ECG Review Flashcards
Sinus tachycardia
Over 100 bpm
Sinus bradycardia
Under 60 bpm
Normal axis range
-30 -> +100
P-R interval definition
Atrial repolarization
End of P wave -> beginning of Q wave
QT and QTc interval definition
Represents the time from beginning ventricle depolarization -> ventricle repolarization.
Usually measured in the lead showing the longest QT and QRS intervals (not always lead 2)
Why does the P wave pause before it goes to the Q wave?
The pause after the P wave represents the slowing of depolarization through the AV node.
Allows time for the ventricle to fill with regurgitation “atrial kick”.
1st heart block is defined as what?
AV node conduction is greater than 0.2 sec (200 ms)
QRS interval definition and pathogenicity
Less than 0.12 sec (120 ms)
Longer = Left/right bundle branch blocks, left ventricular hypertrophy,
What does a prolonged QRS usually mean?
Bundle branch block which would impair right/left bundle conduction.
Prolonged = greater than 0.12 sec (120ms)
ST segments normal position and possible pathogenicity
Should be in line with the PR segment
Pathogenicity: Can be depressed or Elevated segments
- depressed = ischemia or poor blood flow
- elevated = dead tissue (this is worse)
QRS complex and its waves definitions
The time frame where the ventricles are stimulated and depolarized
Q wave specific definition = initial negative deflection immediately preceding the PR interval
R wave specific definition = the first positive deflection in the QRS complex
S wave specific definition = the first negative deflection preceding an R wave.
- Some ECGs may not show all 3 waves*
ST interval definition
Ending of ventricle depolarization -> end of ventricle repolarization
P wave definition
Atrial depolarization
T wave definition and pathogenicity
Ventricle repolarization
Usually 100ms- 250ms
- can be positive or negatively deflected, however the normal T wave will ALWAYS be ASYMMETRIC
Pathogenicity
- symmetric T waves = MI, hyperkalemia
J point definition and pathogenicity
Beginning of the ST segment (right immediately after the S wave of QRS
Prolonged J point (called J waves) = signs of systemic hypothermia
- note: this can be elevated, which signals early repolarization NOT MI OR ISCHEMIC TISSUE*
U wave
Final phase of ventricular repolarization right after the T wave
(may or may not be present is not considered pathogenic either way)
TP segment
End of the T wave -> beginning of P wave
Electrical resting state and is used to determine the phase line reference for PR and ST pathogenicity
RR intervals
Distance from the peak of the R wave on one QRS complex, subsequent QRS complexes R wave
*used as an alternative method to determine heart rate (60/RR (in seconds))
What should the calibration rectangle look like on an ECG to tell you if the ECG is properly calibrated?
Should be 2 full boxes tall (10 small boxes) and 1 full box wide (5 small boxes)
What is the conversion of mm -> mV in a standard calibrated ECG?
10 mm = 1 mV
Note 1 mm = 1 small box
PR interval duration definition and pathogenicity
Is the time it takes for the stimulus from the SA node to spread through the atria and into the AV junction
- is required so that the ventricles can fill properly with the preload form the atria
Normal time = 120ms- 200ms
Pathogenicity
- prolonged (>200ms) = 1st degree heart block
- shorted (<120ms) = WPW, atrial fibrillation, atrial flutter
Alterations to the QRS complex
QS wave =. One negative deflection preceding the PR interval
R wave = one positive deflection preceding the PR interval
QR wave = Large amplitude R wave w/ no negative deflection post R wave, but has one preceding the R wave.
Qr wave = small amplitude R wave w/ no negative deflection post R wave, but has one preceding the R wave.
rSR complex = one small amplitude Q wave positive reflection preceding a large negative reflection, w/ a large amplitude positive reflection after said large negative reflection
(reversed QRS complex)
R prime and S prime waves definition
When a QRS complex occasionally contains more than 2-3 deflections they are called prime waves
- R prime = positive deflections
- S prime = negative deflections
ST interval normal duration/position and pathogenicity
Normally isoelectric (w/ very slight elevation/depression being acceptable)
Normal time = 80ms
Pathogenicity
- depressed or elevated = MI and/or ischemic ventricular tissue
- elevation can also be left bundle branch block, left ventricular hypertrophy or acute pericarditis*
QT and QTc duration and pathogenicity
Normal = 300 ms- 450ms after correction (QTc = QT(ms)+ 1.75(HR-60))
Pathogenicity =
- prolonged = hypokalemia, hypocalcemia, low potassium, torsades, BB drugs, hypothermia, channelopathy
U wave duration and pathogenicity
There is no note worth time for normal U waves.
Normal U waves however should be no larger than the T wave and should have the same reflection
Pathogenicity:
- U wave > than T wave = hypokalemia
- opposite reflection of T wave = left ventricular hypertrophy or MI
