EKG Flashcards
What is the P wave?
depolarization of the atria (first deflection on EKG)
What is the QRS?
depolarization of the ventricular muscles (therefore also repolarization of atria); Q: typically downward before upward reflection; R: upward deflection; S: downward
What is the T wave?
Repolarizaiton of the ventricles
How does conduction travel?
sinus beat starts in the SA node; depolarization spreads through the atria and reaches the AV node; epolarization continues to the bundle of His and bundle branches, Purkinje fibers, and ventricular myocardium; activation in the ventricles starts out on the left side of the IV septum and travels to the R
How many electrodes are used in EKG and where are they placed?
right arm, left arm, right leg (not used - grounds), left leg, V1-V6
Where are V1-V6 placed?
V1: 4th ICS, 2 cm to the right of sternum; V2: 4th ICS, 2cm to the left of sternum; V3 Midway between V2 and V4; V4 5th ICS, left midclavicular line; V5 5th ICS, left anterior axillary line; V6 5th ICS, left midaxillary line;
What are the direction of the different leads?
I: right arm to left arm; II: right arm to left leg; III: left arm to left leg; aVF: middle of body to left leg (down); aVL: middle of body to left arm; aVR: middle of body to right arm
In which directions should the EKG go?
If going towards a +, then up! If going away from a +, then down; if going towards a + and then past or away, then going up then down
What are the 8 most important things to look at in an EKG?
- Calibration;
- Heart Rate;
- Heart Rhythm;
- Intervals (PR, QRS,QT);
- Mean QRS Axis;
- Abnormalities of the P-wave;
- Abnormalities of the QRS (hypertrophy, bundle branch block, infarction);
- Abnormalities of the ST-segment/T-wave
What is important about calibration?
Standard calibration has a reference pulse of 1 mV (10 mm high) and a large box that represents 0.2 sec (200 ms)
How can you calculate heart rate from an EKG?
- 1,500/(# mm between beats) = HR;
- Count-off the # of large boxes between two QRS complexes: 300 – 150 – 100 – 75 – 60 – 50;
3.(Especially) for irregular rhythms such as atrial fibrillation:
Count the # of complexes during 6 sec of the recording and x by 10. ECGs often have time markers spaced 3 sec apart. If 3-second markers are not present, count out 15 big boxes: 15 boxes x 200 msec/box=3000 msec
What are the characteristics required for sinus heart rhythm?
1) Every P wave is followed by a QRS, &
2) Every QRS is preceded by a P wave, &
3) P-wave is upright in leads I, II, and III, &
4) The PR interval is greater than 0.12 sec (3 small boxes)
What is sinus bradycardia?
HR below 60 bpm
What is sinus tachycardia?
HR above 100 bpm
What is the corrected QT?
divide the measured QT/ square root of the R-R interval (in seconds); this is b/c QT interval should decrease as HR goes up
What is a normal PR?
120-200 msec (3-5 small boxes)
What does increased PR mean?
First-degree AV block
What does decreased PR mean?
Preexcitation/WPW, Junctional rhythm
What is normal QRS?
less than 100 msec (less than or equal to 2.5 small boxes)
What does increased QRS mean?
Bundle branch block, Ventricular ectopy, Drug effect (e.g., certain antiarrhythmic drugs), increased potassium
What is the normal range for QT corrected?
equal to or greater than 450m/460f msec
What does decreased QT corrected mean?
Short QT syndrome, elevated calcium
What does increased QT corrected mean?
decrease in K or Ca, Ischemia, Congenital, toxic drug effect (e.g., certain antiarrhythmic drugs); this is “long QT”
What is 1st degree AV block?
PR interval is more than 5 small boxes block slowing conduction down
