EXAM #1: BASIC ECG Flashcards
Where does the Bundle of His lie?
Left side of the IV septum
What is the first part of ventricular depolarization?
High left ventricular septum
Is the sinus node depolarization contained in the PR interval?
No
Why is the T-wave upright?
Myocardium repolarizes in the opposite direction of depolarization
What is the clinical importance of the relative refractory period and the supranormal period?
Arrhythmiogenesis
Draw and label the hexaxial diagram.
p. 21
What does a small square on the ECG correspond to? What is one big square on the ECG?
- 04 sec
0. 20 sec
List the numbers that correspond to each large square in interpreting heart rate.
300 150 100 75 60 50 43 37 35 30
Vertically, what does one small square correspond to?
0.1 mV
Vertically, what does 1 mV equal?
2x large boxes
How do you check the regularity of the heart rhythm?
Check the R-R interval
What does the p-wave correspond to?
Atrial depolarization
Where should you look at the p-wave?
II and V1
In what leads are p-wave upright?
Inferior (II, III, and aVF)
Lateral (I and aVL)
Where will the p-wave normally be negative?
aVR
What is the normal p-wave duration?
Less than 0.12 sec or 120 msec
What is the normal p-wave amplitude?
Less than 0.25 mV or 2.5mm (small boxes)
What are the indications of a RAA? Where do you look?
II and V1= Tall/ narrow (greater than 2.5mm)
What are the indications of a LAA? Where do you look?
II= notched and greater than 0.12 sec V1= wide and biphasic
What does the PR interval correspond to?
Depolarization in:
- AVN
- His Bundle
- Bundle branches
- Purkinje fibers
What is the normal PR interval?
0.12-0.20 sec
What is the definition of a 1st degree AV block?
PR interval greater than 0.20sec
*Note that there are NO pathologic implications regarding a 1st degree AV block
What is a short PR interval?
PR interval less than 0.12
What does a short PR interval correspond to?
Pre-excitation
What is the normal QRS interval?
0.07 sec to 0.11sec
What does a wide ORS interval correspond to?
Bundle branch block
What is “low voltage?”
QRS complex is less than 5mm in amplitude in I, II, and III
What does low voltage indicate?
Current is not getting to the surface ECG
- Obesity
- Pericardal effusion
Where are Q-waves normal?
aVR II III aVF aVL V4-V6
What is the normal duration of a Q-wave?
Less than 0.03 sec (less than 1 small box)
What is the criteria for a pathologic Q-wave?
- More than 25% of the r-wave amplitude
- Wider than 0.03 sec
Where is the R-wave coming from?
Upper left IV septum
What is the normal R-wave progression?
Small r-wave in V1 and then getting bigger laterally
What is the normal S-wave progression?
Big s-wave in V1 and then getting smaller laterally
Where is the normal R/S transition?
V3 or V4
Transition between S-predomination to R-predomination
What does the ST segment correspond to?
Phase 2 or plateau phase
What is the normal amplitude of T-waves?
Limb= less than 5mm Chest= less then 10mm
What is concordance of the T-wave?
T-wave should have same deflection as QRS i.e.
- QRS +, T-wave +
- QRS -, T-wave -
What are very tall peaked t-waves an indication of?
1) Very early signs of MI
2) Hyperkalemia?
What is a U-wave?
Small rounded wave after the T-wave
What causes U-waves?
1) Hypokalemia
2) Quinidine
What is the QT interval?
Measurement of the duration of the entire cardiac cycle i.e. depolarization to repolarization
Remember that you measure from the beginning of the Q-wave to the end of the T-wave
How does the QT interval change with increased HR?
QT Interval gets SHORTER
What is associated with prolonged QT interval?
Sudden cardiac death
What is the normal QRS axis in the frontal plane?
- 15 to 100+
* Typically ~60+
How can you calculate the specific QRS axis in the frontal plane?
1) Find equipotential QRS complex
2) Go 90 degrees to that (positive)
