Gen Med: Lecture 6- ECG Interpretation Flashcards
What is the normal pacemaker of the heart?
SA Node
What rate does the SA node fire at?
60-100 bpm
What do the internodal pathways and bachman bundle do?
Speed conduction to AV node and L atrium
What does the AV node do?
Slows conduction velocity to allow for atrial kick
What is the AV node seen as on the EKG?
PR interval, isoelectric line
What is the process of ventricular conduction?
Depolarization spreads rapidly beginning at IV septum
Stimulates muscle contraction from apex to base
What are the three properties of cardiac muscle?
Automaticity
Rhythmicity
Conductivity
What is the general name of the structures that can serve as the pacemaker if the SA node fails?
Automaticity foci or Ectopic Foci
What structures can be ectopic foci if the SA node fails?
Sites in atria, AV node, and ventricles
What rate do atrial ectopic foci fire at?
60-80 bpm
What rate do AV node ectopic foci fire at?
40-60 bpm
What rate do ventricular ectopic foci fire at?
30-40 bpm
What determines what pacemaker activity is used?
Faster peacemaking activity suppresses slower pacemaking activity
What happens to the interior of the cell during depolarization?
Positively charged
What creates the waves on EKGs?
Skin electrodes detect electrical potential differences
When depolarization wave moves towards positive electrode, wave shows up on EKG
What is a 12 lead EKG used for?
Diagnosis and medical management
What planes do the leads in a 12 lead EKG record in?
6 leads in frontal plane
6 leads in transverse plane
What can a 12 lead EKG be used to determine?
HR
Rhythm
Ischemia/infarction
Hypertrophy
What is a 1-3 lead EKG used for?
Exercise training
Acute care
What can a 1-3 lead EKG be used to determine?
HR
Rhythm
How many seconds are in one small square on an EKG?
.04 seconds
How many seconds are in one large square on an EKG?
.2 seconds
How is the voltage measured on an EKG?
.1 mV/mm
.1 mV/little square
What is the normal duration for a PR interval?
.12-.2 seconds
3-5 little boxes
What is the normal duration for a QRS complex?
.06-.1 seconds
1-3 little boxes
What is a regularly irregular RR interval?
Repeated patterns of irregularity
What is an irregularly irregular RR interval?
Completely chaotic
