Introduction to ECGs

Question 1

what is the fireing rate of the SA node?

Answer 1

60-100 beats per minute

Question 2

what is the conduction speed of the SA node?

Answer 2

2 meters/second

Question 3

what is the conduction speed of the AV node?

Answer 3

0.05 meters/ second

Question 4

what is the conduction speed of the bundle of his?

Answer 4

4 meters/ second

Question 5

what is the conduction speed of the contractile muscle cells?

Answer 5

1 meter/ second

Question 6

what is chronotropy?

Answer 6

the heart rate

Question 7

what is dromotropy?

Answer 7

the conduction speed

Question 8

what is Ionotropy?

Answer 8

the contractile strength

Question 9

Absolute refractory period (ARP)

Answer 9

no new action potentials can be initiated regardless of the stimulus stength.

Question 10

effective refractory period

Answer 10

includes the ARP plus a short segment of phase 3. a stimuli may cause cells to depolarize but not create an action potential

Question 11

releative refractory period

Answer 11

a greater than normal stimuli will depolarize cells and cause an action potential leading to abnormal beats or arrythmias

Question 12

supranormal period

Answer 12

a hyperexcitable period during which weaker than normal stimuli wil depolarize thee cells which could cause extra/premature beats

Question 13

how many seconds does a small 1mm box represent?

Answer 13

0.04 seconds

Question 14

how much seconds does a large box represent

Answer 14

0.2 seconds

Question 15

how many milivolts does a small box respresent?

Answer 15

0.1 millivolts

Question 16

what is the standard paper speed?

Answer 16

25mm per second aka 5 big boxs per second

Question 17

what is the normal time for the PR interval?

Answer 17

0.12-0.2 or 3-5 small boxes

Question 18

what does the PR interval represent?

Answer 18

the delay of conduction at the AV node

Question 19

why is there a delay of conduction at the AV node?

Answer 19

to allow for an atrial kick so 30% more blood canbe passed through to the ventricles

Question 20

how does the speed of the heart rate effect the PR interval?

Answer 20

a increased HR shortens the PR interval. a decrease in HR lengthens the PR interval

Question 21

what does the Q wave represent?

Answer 21

depolarization of the ventricular septum

Question 22

the depolarization of the ventricular septum moves in what direction

Answer 22

left to right, posterior to anterior

Question 23

what is the duration of a physiological or normal Q wave?

Answer 23

0.03 second

Question 24

what is the duration of a pathological Q wave?

Answer 24

longer than 0.03 seconds and has a 30% greater dip than R wave

Question 25

what does a pathological Q wave indicate?

Answer 25

a MI either from the past or ongoing

Question 26

what does the R wave represent?

Answer 26

ventricular depolarization and includes both the rise and decent on the ecg

Question 27

what does the s wave represent?

Answer 27

also depolarization of ventricles

Question 28

what is the normal duration of the QRS complex?

Answer 28

0.075 - 0.12 (less than 3 small boxes)

Question 29

what does a narrow QRS complex indicate? <0.12

Answer 29

- fast ventricular depolarization and that the electrical impulse followed the correct conduction pathway

Question 30

what does a wide QRS indicate? >0.12

Answer 30

slow ventricular depolarization and that the electrical impulses had issues with the conduction pathway

Question 31

gender difference of the QRS complex

Answer 31

can be 0.005 to 0.008 (milliseconds) faster in women than in men

Question 32

what does the ST segment represent?

Answer 32

early repolarization of the ventricles

Question 33

what does the uwave represent?

Answer 33

late repolarization of the ventricles/purkinjie

Question 34

what plane does the standard limb leads and augmented limb leads view the heart?

Answer 34

the verticle plane

Question 35

whate plane does the precordial leads view the heart?

Answer 35

horizontal plane

Question 36

when placing the leads the should be _____cm away from the heart to avoid distortion

Answer 36

10cm