaker restores chronotropic competence
old school pacemakers were fixed rate or rate-responsive
only fixed rate
fixed rate pacemaker
pacemaker is limited to either lowering or increasing HR but doesn’t do both, only one or the other
-cardiologist will put a cap on the HR either on the lower or higher end
rate-responsive pacemaker
pacemaker can either increase or decrease HR when needed
-can go either direction
AV timing interval
signals ventricle to contract
optimal AV delay
how fast ventricle contracts