ECG basics

Question 1

PR interval

Answer 1

Atrial depolarization and AV nodal delay

over 2 small squares (.12-.2s)

Question 2

QT interval

Answer 2

ventricular depolarization and repolarization 
HR dependent (inversely related to HR)

.44s

Question 3

ST segment

Answer 3

time following ventricular depol where ventricular ejection should occurs

isoelectric

elevation above the isoelectric line= MI or ischemia

Question 4

RR interval

Answer 4

heart rate

increased RR= decreased HR

Question 5

TP interval

Answer 5

when ventricles are relaxing and filling

Question 6

Number of large boxes: Heart Rate

Answer 6

1: 300
2: 150
3: 100
4: 75
5: 60
6: 50

Question 7

Positive voltage deflection

Answer 7

1) depolarization toward a positive electrode

2) repolarization away from electrode

Question 8

Negative voltage deflection

Answer 8

1) depolarization away from electrode

2) repolarization towards an electrode

Question 9

biphasic wave

Answer 9

occur when an electrode is placed perpendicularly to depolarization so it records a positive deflection as it comes toward it and then a negative deflection as it passes by

Question 10

Lead I

Answer 10

LA + AO=0

Left lateral lead
Positive QRS

Question 11

Lead II

Answer 11

LL + AO=60

inferior lead

Question 12

Lead III

Answer 12

LL+ AO= 120

inferior lead

Question 13

aVr

Answer 13

RA + -150deg

Right sided lead

negative QRS

Question 14

AVL

Answer 14

LA + -30deg

Left lateral lead

Question 15

aVf

Answer 15

LL+ 90 deg

inferior lead
biphasic QRS (b/c it is perpendicular)

Question 16

Precordial leads

Answer 16

record electrical activity moving ant/post in the horizontal plane

Question 17

V1

Answer 17

over RV
Right
negative QRS deflections

Question 18

V2 and V3

Answer 18

over IV septum

anterior

Question 19

V4

Answer 19

over apex of LV

anterior

Question 20

V5 and V6

Answer 20

lateral LV

left lateral

Question 21

Anterior leads

Answer 21

V2 V3 V4

Question 22

Left Lateral

Answer 22

I, aVL, V5, V6

Question 23

Inferior

Answer 23

II, III, aVF

Question 24

RV

Answer 24

aVR, V1

Question 25

septal depolarization

Answer 25

IV septum depolarizes first, L to R from LBB visualized as septal Q wave MAYBE seen in Left lateral leads

Question 26

Ventricular depolarization

Answer 26

0-90 deg Positive deflections: I, aVL, II, aVF, III, V5, V6 Negative deflections: aVR, V1

Question 27

R wave progression

Answer 27

Starting with V1, transitions into biphasic in V2-4, and then becoming more positive in V4-V6 transition zone is either in V3 or V4

Question 28

Ventricular repolarization

Answer 28

Positive T wave: I,II,III, aVF, aVL, V5, V6 | Negative T waves: V1 and aVr

Question 29

normal quadrant

Answer 29

AVF mosty + | LL I = +

Question 30

LAD

Answer 30

AVF - LLI + physical shifts (preg, Ob, end of deep expiration, recumbent position) Left ventricular hypertrophy ( Chronic systemic HT, aortic valve stenosis etc) LBB block RV infarc

Question 31

RAD

Answer 31

AVF + LL I - Physical: Tall and lean, deep inspiration, standing RV hypertrophy (Pulmo valve stenosis, pulmonary HT) RBB block LV infarc

Question 32

extreme RAD

Answer 32

AVF - | LL I -

Question 33

RV hypertrophy

Answer 33

large positive deflection of V1 (R wave) | would cause opposite R wave progression (decreases as you go down precordial leads)

Question 34

Left ventricular hypertrophy

Answer 34

Larger than normal amplitude QRS | but fairly normal R wave progression

Question 35

Tachycardia

Answer 35

Elevated HR >100bpm | can be caused by increased HR, increased SNS or toxins, or weakened myocardium

Question 36

QRS complex

Answer 36

<.12 seconds (3 boxes) does not always need a Q wave