Electrocardiograms Flashcards
RNs will learn how to place and read EKGs.
Depolarization of the cardiac cell.
Na in and K out.
Ca++ in, which causes an action potential and muscle cell contraction.
Cardiac cells respond to an electrical impulse, causing movement of ions across the cell membrane resulting in contraction.
Shows up as QRS complex on the EKG.
Repolarization of the cardiac cell.
The cell changes back to a relaxed state.
Shows up as a T wave on the EKG.
Cardiac Pacemaker
Power supply of the heart that initiates and transmits an electrical impulse resulting in mechanical contraction (depolarization).
Sinoatrial Node
Normal (dominant) pacemaker of the heart.
Regulated by sympathetic and parasympathetic nervous systems.
Produces sinus rhythms at 60-100 bpm.
Atrioventricular Node
Backup pacemaker of the heart
Respons if normal SA node fails
Responsible for rhythms 40-60 bpm.
“Junctional rhythms”
Purkinje fibers
Final backup pacemaker of the heart.
Ventricular focus in the purkinje fibers.
Responsible for rhythms 20-40 bpm.
“Idioventricular rhythm”
Overdrive Suppression
The pacemaker with the highest rate suppresses all other pacemakers.
Helps heart pump as single unit.
No competition between nodes.
Describe the path of an electrical impulse through the heart.
SA node
Internodal pathways
AV node
Bundle of His
Left bundle
Right bundle
Purkinje fibers
Why is the P wave comparatively small?
The P wave represents electrical impulses being conducted through the atria in ring-like waves, which shows up as a small and rounded deflection on the EKG.
What centers are responsible for rapid ventricular depolarization?
The bundle branches and purkinje fibers carry the electrical impulses that cause the QRS complex.
What does the T wave represent?
The T wave shows ventricular relaxation.
What does the P wave represent?
Electrical depolarization (contraction) of the atria.
What does the QRS complex represent?
The QRS complex shows ventricular depolarization.
What is the PR interval?
The PR interval shows the length of time it takes for an electrical impulse to travel from the atria to the ventricles.
Remember, the AV node delays the impulse so that the atria and ventricles don’t all contract at the same time.
What is the vertical axis on an EKG a measure of?
An EKG measures voltage vertically in millimeters.
What is the horizontal axis on an EKG a measure of?
The EKG measures time horizontally in seconds.
One large square is 0.2 seconds, while each tiny square is 0.04 seconds.
What is voltage?
Voltage is the recorded amplitude of the electrical signal generated by the heart.
How does deflection work?
As depolarization moves across the myocardium, the electrical impulse is detected by the electrodes on the skin.
Electricity moving away from the electrode is negative deflection, and electricity moving towards the electrode is positive delfection.
What is normal paper speed for an EKG?
An EKG runs at 25 mm/second.
What is normal height calibration for an EKG?
Standard calibration is 10 mm in height.
How many electrodes are there for a 12 lead EKG?
Can you name them?
10 electrodes to produce 12 leads, which are:
Limb leads: Lead I, Lead II, Lead III, aVR, aVL, aVF.
6 chest leads.
Biphasic waveform
Electrical activity moves at right angles to an electrode.
What is the measurement for a normal P wave?
Does not exceed 2.5 mm in amplitude.
Less than 0.12 seconds long.
How long should the QRS be?
The QRS usually measures <0.12 seconds.
