ECG basics

Question 1

If the PR (atrial) rate was 80 per min and the QRS (ventricular) rate was 45 per min what block would you suspect?

Answer 1

3rd-degree block

Question 2

Where do you measure the PR interval from and to?

Answer 2

The beginning of the P wave to the beginning of the QRS complex

Question 3

What is the most likely rhythm?

Answer 3

1st-degree heart block

Rate: ~80bpm (300/3.6)

Rhythm: regular

QRS: Narrow (<3 small squares)

P-waves: Constantly prolonged (> 5 small squares)

Question 4

How would you calculate the rate on a rhythm strip?

Answer 4

300 divided by the number of large square between consecutive R waves

or

1500 divided by the number of small squares between consecutive R waves

or

Number of R waves across the bottom of a standard 12 lead ECG (10 seconds) multiplied by 6

Question 5

What common arrhythmias have a broad QRS complex?

Answer 5

Ventricular in origin

Ventricular tachycardia (VT)

3rd degree hear block

Conduction

Left bundle branch block (LBBB)

Right bundle branch block (RBBB)

Question 6

If the PR interval was…

5 small squares with every 4th beat dropped…

what type of block would you suspect?

Answer 6

2nd-degree block

Mobitz II

Question 7

Whats the most likely rhythm?

Answer 7

Normal Sinus Rhythm (NSR)

Rate: ~90 (300/3.3)

Rhythm: regular

QRS: narrow (<3 small squares)

P waves: P-R interval normal and constant (3-5 small squares)

Question 8

Describe 1st-degree heart block

Answer 8

Prolonged PR interval > 0.2 sec (5 small squares).

Question 9

If the PR interval on you ECG was…

4 small square then 5 small squares then 6 small squares then 7 small squares then QRS missing…

what type of block would you suspect?

Answer 9

2nd-degree block

Mobitz I (Wenckebach)

Question 10

Define a Q wave

Answer 10

The negative (downward) deflection PRECEDING an R wave

Question 11

What are the criteria for right bundle branch block (RBBB)

Answer 11

Broad QRS

RSR pattern in V1 (2 R waves like an M shape)

Slurred S wave in V6

Question 12

Describe 3rd-degree heart block

Answer 12

No relationship between the P waves and the QRS complexes

QRS rate usually <60 QRS

Width frequently broad (> 3 small squares)

Question 13

Describe 2nd-degree heart block

Mobitz I (Wenckebach)

Answer 13

Ever increasing PR interval until a QRS complex is missed completely and the cycle begins again.

Question 14

Which are the anterior leads?

Answer 14

V1, V2, V3

(some texts consider V1-2 septal and V3-4 anterior)

Question 15

If the PR interval on an ECG was 7 small squares what type of block would you suspect?

Answer 15

1st-degree block

Question 16

Whats the most likely rhythm?

Answer 16

Ventricular Tachycardia (VT/V-Tach)

Rate: ~250 (1500/6)

Rhythm: regular

QRS: Broad (>3 small squares)

P-waves: no

Question 17

Define an R wave

Answer 17

The positive (upward) deflection of the QRS complex

Question 18

Describe 2nd-degree heart block

Mobitz II

Answer 18

A regular PR interval until a QRS complex is missed

Often happens at regular intervals such as every 4th QRS missed

Question 19

Which are the inferior leads?

Answer 19

II, III, aVF

Question 20

Which are the lateral leads?

Answer 20

V4, V5, V6, aVL, I

(some texts consider V3-4 to be anterior and V5-6)

Question 21

What is the normal QRS width?

Answer 21

Less than 0.12 sec (3 small squares)

Question 22

Describe atrial fibrillation (AF)

Answer 22

Irregularly-irregular QRS rate

No clear P waves visible

Question 23

What is the most likely rhythm?

Answer 23

Atrial flutter

Rate: ~150bpm

Rhythm: regular

QRS: Narrow

P-waves: saw-tooth appearance

Question 24

What is the most likely rhythm?

Answer 24

2nd-degree heart block (Mobitz I)

Rate: ~35 - 66 (300/8 to 300/4.5)

Rhythm: Regularly irregular

QRS: Narrow

P-waves: Ever increasing P-R interval until QRS complex dropped

Question 25

What is the voltage criteria for ST elevation?

Answer 25

>1mm above the isoelectric line with the exception of V1 and V2 where >2mm is appropriate

Question 26

What is the normal PR interval?

Answer 26

0.12 - 0.2 seconds (3 - 5 small squares)

Question 27

If lead I is predominantly POSITIVE and lead II is predominantly NEGATIVE what is the cardiac axis likely to be?

Answer 27

Left axis deviation

Question 28

What is the most likely rhythm?

Answer 28

Atrial Fibrillation (AF/A-Fib)

Rate: ~150-300

Rhythm: Irregularly-irregular

QRS: Narrow (<3 small squares)

P-waves: not clearly visible

Question 29

If lead I is predominantly NEGATIVE and lead II is predominantly POSITIVE what is the cardiac axis likely to be?

Answer 29

Right axis deviation

Question 30

Define an S wave

Answer 30

The negative (downward) deflection FOLLOWING an R wave

Question 31

If lead I is predominantly POSITIVE and lead II is predominantly POSITIVE what is the cardiac axis likely to be?

Answer 31

Normal

Question 32

What is the most likely rhythm?

Answer 32

Supra-Ventricular Tachycardia

Rate: ~250 (1500/6)

Rhythm: regular

QRS: Narrow (< 3 small squares)

P-waves: ?

Question 33

Whats the most likely rhythm?

Answer 33

2nd-degree heart block

Rate:

Rhythm: Regular (mostly)

QRS: Narrow (<3 small squares)

P-waves: regular but every 4th beat dropped

Question 34

What are the criteria for left bundle branch block (LBBB)

Answer 34

Broad QRS (>0.12sec)

Dominant S wave in V1

No q wave in V6, I or aVL (high lateral leads)