6/7-ECGs Flashcards
(40 cards)
What is the normal conduction pattern in the heart?
- electrical activity starts at Sino Atrial Node
- impulse spreads across atria
- impulse delayed at atrio ventricular node to allow complete atrial contraction
- conduction spreads to bundle of His-right/left bundle branch-purkinje fibres to stimulate myocardial contraction
Name the colours and locations of the limb leads
Right upper limb lead - red - right shoulder
Left upper limb lead - yellow - left shoulder
Right lower limb lead - black - right ankle
Left lower limb lead - green - left ankle
Name the colours and locations of the chest leads
V1 - red - 4th right intercostal space
V2 - yellow - 4th left intercostal space
V3 - green - 5th left intercostal space (closest to sternum)
V4 - blue - 5th left intercostal space
V5 - orange - 5th left intercostal space
V6 - purple - 5th left intercostal space (closest to mid clavicular line)
Where can the QRS complex normally be seen?
aVL, I, II, aVF
Which is between -30 and +90 degrees
What is left axis deviation?
Where the QRS complex is present at less than -30 degrees
What causes left axis deviation?
Inferior wall MI
LV hypertrophy
Left anterior bundle block
What is right axis deviation?
Where the QRS complex is found above 90 degrees
What causes right axis deviation?
RV hypertrophy
Acute right heart strain (e.g. Pulmonary embolism)
Left posterior bundle block
What is the standard recording speed of ECGs?
25mm per second
How many seconds are equivalent to big and small squares?
Big square = 0.2 seconds
Small square = 0.04 seconds
Where is the P-R interval measured from and what is the normal range?
Measured from start of p to start of q
Normally 3-5 small squares
What does a long P-R interval indicate?
Indicates a slow atria ventricular conduction, 1st degree heart block
Where is QRS width measured from and what is the normal range?
Measured from start of q to end of s
Normally 2-3 small squares
What does a wide QRS complex indicate?
Indicates abnormal conduction for ventricular depolarisation
Where is Q-T interval measured from and what is the normal range?
Measured from start of q to end of t
Normally 0.35-0.43 seconds
What does a prolonged Q-T interval indicate?
Indicates prolonged repolarisation of ventricles leading to arrhythmias e.g. prolonged QT syndrome
Where is S-T segment measured from?
End of s to start of t
What does a raised or depressed S-T segment indicate?
Should be equal to baseline (isoelectric), raised/depressed indicates ischaemia/MI
What is the equation to calculate a regular heart rate?
No of small squares per minute / no of small squares between peeks
=1500/x
What is needed to be classed as sinus rhythm?
Identical round P waves
Followed by QRS complex every time
Regular rhythm
Why are the depolarisation/repolarisation waves orientated in the same direction?
Repolarisation occurs in opposite direction so usually inverted deflections orientated in same direction
What differences are there between the depolarisation and repolarisation waves?
Repolarisation waves are more prolonged and lower amplitude
What are the features of atrial fibrillation?
Wavy baseline
No p waves
Irregularly irregular rhythm
What causes atrial fibrillation?
Hypoxia Hypertension Sepsis Alcohol Ischaemic heart disease
