Electrocardiography basics Flashcards
Purpose of ECG training
- recognize benign vs life threatening situations
- be able to make clinical decisions based on HR/rhythm as seen on a rhythm strip
what does the hearts ability to pump depend on
- automaticity:
- rhythmicity:
- excitability:
- conductivity
- contractility
- automaticity:
the ability to initiate it’s own electrical impulse
- rhythmicity:
the ability to repeat the cycle with regularity
- excitability:
the ability to respond to an electrical impulse
- conductivity
the ability to transmit electrical impulses from cell to cell within the heart (coordinates)
- contractility
the ability to stretch as a single unity and then passively recoil while actively contracting
Depolarization vs repolarization
- depolarization: depolarization is when the membrane potential becomes less negative (more positive)
- repolarization returns it to its resting negative state (more negative)
Sympathetic NS with the heart
- equated with acceleration
- branches of the sympathetic trunk
- discharges norepineprhrine resulting in increase velocity and force of contraciton
parasympathetic NS with the heart
- equated with deceleration or braking
- discharges acetycholine
- vagus nerve is main component and acts primarily on SA node as an inhibitor rate and velocity of impulse
Nodal myocytes
- within the SA/AV node
- susceptible to change and depolarization
transitional myocytes
- along the internodal pathways/bundle branches/purkinjie cells
- regular working myocytes
- myocytes have ability to fire automatically due to automaticity
SA node firing rate
- 60-100
- drives HR
AV node firing rate
- 40-60 and will take over if SA node is not firing properly
Myocytes firing rate
- <40
- can throw off rate
- etopci folki cells especially
ECGs - how many leads
1. diagnositc
2. bedside monitoring
3. holter monitoring
4. New technology
- diagnostic: 10-12 lead system
- bedside monitoring: 3-5 leads/rhythm strip
- holter monitoring: establish baseline/monitor change
- New technology: establish baseline/monitor change
what does a 12 lead ECG mean
- really only 10 leads
- 12 views of the heart that can tell where the irregularity is coming from
- diagnositic
bed side monitoring
- 3-5 leads
- used to monitor rate and rhythm
- may reflect issues that then require diagnostic EKG
- looks at ventricle
Holter monitor
- 24-48 hour EKG
- analyzed afterward
- electrodes attached at doctors
- wires attach to a small device
- record activities
New technology
- kardio mobile app
- zio mobile monitor system
- smart watch
- pick up the most common problems
ECG paper
- displays the time on horizontal axis
- runs at 25mm/sec
- at this speed each small box is 0.04 seconds
- each large box = 0.2 seconds
- 5 boxes = 1 sec
- 15 boxes = 3 seconds
- 30 boxes = 6 seconds
What do each part of the ECG mean
- P-wave: atrial depolarization n
- QRS: ventricular depolarization and contraction
- ST segment: beginning of ventricular repolarization to prepare for next beat
- T-wave: ventricular repolarization
Can QRS vary explain?
- yes
- can be different from individual to individual and from different views
5 rules when determining heart rhythm/dysrhythmias
- is the rhythm regular or irregular
- determine HR
- What atrial activity is evident
- what ventricular activity is present
- is there a relationship between Atrial and ventricular activity (p-wave with QRS complex)
- is the rhythm regular or irregular
(5 rules)
- are there pauses
- early beats
- are R-R intervals equal
CANNOT COUNT HR IF IT IS NOT EQUAL
- determine HR - what about HR?
- is it regular or irregular
- fast or slow
- What atrial activity is evident
- are P waves present, are they alike in appearance
- are there more Pwaves than QRS?
- what ventricular activity is present
- are QRS of normal duration (<.12seconds)
- are they uniform across the tracing
- is there a relationship between Atrial and ventricular activity
- is each P wave producing a QRS
- are there P waves without QRS
- is there QRS without a P wave
Calculating Heart rhythm (sinus rhythm)- what to use
- inspection
- calipers: see if they are the same distance
- marking paper to measure distance as well
Calculating HR
- IF rhythm is regular
- heart ruler
- # in 6 second intervals x 10
