Physio Test 3 - Cardiac Electrophysiology 2

Front 1

ECG boxes

Back 1

1 small box = 0.04 seconds; 1 large box - 0.2 seconds; 5 large boxes = 1 second

Front 2

p wave

Back 2

small deflection = spread of depol from SA node over atria. electrical representation of atrial systole

Front 3

PR segment

Back 3

brief baseline period btw P wave and QRS complex; results from delay at AV node. Little separation of charge because structures are very close together. .12-.25 seconds

Front 4

PR of greater than .2 seconds indicates

Back 4

1st degree AV block

Front 5

Q wave

Back 5

small neg. deflection due to spread of depol in IV septum; from bundle branches to apical end of septum. L to R.

Front 6

R wave

Back 6

large positive deflection due to spread of depolarization through ventricular apex;

Front 7

S wave

Back 7

small neg deflection; represents later stages of ventricular depol, spreading through L vent wall
- in avf, II, III

Front 8

QRS complex

Back 8

spread of depolarization through ventricles; signals onset of ventricular systole. Should be less than .15 seconds

Front 9

ST segment

Back 9

period at baseline btw QRS and T wave. Time when most ventricular muscle is depolarized; no electrical signal b/c all cells are depolarized and contracting. no separation of charge

Front 10

T wave

Back 10

small, broad deflection due to repolarization of ventricular muscle.
+ in leads I, II
- in leads AVR

Front 11

repolarization direction

Back 11

from epicardium to endocardium; reverse of depol

Front 12

QT interval

Back 12

from start of QRS to end of T wave; duration of ventricular electrical systole

Front 13

Magnitude of electrical ECG signal

Back 13

determined by # of myocytes depolarized and degree of depolarization

Front 14

direction of electrical ECG signal

Back 14

location of depolarized cells and direction of depolarization spread

Front 15

If vector is in same direction as axis

Back 15

positive deflection

Front 16

if vector is oblique to axis

Back 16

only parallel component is recorded

Front 17

if vector is perpendicular to axis

Back 17

no deflection recorded

Front 18

if vector is in opposite direction as axis

Back 18

negative deflection recorded

Front 19

HR and QT inerval

Back 19

QT strongly impacted by HR. Slower HR means longer QT.

Front 20

Mean electrical axis

Back 20

direction of R wave; provides into on spread of depol through ventricles and about the position of the heart in the chest.

Front 21

Normal MEA

Back 21

QRS is + or zero in I, II or AVF and is neg in avr

Front 22

RAD value

Back 22

QRS is neg in I, pos in AVR; R vent hypertrophy

Front 23

LAD value

Back 23

QRS is neg in III, AVF, II; L ventricular hypertrophy

Front 24

sinus bradycardia

Back 24

all complexes evenly spaced, but less than 60 bpm. could be due to increased vagal tone, beta adrenergic blockage, excellent physical conditioning. treat w/ pacemaker if necessary

Front 25

sinus tachycardia

Back 25

all complexes evenly spaced, more than 100 bpm. could be due to decreased vagal tone, excessive adrenergic tone, electrolyte abnormality, CHF, amphetamines, caffeine

Front 26

sinus bradycardia and tachycardia based in

Back 26

SA node

Front 27

ectopic pacemaker

Back 27

rogue part of heart that starts to depolarize from rest during phase 4. could be due to ischemia, electrolyte imbalance, increased catecholamines, etc.

Front 28

premature atrial contractions

Back 28

arise from early sinus beat or ectpic pacemaker in atria. may see some abnormal p waves but most everything else normal. treat w/ beta blocker or Na or Ca channel blocker

Front 29

atrial bigeminy

Back 29

every other beat premature

Front 30

premature ventricular contractions

Back 30

arise from ectopic pacemaker in ventricle; abnormal QRS that is prolonged and has no visible p wave before it.

Front 31

bidirectional block

Back 31

prevents re-entry, not so problematic

Front 32

unidirectional block

Back 32

blocks anterograde signal, but retrograde signal can penetrate through, re-enter loop and activate normal path. leads to regenerative loop of excitation, independent pacemaker circuit. Tachycardia.

Front 33

3 things needed for re-entry loop

Back 33

obstacle to propagation, unidirectional block of impulse propagation, region of slow conductance

Front 34

supraventricular re-entry arrhythmias

Back 34

re-entry circuit around AV node becomes pacemaker; undetectable or inverted P wave.

Front 35

atrial flutter

Back 35

re-entry circuit in atria; rhythmic, high-freq oscillations instead of normal P wave. atrial rate above 200bpm; partial block in AV node may reduce ventricular rate.

Front 36

atrial fibrillation

Back 36

chaotic excitation of atria with coarse or fine oscillations; no detectable p waves. vent rate is variable and set by AV node or ventricular pacemaker

Front 37

1st degree AV block

Back 37

prolonged but uniform PR interval. minor defect.

Front 38

2nd degree AV block

Back 38

worsening of AV conduction; PR interval increases with time until beat is skipped. single p wave not followed by QRS. 2:1 block: every other p wave is followed by QRS.

Front 39

third degree av block

Back 39

complete block at AV node; ventricular rhythm is independent of atrial and is slow. QRS independent of P waves. treat w/ pacemaker.