Cardiovascular: Session 7

Question 1

What are the causes of abnormal rhythms?

Answer 1

-Abnormal Impulse formation

Abnormal conduction

Question 2

What are supraventricular rhythms?

Answer 2

Rhythms that arise from

• Sinus node
• Atrium
• AV node

Question 3

Where do ventricular rhythms arise from?

Answer 3

Ventricle

Question 4

What is different about ventricular rhythms compared to supraventricular rhythms ?

Answer 4

• From a focus/foci in ventricle
• Conduction not via usual His-purkinje system
• Depolarisation takes longer
• Wide (>3 small boxes) and bizarre QRS complexes

Question 5

What are the characteristic features of an atrial fibrillation ECG?

Answer 5

• No p waves
• Just a wavy baseline
• Narrow QRS complexes

Question 6

What causes atrial fibrillation?

Answer 6

• Atrial depolarisation chaotic. The atria quiver rather than contract
• Impulses arrive at the AV node at rapid irregular rate so only some conducted to ventricle when AV node is not refractory.

Question 7

Pulse and heart rate is irregularly irregular in atrial fibrillation. True/False

Answer 7

True.

Question 8

What happens to ventricles in Atrial fibrillation?

Answer 8

Ventricles depolarise and contract normally.

Question 9

What is a conduction block?

Answer 9

Delay/Failure of conduction of impulses from atrium to ventricles via AV node and bundle of His

Question 10

What are the causes of Heart block?

Answer 10

• Acute myocardial infarction

- Degenerative Changes

Question 11

What does an ECG from first degree heart block appear as?

Answer 11

• P wave normal
• Slow conduction in AV node and his His bundle. P-R interval prolonged. (>5 small squares)
• QRS normal

Question 12

What does an ECG from Mobitz type 1 (2nd Degree heart block) look like?

Answer 12

• Progressive lengthening of P-R interval until one P is not conducted
• Allows time for the AVN to recover and condition begins again
• Cycle begins again

Question 13

What does an ECG from Mobitz type 2 (2nd Degree heart block) look like?

Answer 13

• PR interval normal

- Sudden non-conduction of a beat. Dropped QRS

Question 14

Which type of 2nd Degree heart block has a high risk of progression to complete heart block?

Answer 14

Mobitz type 2

Question 15

What is the mechanism of 3rd degree heart block?

Answer 15

Atrial depolarisation is normal but the impulses are not conducted to ventricle. Ventricular pacemaker takes over so ventricular escape rhythm.

Question 16

What does an ECG of 3rd Degree heart block appear as?

Answer 16

• Slow heart rate
• Usually wide QRS complexes
• No relationship between P and QRS complexes

Question 17

What are the effect of the slow heart rate in 3rd degree heart block? What is the treatment?

Answer 17

Heart rate is often too slow to maintain blood pressure and perfusion.
Urgent pacemaker insertion is required

Question 18

What are ventricular ectopic beats?

Answer 18

Ectopic focus in ventricle muscle. The impulse is nots read via the fast His-prukinje system therefore much slower depolarisation of the ventricle.

Question 19

What are the features of an ECG of a ventricular ectopic beat?

Answer 19

• Wide QRS complex

- Different in shape to usual QRS

Question 20

What is ventricular tachycardia?

Answer 20

Run of more than or equal to 3 consecutive ventricular ectopics is defined as ventricular tachycardia.

Question 21

Why does persistent ventricular tachycardia require urgent treatment?

Answer 21

It is a dangerous rhythm and has a high risk of ventricular fibrillation.

Question 22

What is ventricular fibrillation?

Answer 22

Abnormal, chaotic, fast, ventricular depolarisation. Impulses from numerous ectopic sites in ventricular muscle. This results in no coordination in contraction and the ventricles quiver. The consequence of this is no cardiac output and cardiac arrest.

Question 23

What are the features of an ECG of a patient with ventricular fibrillation?

Answer 23

No discernible PQRS complex.

Question 24

What is the procedure of treatment for patients in ventricular fibrillation?

Answer 24

Require CPR and immediate defibrillation to restore the rhythm.

Question 25

What can cause ischaemia of the heart and myocardial infarction?

Answer 25

Reduced myocardial perfusion due to coronary atherosclerosis.

Question 26

Which region of the heart is most vulnerable to ischaemia and why?

Answer 26

The sub endocardial region is most vulnerable due to being further away from major coronary arteries that lie on the epicardial surface

Question 27

What do leads facing an area of ischaemia in the heart show?

Answer 27

- ST segment depression | - T wave inversion

Question 28

When can most ischaemic ECG changes be seen?

Answer 28

During exercise. If severe there can ischaemic changes at rests well.

Question 29

What is a STEMI?

Answer 29

ST segment elevation Myocardial Infarction

Question 30

What causes a STEMI?

Answer 30

It is due to complete occlusion of lumen by thrombus. The muscle injury extends 'full thickness' from the endocardium to epicardium.

Question 31

What does an ECG of leads facing an area of myocardial infarction show?

Answer 31

ST segment elevation due to abnormal current during repolarisation.

Question 32

What occurs if perfusion isn't returned to the heart tissue?

Answer 32

Muscle necrosis

Question 33

How much time does it take for a Q wave to begin in a STEMI?

Answer 33

HOURS

Question 34

What does a serum potassium of 7, 8, 9, 10 mEQ/L in hyperkalaemia?

Answer 34

``` At 10 (severe), ventricular fibrillation At 9, atrial standstill and intraventricular block At 8, Prolonged PR interval, Depressed ST segment, High T wave At 7, High T wave ```

Question 35

What are the evolving changes in a ST segment elevation MI?

Answer 35

Acute - ST elevation Hours - ST elevation, Decreased R wave and Q wave begins Day 1-2 - T wave inversion, Deeper Q wave Days later - ST normalises, T wave inverted Weeks later - ST & T normal, Q wave persists

Question 36

What happens in heart in hyperkalaemia?

Answer 36

In hyperkalaemia the resting membrane potential is less negative. This inactivates some voltage gated Na+ channels. Heart becomes less excitable as hyperkalaemia worsens. There are conduction problems.

Question 37

What are the ECG changes in hyperkalemia?

Answer 37

At 7 mEq/L - high T wave 8 mEq/L - Prolonged PR interval, depressed ST segment, high T wave 9 mEq/L - P wave absent (Atrial standstill, intraventricular block) 10 mEq/L - Ventricular fibrillation

Question 38

What is the cardiac axis?

Answer 38

The average direction of spread of the ventricular depolarisation. Usually toward and to the left. between -30 to 90 degrees.

Question 39

What is left axis deviation?

Answer 39

When the overall direction ventricular depolarisation is upwards and to the left so less than -30 degrees.

Question 40

What is left axis devation associated with?

Answer 40

- Conduction block of the anterior branch of the left bundle - Inferior MI - Left ventricular hypertrophy

Question 41

What is right axis deviation?

Answer 41

-When overall direction ventricular depolarisation is downwards and to the right (more than 90 degrees)

Question 42

What is associated with right axis deviation?

Answer 42

-Right ventricular hypertrophy

Question 43

What does an upright QRS in lead 1 and an inverted QRS in AVF?

Answer 43

Left Axis deviation

Question 44

What does an inverted QRS in lead 1 and an upright QRS in lead 3 show?

Answer 44

Right axis deviation