Lecture 13 ECG part 2 Flashcards
What causes heart block?
Acute MI and degenerative changes to conduction system etc
First degree heart block recognition?
Prolonged PR interval
Second degree heart block recognition?
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)
What is complete heart block?
Complete failure of atrioventricular conduction
No relationship between p waves and qrs
Wide qrs and slow rate
How to identify bundle branch block?
Sinus rhythm but with a wide qrs complex
Types of abnormal rhythms?
Ventricular and supraventricular, ventricular are more dangerous
How to tell supraventricular abnormality from ventricular?
Supraventricular has normal but narrow qrs
Ventricular has widened qrs
How to identify atrial fibrillation?
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
Ventricular ectopic beats?
Come fromgroup of excitable cells outside SA node.
Wide QRS complex with abnormal shape, last part dips low
What is ventricular tachycardia?
Three or more ventricular ectopic beats in a row and has high risk of progressing to VF
VF?
No coordinated beats, chaotic and fast depolarisation from multiple ectopic sites. No cardiac output leading to cardiac arrest.
Defibrillation required
How to identify ischaemia in heart?
Look at QRST for the lead facing area of ischaemia and will see changes
Leads facing different parts of heart?
See lecture
stEMI vs NON STEMI MI
StEMI involves a ST being elevated while non stEMI doesn’t
StEMI identification?
ST segment elevation in leads facing affected area is earliest sign
Why does necrosis cause Q waves?
Dead tissue has no electrical activity so lead views straight to opposite side of heart and electrical forces may move in opposite direction
Pathological Q wave?
Greater than 0.04 seconds, more than 2 small squares deep or more than a quarter height of R wave
eCG changes due to subendocardial injury?
sT depression and T wave inversion
Unstable angina and NStemi look the same
Use blood test troponin to differentiate
How to identify unstable angina?
ECG normal at rest but ST depression during exercise
Hyperkalaemia and ECG?
Reduced concentration gradient reduces excitability
Get tall peaked T wave and eventually widened QRS if very high level
Hypokalaemia EcG?
Low T wave
What blocks have fixed PR intervals and which have variable PR intervals?
Fixed= mobitz type 2 and first degree
Variable- mobitz type 1 and third degree
