ECG Interpretation Flashcards
What is important when idetifying an ECG?
Confirm the patients name and age along with the ECG date
What is the standardisation of an ECG?
- 1cm = 1mV
- Paper speed = 25mm/sec
How is the rate of an ECG calculated?
300 divided by the number of big squares per R-R interval
What ECG lead is used to calculate the rate?
Lead II
What is normal rate?
60-100bpm
Bradycardia
<60 bpm
Tachycardia
>100 bpm
What does an ECG record?
electrical impulses start and how they flow through the heart.
Where does the elctrical activity of the heart start?
“internal pacemaker” called the sinoatrial node
What is normal rhythm referred to as?
sinus rhythm
What is conduction?
The way electrical impulses floe through the heart
When should you take an ECG?
- Chest pain
- Palpitations
- breathlessness
- dizziness
- an episode of synocope (blackout)
- unexplained fall
- Stroke
- TIA
What plane do the chest leads look at the heart from?
horizontal
What plane do the 6 limb leads look at the heart from?
vertical
What is sinus rhythm?
- Normal P waves (2.5 boxes)
- Normal QRS complex (3 boxes)
- One P wave followed by one QRS complex
How do you check if rhythm is regular?
Mark position of 3 successive R waves.
Slide the mark forward and check that intervals are equal
Characteristics of Atrial Fibrillation
- No discernible P waves
- Irregular QRS complex
Charactertistics of Atrial Flutter
- P waves can be seen at a rate of 300bpm, giving a saw-toothed appearance
- 4 P waves per QRS complex
- Ventricular activation is regular
Characteristics of Nodal Rhythm
- Normal QRS complex
- P waves are absent
Another name for nodal rhythm
Junctional Tachycardia
Characteristics of Ventricular Rhythm
- two sinus beats and the rate increases to 150bpm
- QRS complex becomes broad and T waves are difficult to identify
- Final beat shows a return to sinus rhythm
What does the P wave represent?
Atrial depolarisation
In what leads in the P wave upright?
- II
- III
- AVF
In what conditions are P waves absent?
- Atrial fibrillation
- Nodal (junctional) rhythm
What is the maximum height of a P wave?
2.5 boxes
What occurs in abnormal P wave; P-Mitrale
2 P waves per QRS complex
What causes a bifid P wave?
left atrial hypertrophy
What occurs in abnormal P waves; P-Pulmonale
P wave is too tall
What causes a peaked P wave?
Right atrial hypertrophy
What is the P-R interval
Bgeining of P wave to the beginning of Q wave
What is the normal range of the PR interval?
120-200ms (3-5 boxes)
What does the PR interval represent
time between atrial and ventricular depolarisation
What does a prolonged PR interval imply?
(>0.2s)
delayed AV conduction
What is defined as the QRS complex?
Beginning of Q to the end of S wave
What is the normal duration of the QRS complex?
0.12s (3 boxes)
What is the normal length and depth of a Q wave?
length = 0.4s
depth = <2mm
What condition(s) are suggested if the QRS complex is 120ms?
- Ventricular conduction defects
- Bundle branch block: left and right
What condition(s) are likely in a low voltage <5mm QRS complex?
- Hypothyroidism
- Chronic obstructuve airway disease
- myocarditis
- pericarditis and pericardial effusion
What are the main features of Left Ventricular Hypertrophy
- R wave in V5 >25mm
- Sum of S in V1 and R wave in V5 or V6 >35mm
- Sokolow-Lyon index
**V5 must not be >25mm
What are the main features of right ventricular hypertrophy?
- Dominant R wave in V1
- T wave inversion in V1-V3 or V4
- Deep S wave in V6
What is a singificant Q wave?
- >40ms (wider than 1 box)
- Depth >2m
When is a significant Q wave present?
- Present couple of hours/day after acute MI
- If present in lead III consider PE
Where is the QT interval measured?
From the start of the QRS compelx to the end of the T wave
QTc =
QT
/RR
What are the causes of a prolonged QT interval?
- Acute myocardial iscaemia
- Myocarditis
- Bradycardia
- Head injury
- Hypothermia
- U&E imbalance
- Congenital
- Drugs
What is the ST segment?
Time from the end of ventricular depolarisation to the start of ventricular repolarisation
What marks the ST segment?
From the end of the QRS complex to the start of the T wave
What is an abnormal ST segemnt
- Elevation >2mm in 2 adjacent chest leads
OR
- Elevation >1mm in 2 adjacent limb leads
What does elevation of the ST segment usually indicate?
INFARCTION
Is the ST segment isoelectric?
Yes
What does the T wave represent?
Ventricular repolarisation
In what leads is the T wave normally inverted?
aVR, V1 and V2 in the young
Where it it abnormal for a T wave to be inverted?
I, II and V4-V6
What does inversion of a T wave indicate?
Ischaemia or infarction
What effect does digoxin have on the T wave?
- T wave inversion
- ST segment sloping depression
Between what axis is the heart normal?
-30 - +90
In what leads are upward deflections present in normal axis
I, II and III
What occurs in left axis deviation and what condition does this indicate?
Negative QRS deflection in II and II
LV hypertrophy and MI
What occurs in right axis deviation and what conditions does this indicate?
Negative QRS deflection in lead I
RV hypertrophy, PE and MI
What 3 changes occur in an ECG during an MI?
- T wave peaking following T wave inversion
- ST segment elevation
- Appearance of new Q waves
What develops in the ECG during a STEMI
- St elevation
- Q wave abnormal, R shortened, T inversion
- ST resolved
- T reverts, Abnormak Q persists
Where can an anterior infract be located?
Any of the percordial leads (V1-V6)
Where can a lateral infarct be located?
Leads I, AVL, V5 and V6
Where can an inferior infarct be located?
Leads II, III, AVF
Where can a posterior infract be located?
Reciprocal changes in lead V1 (ST depression, tall T wave)
Features of an anterior infarction
- Sinus rhythm
- Q waves in leads V2-V4
- Inverted T waves in leads V4-V6
Features of an antero-lateral infarct
- Sinus rhythm
- Q waves in leads I, II, AVL, V3-V5
- Rasied ST segments in leads V2-V6
Features of an inferior infarction
- Sinus rhythm
- Q waves in leads III and AVF
- Depressed ST segments on leads AVL and V6
Features of a PE on an ECG
- LArge S wave in lead I
- Deep Q wave in lead III
- Inverted T wave in lead III
Hyperkalaemia
Tall, tented T wave, widened QRS
Hypokalaemia
Small T waves, prominant U waves
Hypercalcaemia
Short QT interval
Hypocalcaemia
Long QT interval, small T waves