11. Electrocardiography 2

Question 1

Supraventricular arrhythmias

Answer 1

Arrhythmias originating above the AVN

Question 2

Junctional arrhythmias

Answer 2

Arrhythmias originating around AVN (junction between atria and ventricles)

Question 3

Ventricular arrhythmia

Answer 3

Arrhythmia originates from ventricular muscle itself

Question 4

Assessing P-wave and PR interval of an ECG

Answer 4

How long it takes wave of excitation to travel through atrial myocardium
How long it is impeded at the AVN

Question 5

Assessing QRS duration

Answer 5

Broad or narrow?

Question 6

Assessing ST segment

Answer 6

Isoelectric line between S and T wave

Height: is it isoelectric? is it high or low?

Question 7

What are the ECG features of sinus rhythm?

Answer 7

Each P-wave is followed by a QRS wave (1 : 1)
Rate regular (even R-R intervals) and normal (60-90 bpm)

Question 8

What are the ECG features of sinus bradycardia?

Answer 8

Each P-wave is followed by a QRS wave (1 : 1)
Rate is regular (even R-R intervals) and slow (e.g. 56 bpm)
Can be healthy, caused by medication or vagal stimulation

Question 9

How to approximate bpm from an ECG

Answer 9

300 / Number of big squares

Question 10

What are the ECG features of sinus tachycardia?

Answer 10

Each P-wave is followed by a QRS wave (1 : 1)
Rate is regular (even R-R intervals) and fast (e.g. 107 bpm)
Often a physiological response (secondary) e.g. to overactive adrenal gland or hyperactive sympathetic nervous system

Question 11

Rule of hand for calculating left axis deviation

Answer 11

Lead I is positive and lead III is negative for QRS complex

Both Leaving middle of paper

Question 12

Rule of hand for calculating right axis deviation

Answer 12

Lead I is negative and lead III is positive for QRS complex Both Returning to the middle of paper

Question 13

What are the ECG features of sinus arrhythmia?

Answer 13

Each P wave is followed by a QRS wave
Rate is irregular (variable R-R intervals) and normal-ish (65-100 bpm)
R-R interval varies with breathing cycle

Question 14

What are the ECG features of atrial fibrillation?

Answer 14

Oscillating baseline: atria contracting asynchronously
No distinct P waves
Rhythm can be irregular and rate may be slow
Turbulent flow pattern increases clot risk
Atria not essential for filling ventricles: everything else continues

Question 15

What are the ECG features of atrial flutter?

Answer 15

Regular saw-tooth pattern in baseline
Atrial to ventricular beats at a 2 : 1 ratio, 3 : 1 ratio or higher (P : QRS)
Saw-tooth not always visible in all leads

Question 16

What are the ECG features of First degree heart block?

Answer 16

Prolonged PR segment/interval caused by slower AV conduction
Regular rhythm: 1:1 ratio of P-waves to QRS complexes
Most benign heart block, but a progressive disease of ageing
Heart is still an effective pump

Question 17

What are the ECG features of second degree heart block (Mobitz I)?

Answer 17

Gradual prolongation of the PR interval until beat skipped
Most P-waves followed by QRS; but some P-waves are not
Regular irregular: caused by a diseased AVN (There is a pattern, but the pattern is not the same)
AVN not conducting signal like it should

Question 18

What is second degree heart block (Mobitz I) also known as?

Answer 18

Wenckebach

Question 19

What are the ECG features of second degree heart block (Mobitz II)?

Answer 19

P-waves are regular, but only some are followed by QRS
No P-R prolongation, (each P-R is the same)
Regularly irregular: successes to failures (e.g. 2 : 1)
Can rapidly deteriorate into 3rd degree heart block

Question 20

What are the ECG features of third degree heart block (Complete)?

Answer 20

P-waves are regular, QRS are regular, but no relationship
P-waves can be hidden within bigger vectors
Atria and ventricles beat asynchronously
A truly non-sinus rhythm: back-up pacemaker in action

Question 21

What are the ECG features of ventricular tachycardia?

Answer 21

P-waves hidden: dissociated atrial rhythm (Ventricles contracting before EDV is adequate)
Rate is regular and fast (100-200 bpm)
At high risk of deteriorating into fibrillation (cardiac arrest)
Shockable rhythm

Question 22

What are the ECG features of ventricular fibrillation?

Answer 22

Heart rate irregular and >,250 bpm
Asynchronous ventricular contraction: no filling
Heart unable to generate an output = Cardiac arrest
Shockable rhythm

Question 23

What are the ECG features of ST elevation?

Answer 23

P waves visible and always followed by QRS
Rhythm is regular and rate is normal
ST-segment is elevated >2mm above the isoelectric line
Caused by infarction

Question 24

Usual positioning of ST segment

Answer 24

Isoelectric

Question 25

What are the ECG features of ST depression?

Answer 25

P waves visible and always followed by QRS
Rhythm is regular and rate is normal
ST-segment is depressed >2mm below the isoelectric line
Caused by myocardial ischaemia

Question 26

Supra-ventricular arrhythmias:

What are the sinus rhythms?

Answer 26

Normal (sinus)
Fast (tachy-)
Slow (brady-)
Linked with breathing (sinus arrhythmia)

Question 27

What are the 4 types of Junctional arrhythmias?

Answer 27

First degree block
Second degree block (I)
Second degree block (II)
Third degree block

Question 28

What are the 4 types of Ventricular arrhythmias?

Answer 28

Ventricular tachycardia
Ventricular fibrillation
ST elevation
ST depression

Question 29

Assessing rate and rhythm of an ECG

Answer 29

Count gaps between R waves
Is rate normal? (60-90 bpm)
Is rhythm regular or irregular?