B1W4 EKG

Question 1

Why is the QRS wave the biggest?

Answer 1

Ventricle=biggest muscle

Question 2

Why don’t we have a wave for atrial repolarization?

Answer 2

It’s covered up by the QRS region

Question 3

How does a single EKG lead record depolarization/repolarization

Answer 3

Records charge on outside of cell

Resting: +

Depolarizing: -

Repolarization: +

Vectors point so head is positive, tail is negative

Question 4

P wave

Answer 4

Atrial depolarization

When SA node fires

Question 5

PR segment

Answer 5

delay of signal at AV node so ventricles can flow

Question 6

PR interval

Answer 6

Full P wave to Q; time needed for atrial contraction and ventricular fill

Question 7

QRS

Answer 7

Ventricular depolarization/contraction

Question 8

ST segment

Answer 8

plateau phase

Due to influx of Ca2+ ions

Question 9

T wave

Answer 9

Ventricular repolarization

Question 10

How to calculate heart rate from EKG

Answer 10

1 small box=.04 seconds

OR do 300/#big boxes between two QRS complexes (get BPM)

Question 11

Standard Leads/Einothan’s Triangle

Answer 11

1: positive on L arm, negative on right arm

1+3=2

Question 12

Way to remember different standard leads and where they go

Answer 12

Left leg is always +

Right arm always -

Left arm varies

Nothing on right leg

Question 13

Unipolar limb leads

Answer 13

AVR: Right arm, +

AVL: left arm, positive

AVF: left foot positive

Question 14

Precordial leads

Answer 14

V1-V3 on atria

V4-V6 on ventricle

Question 15

How to read deflections on EKG

Answer 15

zero deflection=muscle fully depolarized, no current

positive deflection=current towards lead

neg. deflection=current away from lead

Question 16

Normal value for mean axis of heart

Answer 16

-30 to 90

Usually at -60

Question 17

Causes for left axis deviations

Answer 17

• endomorph (short stature)
• pregnancy
• left ventricle hypertrophy due to chronic hypertension (heart has to work harder)
• LBBB

Question 18

Causes for right axis deviations

Answer 18

Ectomorph–tall/thin

hypertrophy of right ventricle, i.e. pulmonary hypertension

RBBB

Question 19

Arrythmias in general

Answer 19

Due to either altered conduction or automaticity

Get abnormal sinus rhythms, shift in pacemaker sites, etc.

Question 20

Conduction problems with arrythmias

Answer 20

SA block–P wave changes

AV block: PQ interval longer

Intraventricular block: QRS changes

Question 21

Arrythmia rhythm problems

Answer 21

• premature depolarization (extra beat)
• ventricular fibrillation (no P or QRS complex, reaaally messed up)
• Atrial fibrillation (atria can’t contract, no P waves)

Question 22

Tachycardia

Answer 22

>100 bpm due to heat, fever, sympathetic stimulation, heart failure

Question 23

Bradycardia

Answer 23

<60 bpm, increases vagal stimulation, athlete’s heart

Question 24

Direction of ventricle depolarization

Answer 24

Apex to base

Base to apex is repolarization

Question 25

Atria depolarization direction

Answer 25

base to apex depolarizes

base to apex repolarizes