ECG Fundamentals

Question 1

What is the regular axis of the QRS complex?

Answer 1

-30 -> +90 degrees

Question 2

What is the J point on an ECG?

Answer 2

Transition point of QRS complex to ST segment

Question 3

What do each of the main components of an ECG represent?

Answer 3

P Wave: Atrial Depolarisation
QRS Complex: Ventricular Depolarisation
T Wave: Ventricular Repolarisation

Question 4

How long are each of the main ECG intervals meant to be?

Answer 4

PR: 120-200ms (Long shows heart block)
QT: 0.35-0.45s
(QRS Complex less than 110 ms)

Question 5

Where would you place lead 1, 2 and 3 on the ECG?

Answer 5

1: RA -> LA w/ +ve electrode at LA (0deg)
2: RA -> LL w/ +ve at LL (60deg)
3: LA -> LL w/ +ve at LL (120deg)

Question 6

Where would you place the av leads?

Answer 6

avF: 1/2 way between LA and RA to LL w/ +ve on LL (90deg)
avL: 1/2 way between RA and LL to LA w/ +ve on LA (-30deg)
avR: 1/2 way between LA and LL to RA w/ +ve RA (-150deg)

Question 7

How many seconds do squares represent on ECG?

Answer 7

Small: 0.04s
Large: 0.2s

Question 8

Which lead produces all negative waves?

Answer 8

avR

Question 9

Which leads would produce QRS complex upright?

Answer 9

1 and 2

Question 10

In which leads must the R and S waves grow?

Answer 10

R: Chest leads V1 to V4
S: Chest leads V1 to V3 (Disappear in V6)

Question 11

In which leads will T waves and P waves be seen upright?

Answer 11

Leads 1, 2, V2-6

Question 12

What abnormalities on P waves would be shown?

Answer 12

Tall pointed: Right atrial enlargement

M-shaped: Left atrial enlargement

Question 13

What are 3 signs of abnormal T waves?

Answer 13

1) Symmetrical
2) Tall and peaked
3) Biphasic/Inverted

Question 14

What does plateau phase of cardiac AP coincide with on ECG?

Answer 14

QT interval
(QT decreases after HR increases)