Ecg Study

10. How many large boxes in one second?

* 1 large box equals 0.20 secs

11. How many small boxes in one minute?

* 1500 small boxes in 1 minute

12. How many large boxes in one minute?

* 300 large boxes in 1 minute

13. Define each of the following (what occurs during each?):

a) P wave = atrial depolarization (contraction), atriums contract , should come before QRS

b) PR interval = represents the time it takes the electrical impulse to travel from SA node to the AV node, lasts between 0.12-0.20 seconds

c) QRS complex = ventricular depolarization (contraction), atrial repolarization occurs, QRS is larger than P wave, greater than 0.12 seconds

d) QT interval = 0.36-0.44 sec ( 9-11) small boxes

e) T wave = ventricular repolarization (recovery of myocardial muscle)

f) Possible U wave = not normally seen on ECG, sign of potassium abnormality

14. What is the importance of the isoelectric line?

* Baseline for measuring the waves. Straight, flat line that connects all the curves, waves, and complexes. All waves and complexes are measured from this line.

15. Which waveforms do you expect to have positive (upward) deflections from the isoelectric line?

* P wave, R wave, U wave if it is visible on the ECG strip

16. Which waveforms do you expect to have negative (downward) deflections from the isoelectric line?

* Q waves, S wave

17. Define the 5 steps used for dsyrhythimia interpretation (be able to use this on rhythm strip)

* Step 1: Look at R-R interval

* Is the spacing the same between each R-R interval ( no greater than 2 small box difference)

* Count the number ofsmall boxes between R-R intervals

* Step 2: Calculating Heart Rate

* If HR is irregular, use 6 second strip (30 large boxes) and cound QRS complexes . multiply this number by 10 to get HR.

* If HR is regular, use 6 second strip (30 large boxes) and count small boxes between R waves and divide 1500 by that number to get HR...