Lecture 5 – ECG (Electrocardiogram)

Question 1

12 leads ECG

Answer 1

On sheet

Question 2

Sinus rhythm (2)

Answer 2

A normal heart beat with respect to heart rate and rhythm.

Originates from sinus node.

Question 3

Electrical anatomy steps (4)

Answer 3

SAN –> AVN
via Bachmann’s bundle and internodal pathway

AVN –> Bundle of His
after a slight delay allows ventricles to fully fill, 200ms.

Bundle of His –> Purkinje fibres
Depolarisation of interventricular septum

Purkinje fibres –> Apex

Ventricular depolarisation

Question 4

Categories of arrhythmias (2)

Answer 4

Conduction abnormalities - blocks

Abnormal pulse initiation - ectopics/VT

Question 5

Arrhythmias - Conduction abnormalities (2)

Answer 5

SA block - SA fails to initiate impulse - so no - wave/QRS complex. R-R Irregular.
Ischaemic heart disease.
Valve fibrosis.

AV - AV delay/ interuption in contraction. 3rd degree - ventricles don’t contract. 2nd degree - 2 P waves and 1 QRS complex.
Pacemaker as treatment.

Question 6

Arrhythmias - Abnormal pulse initiation (5)

Answer 6

Ventricular tachycardia - >100 bpm. Monomorphic VT. Wide QRS complex.
Hypotension/Collapse/Acute heart disease.

Ventricular fibrillation - Uncontrolled contraction.
Defibrillator.

Atrial fibrillation - No distinct P wave. Abnormal R-R. Fibrillation wave.

Atrial flutter - R-R Irregular.

SVT- Chronic heart disease. 75% women

Question 7

ECG changes - Myocardial ischaemia (4)

Answer 7

ST depression caused by injury.
Shortage of oxygen.
Reduced membrane potentials - the difference between healthy and myocardial ischaemia potential displaces ST segment.
Injury current effect.

Question 8

ECG changes - MI (Myocardial infarction) (3)

Answer 8

Ischaemia - ST wave depression. -/+ T wave inversion, due to altered repolarisation.

Injury - ST-segment elevation +/- loss of R wave.

Infarction - Deep Q waves due to absence of depolarisation current from dead tissue.