Abnormal ECGs Flashcards
What happens to an ECG in AF?
No p wave- just a fluctuating baseline
Pulse and heart rate irregularly irregular because AVN only conducts some atrial depolarisations when not in refractory period.
QRST normal but irregularly irregular
List the different types of heart block.
First degree
Second degree- Mobitz type 1 and Moritz type 2
Third degree or complete (Ventricular escape rhythm needed)
What is ventricular fibrillation and how does it appear on ECG tracing?
VF is abnormal, chaotic, fast depolarisation of the ventricles that arise from multiple ventricular foci. This gives an uncoordinated contraction that leads to quivering ventricles incapable of producing a cardiac output.
Cardiac arrest.
What ECG changes happen in acute MI?
ST elevation
Which ECG changes remain in patients with a history of MI?
Pathological Q waves
What happens to ECGs in ischaemia of the heart?
ST depression
Outline ECG changes that are seen in hypokalaemia.
Low T <3.5mmol/L
U waves <3mmol/L
St deression in <2.5mmol/L
What pacemaker taking over would invert a P wave?
AVN
Why is lead II a good strip?
Often the rhythm strip
Good p wave exposure
Why is lead II a good strip?
Often the rhythm strip (V1, V5 may also be used)
Good p wave exposure
Why are escape rhythms slower?
The SAN node is the fastest
Why are escape rhythms slower?
The SAN node is the fastest pacemaker of the heart so anything replacing it will be slower
Normal QRS with a prolonged PR interval (>5small squares) is….. and is caused by slow conduction in the…. and ….
First degree heart block
AVN and bundle of His
What is Moritz type 1 heart block and what other names does it go by?
Progressive lengthening of PR interval until one P wave does not conduct and make a QRS.
Wenkenbach phenonmenon in 2nd degree heart block
Second degree heart block Mobitz type 2 has what features on ECG
PR interval normal
Dropped QRS complexes
Why is Mobitz type 2 a concern?
High risk for progressing to complete heart block.
What is complete heart block?
Third degree heart block
Normal P wave but not conducted to ventricle
Ventricular pacemaker takes over- slow rate of QRSs and normally wide
No link between P and QRS
How do you treat this degree heart block?
Pacemaker urgently needed
HR too slow to maintain BP and perfusion (cardiogenic shock risk)
What is complete heart block?
Third degree heart block
Normal P wave but not conducted to ventricle
Ventricular pacemaker takes over- slow rate of QRSs and normally wide
No link between P and QRS
P-P interval constant and faster than Q-Q interval which are also constant
What is a ventricular ectopic?
Ectopic foci in the ventricle (foci is an origin of an impulse)
A run on 3 or more ventricular ectopics is called ….
Ventricular tachycardia
What do QRS look like in VT?
Wide - ventricular ectopic not conducted by fast His Purkinje system
A run on 3 or more consecutive ventricular ectopics is called ….
Ventricular tachycardia
Why is VT a dangerous rhythm?
Risk VF
Are all leads affected in MI or cardiac ischaemia?
No just the leads facing affected myocardium
Which leads are affected by a Right coronary artery occlusion?
Right ventricle affected so Inferor facing leads detect change
II, aVF, III
Which leads are affected by a Right coronary artery occlusion?
Right ventricle affected so Inferior facing leads detect change
II, aVF, III
V2 V3 and V4 would be affected in an MI involving which coronary artery?
Left anterior descending
Anterior heart affected
Which artery being occluded would affect the lateral side of the heart? Which leads would show changes?
Left coronary artery
V6, V5 aVL and I
Which area of myocardium is hardest to perfuse?
Endocardium is furthest from coronary arteries
Which area of myocardium is hardest to perfuse?
Endocardium is furthest from coronary arteries so is most vulnerable to ischaemia
Are iscahemic changes always seen on ECG if the heart has iscaemia?
No sometimes the heart only gets ischameic in exercise when the HR increases and systolic time is reduced. The coronary arteries flow in diastole so shorter time to perfuse a heart muscle that needs more oxygen.. ischaemia shown in exercise but not rest.
ST depression and T wave inversion are signs of …
why do you get them?
Ischaemia
Abnormal currents in repolarisation
When do you see ST elevation?
During acute occlusion of a coronary artery lumen by a thrombus.
Full thickness muscle injury
Hours after an MI what do ECGs look like?
ST elevation
Lower R wave
Pathological Q wave
1-2 days post MI the ECG shows?
T wave inversion
Deeper Q wave
ST normalisation with T wave inversion is seen …… post MI
days
What do Pathological Q waves indicate?
Muscle necrosis
How do you know if a Q wave is pathological?
> 1 small sq wide
>2 small sq deep or more than 0.25 the night of the following R
What are the signs of hyperkalaemia on ECG other than high T?
Prolonged PR St depressed Atrial standstill IV block VF
When assessing an ECG what do you comment on?
rhythm rate PR interval QRS int QT int P wave QRS description ST segment position T wave Axis
What is cardiac axis?
Average over all direction of depolarisation spread in ventricles. Normal -30-90 degrees
What can give a left axis deviation?
Problem with LBB
Inferior MI
LVH
RVH shift cardiac axis to the….
right
How do we check if cardiac axis has changed?
Compare is QRS is upright in which leads
QRS upright in lead I but inverted in III and aVF
left deviation of cardiac axis
right axis deviation look like what ?
aVF and lead III are upright QRS but lead I is inverted
How do you remember right and left deviations?
compare avF and Lead I
QRS Leave each other (point in opposite directions) Left
QRS reach together (point toward each other) Right
