Normal ECGs DSA

Question 1

What causes the heart to beat?

Answer 1

rhythmic discharge of electrical stimuli

Question 2

What is an EKG?

Answer 2

records the electrical activity of the heart, provides a record of cardiac electrical activity, & info about heart function/structure

Question 3

What does the EKG record?

Answer 3

electrical activity of contraction of heart muscle (myocardium)

Question 4

How does the depolarization move throughout the heart?

Answer 4

cell to cell conduction of depolarization is carried by fast-moving Na+ ions

Question 5

Where can you detect the heart’s electrical activity?

Answer 5

from the skin surface using electrodes

Question 6

What does an upward wave indicate on an EKG?

Answer 6

depolarization wave moving toward positive electrode

Question 7

What is the SA node?

Answer 7

in upper posterior wall of RA & is the heart’s dominant pacemaker

Question 8

What is automaticity?

Answer 8

ability of SA node to generate pacemaking stimuli

Question 9

What does the P wave represent?

Answer 9

contraction of BOTH atria

Question 10

What happens to depolarization when it reaches the AV node?

Answer 10

depolarization slows down to allow time for blood in atria to enter the ventricles (b/c carried by slow moving Ca2+ ions)

Question 11

What happens when depolarization reaches the ventricular conduction system?

Answer 11

depolarization rapidly shoots through the His bundle & the L/R bundles branches

(purkinje fibers)

Question 12

What are Purkinje fibers?

Answer 12

rapidly conducting cells that use fast moving Na+ ions for conduction of depolarization to ventricular myocytes

Question 13

What is the QRS complex on the EKG?

Answer 13

depolarization of the entire ventricular myocardium

Question 14

How does ventricular depolarization spread?

Answer 14

from terminal filaments of Purkinje fibers beneath endocardium that proceeds outward to epicardium of ventricles

Question 15

What does the ST segment represent?

Answer 15

ventricular repolarization

Question 16

What does an abnormal ST segment indicate?

Answer 16

sign of serious pathology (if elevated or depressed beyond normal baseline level)

Question 17

What is the T wave?

Answer 17

rapid phase of ventricular repolarization (K+ leaving the myocytes)

Question 18

What does ventricular systole include?

Answer 18

begins w/ QRS & persists until end of T wave

Question 19

What is a long QT interval syndrome?

Answer 19

pts vulnerable to dangerous rapid ventricular rhythms

Question 20

What ions are used in cell to cell conduction in myocardium?

Answer 20

by Na+ ions

Question 21

What ions are used in AV node conduction?

Answer 21

slow movement of Ca2+ ions

Question 22

Where would you place electrodes?

Answer 22

on R & L arms, L leg

Question 23

What are the lateral leads?

Answer 23

Leads I & AVL b/c each has a positive electrode positioned laterally on the L arm

Question 24

What are the inferior leads?

Answer 24

leads II, III & AVF b/c each of these leads has a positive electrode positioned inferiorly on the L foot

Question 25

What is at the center of leads V1 to V6?

Answer 25

AV node

Question 26

What are leads V3 & V4 over?

Answer 26

oriented over the interventricular septum (V3 near RV & V4 near LV)

Question 27

What are bipolar limb leads?

Answer 27

pair of electrodes on each limb that has 1 positive & 1 negative

Question 28

What direction is lead I in?

Answer 28

horizontal (L arm is + & R arm is -)

Question 29

What is + & - in lead III?

Answer 29

L arm is negative & L leg is positivve

Question 30

What is the AVF lead?

Answer 30

uses L foot electrode as positive & both arm electrodes as negative

Question 31

What is the AVR lead?

Answer 31

R arm is positive & others are negative

Question 32

What is the AVL lead?

Answer 32

L arm is positive & others are negative

Question 33

How is the rate of an EKG read?

Answer 33

cycles per minute

Question 34

What is the most common cause of sinus tachycardia?

Answer 34

sympathetic stimulation of SA node via exercise

Question 35

automaticity of atria

Answer 35

60 to 80 beats per minute

Question 36

automaticity of AV junction

Answer 36

40 to 60 beats per minuate

Question 37

automaticity of venticles

Answer 37

20 to 40 beats per minute

Question 38

What happens if AV junction is blocked?

Answer 38

automaticity focus in Purkinje fibers of ventricles will act

Question 39

What is the importance of overdrive suppression?

Answer 39

provides emergency backup pacing @ 3 separate levels

Question 40

What should you first use to calculate the rate?

Answer 40

R wave

Question 41

What are the next 3 thick lines following R wave?

Answer 41

300, 150, 100 | then 75, 60, 50

Question 42

How do you determine rate?

Answer 42

start with 1 R wave & where next R wave falls gives you the rate

Question 43

If rate is 60 beats per minute & due to rhythm from automaticity focus, which one is producing the rate?

Answer 43

pacemaker in the AV junction would also not see any P waves on that ECG

Question 44

What is the proper term for slow heart rate?

Answer 44

bradycardia

Question 45

How does bradycardia show on an ECG?

Answer 45

few cycles per 6 second strip (10 of 6 second strips gives 1 minute & #of cycles per min is rate...so cycles per 6 second strip is multiplied by 10)

Question 46

What does the vector on an EKG represent?

Answer 46

general direction of depolarization in the heart

Question 47

What is the mean QRS vector?

Answer 47

represents general direction of ventricular depolarization (tail is the AV node) & points more toward L

Question 48

What happen if heart is rotated toward R side?

Answer 48

mean QRS vector moves toward R common in tall & slender pts

Question 49

What direction is heart rotated in obese people?

Answer 49

toward L side of pt

Question 50

What is a myocardial infarction?

Answer 50

when 1 branch of coronary arteries is occluded (that area of heart becomes electrically dead)

Question 51

What direction does mean QRS vector point in MI?

Answer 51

points away from infarction

Question 52

What is the normal mean QRS vector?

Answer 52

points down & to L side of pt (in 0-90 degree range)

Question 53

Describe normal position of mean QRS vector

Answer 53

points toward ventricular hypertrophy & away from MI

Question 54

What does lead I pass through?

Answer 54

AV node (R arm is - & left arm is +)

Question 55

What does a positive QRS complex in lead I indicate?

Answer 55

mean QRS vector is pointing to pt L half

Question 56

What does lead I detect?

Answer 56

right axis deviation

Question 57

What does a positive QRS complex in lead AVF indicate?

Answer 57

downward pointing mean QRS vector

Question 58

What does you want to see for lead I & lead AVF in normal pt?

Answer 58

lead I should point left & lead AVF should point down (in normal quadrant!) indicates ventricular depolarization moving down & left

Question 59

What is left axis deviation?

Answer 59

lead I & lead AVF point upward & to left

Question 60

When do you see left axis deviation?

Answer 60

lead I QRS is positive & lead AVF QRS is negative

Question 61

What should lead V2 always be?

Answer 61

positive (just anterior to AV node)

Question 62

How does lead V2 split the body?

Answer 62

front half is positive & back half is negative (center of sphere is still the AV node)

Question 63

Why is QRS lead in V2 negative usually?

Answer 63

mean QRS vector should point backward b/c of general posterior position of thick L ventricle