ECG abnormalities Flashcards
what are the supraventricular rhythms
rhythms arising above the ventricle so either from the sinus node, the atrium or the AV node
true or false: supraventricular nodes give a wider QRS complex
false - they have a normal, narrow complex as there is still normal ventricular depolarisation
what happens to the QRS complex in ventricular rhythms
it widens as the depolarisation doesn’t conduct through the usual His-Purkinje system and so takes longer
what is atrial fibrillation
where there are multiple atrial impulses and so chaotic atrial depolarisation
what does an ECG look like in atrial fibrillation
no p waves, wavy baseline, normal QRS complexes
true or false - during atrial fibrillation all of the impulses arriving at the AVN are conducted to the ventricles
false - due to the refractory period of the AVN not all impulses will be conducted
how often are impulses conducted to the ventricles in atrial fibrillation
at irregular intervals
what happens to the pulse and heart rate in atrial fibrillation
they are irregular
what is heart block/AV conduction block
where they is a delay or failure to conduct impulses from the atria to the ventricles via the AVN and bundle of His
what causes heart block
- myocardial infarction (e.g. lack of blood supplying the AVN node prevents it from working)
- degenerative changes
how many types of heart block are there
3
what is first degree heart block
where there are prolonged PR intervals which last longer than 5 small squares (0.20 seconds) due to slow conduction
what does an ECG look like in primary heart block
normal p wave
normal QRS
increased PR interval
what is Mobitz type 1 second degree heart block
where the length of the PR interval progressively increases until a QRS complex cant be conducted
what is Mobitz type 2 secondary heart block
where the PR interval is normal and there is a sudden non-conduction of an impulse to the ventricles
what is 3rd degree heart block
where atrial depolarisation is normal but no impulses are conducted to the ventricles
the ventricular pacemaker must then takeover
what rhythm does the ventricular pacemaker give
the ventricular escape rhythm which is very slow and gives a wide QRS complex
why is a pacemaker urgently required in 3rd degree heart block
because the heart rate set up by the ventricular escape rhythm is too slow (30-40bpm) to maintain BP and perfusion
what is an ECG of 3rd degree heart block like
no relationship between p waves and QRS
RR intervals much slower
PP intervals constant
what are ventricular ectopic beats
when there is an opportunistic beat coming from the ventricles
how are ventricular ectopic beats different from the escape rhythm
the ectopic beat is a one off beat that does not occur due to impulse delays
what does the QRS complex look like in a ventricular ectopic beat
wider
what is it called if there are more than 3 consecutive ventricular ectopic beats
ventricular tachycardia which gives a high risk of ventricular fibrillation
what needs to be given during ventricular tachycardia
electrical shock
