ECG Basics

Question 1

Answer 1

Extracellular membrane potential

Part of the excitable tissue is at different MP than rest of heart

Current flow can occur between areas of different MP

Question 2

Answer 2

Phase 0 atrial muscle, depolarized at end of P wave, atrial muscle AP, atria

Phase 0 ventricular muscle, depolarized in ST segment, ventricular muscle AP

Phase 3 (repolarization) in ventricular muscle, ventricular muscle AP

Question 3

Answer 3

Segment-duration of single event on ECG

Intervals-duration of two or more events on ECG

Horizontally-5 large boxes=1 sec

Vertically-2 large boxes=1.0 mV

Question 4

Answer 4

P wave, QR, 0.16 ms

QR, T wave, 0.35 ms

Question 5

Answer 5

PR SEG-End of atrial depolarization until beginning of QRS

ST SEG-end of WRS until beginning of T wave

Question 6

Answer 6

QRS Complex-1.0-1.5 mv from top of R wave to bottom of S wave

P wave 0.1-0.3 mv

T wave 0.2-0.3 mv

Question 7

Answer 7

Time between dark lines=0.2 sec

Time between light lines=0.04 sec

Question 8

Answer 8

If AP is spreading towards + lead of electrode set, a + deflection will be observed

Question 9

Answer 9

Lead 1 (+=LA)

Lead II (+=LL)

Lead III (+=LL)

avF perpendicular to lead I

avR perpendicular to lead III

avL perpendicular to lead II

Question 10

Answer 10

V1, V2, V3, V4, V5, V6

Question 11

Answer 11

Inferior Leads: II, III, avF

Septal Leads: V1 and V2

Anterior Leads: V2, V3, V4

Lateral Leads: V4, V5, V6, I and aVL

Question 12

Answer 12

Normal mean axis: Leads I and avF are +

Left axis deviation (LAD): + Lead I and - AvF

Right axis deviation (RAD): - Lead I and + AvF

Extreme right axis deviation (Extreme RAD): - Lead I and - avF

Question 13

Answer 13

P wave begins before atrial contraction

QRS complex begins before ventricular contraction

T wave begins before ventricular relaxation