Lecture 13 ECG part 2

Question 1

What causes heart block?

Answer 1

Acute MI and degenerative changes to conduction system etc

Question 2

First degree heart block recognition?

Answer 2

Prolonged PR interval

Question 3

Second degree heart block recognition?

Answer 3

Mobitz Type 1- successively longer PRs until a QRS is dropped

Second degree Mobitz type 2- PR intervals dont lengthen but QRS suddenly dropped (high risk of progression to complete heart block)

Question 4

What is complete heart block?

Answer 4

Complete failure of atrioventricular conduction

No relationship between p waves and qrs

Wide qrs and slow rate

Question 5

How to identify bundle branch block?

Answer 5

Sinus rhythm but with a wide qrs complex

Question 6

Types of abnormal rhythms?

Answer 6

Ventricular and supraventricular, ventricular are more dangerous

Question 7

How to tell supraventricular abnormality from ventricular?

Answer 7

Supraventricular has normal but narrow qrs

Ventricular has widened qrs

Question 8

How to identify atrial fibrillation?

Answer 8

From multiple atrial foci

No p waves just wavy baseline. Qrs complex fine but irregular RR intervals

Atrial contraction lost with irregular pulse and heart rate. Increased risk of blood clotting

Question 9

Ventricular ectopic beats?

Answer 9

Come fromgroup of excitable cells outside SA node.

Wide QRS complex with abnormal shape, last part dips low

Question 10

What is ventricular tachycardia?

Answer 10

Three or more ventricular ectopic beats in a row and has high risk of progressing to VF

Question 11

VF?

Answer 11

No coordinated beats, chaotic and fast depolarisation from multiple ectopic sites. No cardiac output leading to cardiac arrest.

Defibrillation required

Question 12

How to identify ischaemia in heart?

Answer 12

Look at QRST for the lead facing area of ischaemia and will see changes

Question 13

Leads facing different parts of heart?

Answer 13

See lecture

Question 14

stEMI vs NON STEMI MI

Answer 14

StEMI involves a ST being elevated while non stEMI doesn’t

Question 15

StEMI identification?

Answer 15

ST segment elevation in leads facing affected area is earliest sign

Question 16

Why does necrosis cause Q waves?

Answer 16

Dead tissue has no electrical activity so lead views straight to opposite side of heart and electrical forces may move in opposite direction

Question 17

Pathological Q wave?

Answer 17

Greater than 0.04 seconds, more than 2 small squares deep or more than a quarter height of R wave

Question 18

eCG changes due to subendocardial injury?

Answer 18

sT depression and T wave inversion

Unstable angina and NStemi look the same

Use blood test troponin to differentiate

Question 19

How to identify unstable angina?

Answer 19

ECG normal at rest but ST depression during exercise

Question 20

Hyperkalaemia and ECG?

Answer 20

Reduced concentration gradient reduces excitability

Get tall peaked T wave and eventually widened QRS if very high level

Question 21

Hypokalaemia EcG?

Answer 21

Low T wave

Question 22

What blocks have fixed PR intervals and which have variable PR intervals?

Answer 22

Fixed= mobitz type 2 and first degree

Variable- mobitz type 1 and third degree