ECG

Question 1

ECG

Answer 1

measures dynamic changes in membrane potential

recording of small extracellular signals produced by movement of APs through cardiac myocytes

Question 2

ECG measures movement of positive charge

Answer 2

propagating depolarization

Question 3

upwards deflection

Answer 3

depolarization moving towards the electrode

Question 4

downwards deflection

Answer 4

depolarization away from the electrode

Question 5

repolarization

Answer 5

toward the electrode

Question 6

lead

Answer 6

difference in voltage

each lead looks at the heart from a unique angle and plane

Question 7

bipolar leads

Answer 7

3 bipolar limb leads

looks at heart in vertical plane

einthoven’s triangle

body is an electrical “volume conductor”

output: voltage difference provides a direct representation of heart’s electrical activity in that lead

Question 8

unipolar leads

Answer 8

3 augmented voltage limb leads

6 precordial or chest leads

measures the electrical potential at one electrode relative to a reference point (often a central terminal)

augmented voltage

circle of axes and einthoven’s triangle

have no negative pole

output: each lead records the potential at one electrode compared to a calculated average of the other two limb electrodes

Question 9

standard bipolar leads

Answer 9

lead 1: RA- to LA +
lead 2: RA- to LL+ (views conducting system)
lead 3: LA- to LL+

Question 10

einthoven’s law

Answer 10

lead 1+lead 3= lead 2 (like vectors)

Question 11

advantages of ECG

Answer 11

simple and cheap

info about:
- anatomical orientation of heart
- chamber sizes
- arrhythmias and conduction blocks (is heart conducting normally)
- myocardial ischaemia (is heart getting enough blood)
- myocardial infarction
- congenital defects (abnormalities)
- changes in cardiac function with time/therapy

Question 12

standard unipolar leads

Answer 12

aVR: RA +ve, (LA+LL) -ve
aVL: LA +ve, (RA+LL) -ve
aVF: LL +ve, (LA+RA) -ve

Question 13

depolarization away from lead

Answer 13

negative deflection

Question 14

depolarization toward lead

Answer 14

positive deflection

Question 15

repolarization away from lead

Answer 15

positive deflection

Question 16

repolarization towards lead

Answer 16

negative deflection

Question 17

chest leads unipolar “precordial”

Answer 17

view heard from horizontal plane

provides a view of the hearts electrical activity from a horizontal plane

provides info about specific areas of heard - good for diagnosing cardiac conditions

takes average of the three limb electrodes

Question 18

standard chest leads

Answer 18

add
V1 and V2 = septal
V3 and V4 = anterior
V5 and V6 = lateral

subtract
take average mean (1,2,3) = center of heart

Question 19

frontal plane leads

Answer 19

lead 1,2,3
aVL,aVR,aVF

Question 20

transverse plane leads

Answer 20

V1-V6

Question 21

what does each type of leads show us

Answer 21

scalar (1D) projection in that plane of the 3-D vector

12 leads allow us to reconstruct the amplitude and direction of this vector

Question 22

right axis deviation

Answer 22

RV hypertrophy
infants
tall and thin
left posterior hemiblock

Question 23

left axis deviation

Answer 23

obesity
pregnancy
left anterior hemiblock
LV hypertrophy

Question 24

extreme axis

Answer 24

dextrocardia
cardiac pacemaker

Question 25

sinus rhythm

Answer 25

normal heart rhythm HR driven by SA node depolarization along normal conduction path subtle changes in HR occurs with each respiratory cycle (inspiration accelerated HR, expiration slows) - deepining of respirations accelerates these changes loss of this rhythm may be seen in diabetes

Question 26

types of altered sinus

Answer 26

mechanisms that vary the firing frequency of the cardiac pacemaker cells pp interval is altered bradycardia Tachycardia respiratory sinus arrythmia

Question 27

tachycardia

Answer 27

increases HR

Question 27

bradycardia

Answer 27

decreases HR

Question 28

respiratory sinus arrythmia

Answer 28

breathing changes alters vagus nerve output

Question 29

atrioventricular conduction blocks

Answer 29

block between AVN and perkinji fibres

Question 30

premature depolarizations

Answer 30

extrasystoles - coupled to normal AP, re-entrant pathway, comes out of no where occurs occasionally in most normal individuals - common in certain abnormal conditions

Question 31

ectopic tachycardias

Answer 31

sporadic ectopic pacemaker AP in a re-entry loop begins and ends abruptly, could be a few beats or for hours, days ( and they often reoccur) happens in ventricles, but more commonly in atria

Question 32

fibrillation

Answer 32

real trouble atrial or ventricular - jiggles (not pumping) multiple re-entry loops uncoordinated contraction - insufficient pumping of blood irregular type of contractions is inefficient in propelling blood probably represents a re-entry phenomenon not pumping blood to the rest of the body

Question 33

right bundle branch block

Answer 33

no organized ventricle repolarizing wide QS slurred S in lateral leads altered T in septal leads

Question 34

acute anterior infarction

Answer 34

in front of heart tissue blocked increased ST in V1-6, 1 and aVL reciprocal ST depression in 2,3 and aVF standing different in resting potential