ECG interpretation

Dr. Shamim NassrallyBSc (Hons) MB ChB MRCP(UK)

Clinical Teaching Fellow

Objectives

By the end of this session you should be able to:

Interpret ECGs using a systematic approach

Recognise important ECG abnormalities: acute coronary syndrome acute myocardial infarction common arrhythmias.

Framework

Basic information/Demographics Rate Rhythm Axis P wave and PR interval QRS complex ST segment

Basic information

Identifying information: name/unit number Date/time Voltage (10mm/mV) Speed (25mm/s)

Rate

300/number large squares

Normal: 60-100bpm <60 = bradycardia >100 = tachycardia

Rhythm Are there P-waves? Is each P followed by a QRS? Is each QRS preceded by a P wave?

AF/atrial flutter Supraventricular tachycardias Heart block:

1st degree 2nd degree (Mobitz type 1 and type 2) 3rd degree (complete heart block)

P wave and PR interval

Normal P wave <2.5mm high, <0.11s

Normal PR interval 0.12-0.2s (3-5 small squares)

Axis

I and II positive = normal axis I positive + III negative = left axis deviation I negative + III positive = right axis deviation

QRS complex

Normal QRS <0.12s (3 small squares)

LVH criteria

Wide QRS Left bundle branch block Right bundle branch block

ST segment

ST elevation: MI, left bundle branch block ST depression: ischaemia, posterior MI,

digoxin

T-wave: Tall – hyperkalaemia, left bundle branch block Flat – ischaemia, hypokalaemia

Quiz

Rate Rhythm P wave, PR interval Axis QRS complex ST segment T waves