ECG Basic Principles Flashcards
What is a electrocardiogram?
A graphic Representation of depolarization and repolarization in the myocardium
Where does the first depolarization take place?
Top left heart??? Not at the apex
Where does the Sinus node depolarization take place?
Right before the PR interval
Why are the repolarization and depolarization both positive?
They occur in opposite directions. and have opposite charges which cancel out.
How was the direction of cardiac impulses discovered?
Vector cardiography
What phase does the ST segment correspond to?
Phase 2
Where do the lines of einhoven’s triangle intersect?
the AV junction
What is different about the Transverse (V) leads?
There is no resistance in the leads
What are the methods of determining HR?
Count complexes in 6 sec or
Memorize the rates for each large square
What are the rates for each large square?
300 150 100 75 60 50 43 37 35 30
What are the Variables in ECG interpretation?
Duration
Amplitude
Morphology
Vector
What are the qualities of the P wave?
Record both atrial depolarizations
Upright in inferior and lateral leads
ALWAYS Negative in aVR
Duration
What are instances that would have a Positive P wave in aVR?
Incorrect lead placement
AV node is the pacemaker
What could prolong the P wave?
Larger atria making signal take longer to travel
Which lead is the best for looking at the P wave?
Lead 2
Anatomically, where is the Right/ Left atrium?
Anterior/Posterior
Where is V1 in relation to the RA?
It is placed directly over the RA
What will you see in a prolonged P wave in Lead 2?
A notch in the P wave
What can increse the P wave amplitude?
Larger mass of Atria
What does the PR interval tell you?
Depolarization events from atrium through AVN, his bundle, bundle branches, and purkinjie fibers
What is the normal duration of PR interval? 1st degree AV block?
.12-.20sec
PR >.20 sec
Increases with age
What is a short PR interval called?
Pre-excitation
What is the normal duration of QRS interval?
.07-.11 sec
What does increased amplitude of QRS tell you?
Decreased?
Tall or deep tells you increased muscle mass or chamber dilation
Low Voltage
What is the Q wave?
First downward deflection from baseline
When will a Q wave be visible?
After an MI there will not be the same cardiac activity to overshadow it.
Normal length of Q wave?
What is the R wave?
The first upward deflection from baseline
High left septum depolarizing toward V1
What happens to R wave as you go from V1-V6?
It increases in amplitude
What Is the Second R wave in the same complex called
R prime
What is the S wave?
First downward deflection from baseline after initil R wave
What happens to the Sa wave as you go from V1-V6?
It decreases in amplitude
What is the name of the point where the ST segment and the T wave come together?
The J point
What does an elevated or depressed J wave tell you?
Repolarization abnormality
What does the T wave tell you?
Ventricular Repolarization
What is the normal amplitude of T waves?
What direction does the T wave usually go?
In the same direction as QRS
What is a U wave?
Small, rounded wave after T.
What does the QT interval measure?
Measures duration of activation and repolarization or entire ventricular myocardium
Beg of QRS to end of T wave
What is the normal rane of axis in normal people?
-15 to 100 degrees
What is the Axis?
Mean direction of ventricular myocardiumdepolarization
What is the axis if 1 is positive and aVF is positive?
Normal
What is the axis if 1 is negative and aVF is negative?
Leftward
What is the axis if 1 is negative and aVF is positive?
rightward
