Lecture 7 - ECG, Electrical Events In The Heart

Question 1

P wave =

Answer 1

Atrial depolarisation

Question 2

P-R (q) interval =

Answer 2

Internal between beginning of excitability of atria and ventricles (0-16s)

Question 3

QRS complex =

Answer 3

Ventricular depolarisation, atrial repolarisation occurs but is obscured

Question 4

Q-T interval

Answer 4

Contraction occurring (0.35s)

Question 5

S-T segment =

Answer 5

All ventricle tissue depolarised, contraction occurring

Question 6

T wave =

Answer 6

Ventricular repolarisation

Question 7

In a healthy individual what is the normal P-R interval in seconds?

Answer 7

0.16 seconds

Question 8

What is the P-R interval important for?

Answer 8

Identifies heart conditions if an individuals P-R interval is longer or shorter than 0.16seconds

Question 9

Why can’t you see atrial repolarisation occurring in the QRS complex?

Answer 9

Can’t see on an ECG because it is obscured by ventricular depolarisation

Question 10

Why is the ST segment a flat line on an ECG?

Answer 10

Because there is no change in the electrical currents

Question 11

What is heart block?

Answer 11

Block of electrical signal between the atria and the ventricles usually in the AV node

Question 12

What are the 3 types of AV heart block?

Answer 12

1st degree heart block, 2nd degree and 3rd degree heart block

Question 13

What is 1st degree heart block?

Answer 13

P-R interval is longer at 0.28 seconds, can count how many squares the P-R interval is (40mmseconds per square)

Question 14

What is second degree heart block?

Answer 14

Characterised by a dropped beat, not every p wave is followed by a QRS complex

Question 15

What is an example of a condition which is classed as second degree heart block?

Answer 15

Atrial tachycardia (atrial flutter)

Question 16

What is second degree heart block free one?

Answer 16

Where there is a QRS complex after every 3rd P wave!!

Question 17

What is 3rd degree heart block?

Answer 17

Complete dissociation between the P wave and the QRS complex, complete block of the AV node

Question 18

What is a condition that is classed as 3rd degree heart block?

Answer 18

Severe myocardial ischemia - need a pacemaker

Question 19

What is the QRS complex like in third degree heart block?

Answer 19

It is fairly regular because the AV node set its own rhythm at 40 action potentials per minute, but this is not sufficient if you need to walk or stand up - you would need a pace maker to increase heart rate

Question 20

What is cardiac arrhythmia?

Answer 20

An abnormal heart rate

Question 21

What is bradycardia?

Answer 21

Heart rate slows (under 60 beats per minute)

Question 22

What is tachycardia?

Answer 22

Heart rate is fast - over 100 beats per minute

Question 23

What is ventricular tachycardia?

Answer 23

When the ventricles are beating abnormally at 100bpm

Question 24

What are the two varieties that an abnormal heat beat can come In?

Answer 24

A regular abnormality or an irregular abnormality

Question 25

What is a regular abnormality?

Answer 25

Atrial flutter

Question 26

What is an irregular abnormality?

Answer 26

Atrial fibrillation

Question 27

How do abnormalities arise?

Answer 27

In the ventricles or supraventricles e.g. the atria or in the AV node

Question 28

Describe atrial fibrillation

Answer 28

Irregular a rhythm in the atria, chaotic ventricle activity in the atria - nothing is coordinated

Question 29

What would you not see in atrial fibrillation?

Answer 29

A Pave - because the atria is not contracting it is chaotic

Question 30

What are some symptoms of atrial fibrillation?

Answer 30

Breathlessness, tiredness and inability to exercise

Question 31

Describe atrial flutter

Answer 31

Regular abnormality - one side of the atrium contracts while other relaxes, has a 2:1 or a 3:1 ECG rhythm

Question 32

What are some treatments for atrial flutter?

Answer 32

Antiarrythmic drugs or cardioversion therapy (electrical shock)

Question 33

Can you live with ventricular tachyacardia?

Answer 33

Yes it is not always life threatening

Question 34

Describe ventricular arrhythmia

Answer 34

Abnormally fast heart rate arising at the AV node, additional pathway between the atrium and ventricle, the p wave is not obvious

Question 35

What are the symptoms for ventricular arrhythmia?

Answer 35

Chest pain, feel weak, breathlessness or lightheaded, feel tired

Question 36

What is the treatment for ventricular tachycardia?

Answer 36

Antiarrhythmic drugs or cardioversion therapy

Question 37

Describe ventricular fibrillation

Answer 37

Chaotic ventricular activity, fatal in 1-3 minutes, uncoordinated ventricular contraction = can’t pump blood around the body. Irregular ECG rhythm, no P wave, broad QRS complex

Question 38

What is the treatment for ventricular fibrillation?

Answer 38

Implantable cardioverter defibrillator (ICD)

Question 39

What does the implantable cardioverter fibrillator do?

Answer 39

If you heart stops it will defibriallate it and it sets a normal sinus rhythm at 72 beats per minute

Question 40

What is an example of a class I antiarrhythmic drug?

Answer 40

Na+ channel blockers

Question 41

What is an example of class II antiarryhtmic drugs?

Answer 41

Beta blockers (anti-sympathetic) - they block the beta 1 receptors

Question 42

What do beta blockers affect?

Answer 42

The time between each action potential

Question 43

What are class 3 antiarrythmic drugs?

Answer 43

K+ channel blockers, affect when there is repolarisation

Question 44

What are class IV antiarryhtmic drugs?

Answer 44

Ca2+ channel blockers, affect of the plateau of the action potential, affect whether trigger ca2+ enters for CICR

Question 45

What are class 5 antiarrythmic drugs?

Answer 45

Cardiac glycosides

Question 46

How many types of class 1 are there?

Answer 46

3 - 1a, 1b, 1c

Question 47

What are class Ia?

Answer 47

Moderate blockers, they moderately block the rate of depolarisation which results in an increase of action potentials - used for atrial fibrillation and atrial tachycardia

Question 48

What is an example of class 1a?

Answer 48

Quinidine

Question 49

What is class ib?

Answer 49

Weak blockers, hardly seen an affect, they shorten the action potentials and can be used for in the ventricles

Question 50

What is an example of Ib?

Answer 50

Lidocaine

Question 51

What is class Ic?

Answer 51

A strong blocker, only used for life threatening ventricular diseases as you risk blocking the transmission itself in the ventricles.

Question 52

What is an example of class Ic?

Answer 52

Flecainide

Question 53

What class is more favourable for treatment?

Answer 53

Class III - K+ blockers, as you slow down the rate of repolarisation so you don’t affect the rate of depolarisation so no risk of blocking transmission to the ventricles - you get a slower heart rate

Question 54

What is an example of class III?

Answer 54

Amiodarone