ECG Flashcards

1
Q

How does an atrial or ventricular muscle cell depolarise

A

+ve/-ve charge movement through gap junctions from previously depolarised cell
+ve charge flows through the gap junctions and depolarises the next cell

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2
Q

Sinus arrythmia

A

vagal activity is proportional to 1/HR

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3
Q

What is a 1st degree nodal block

A

If the conduction velocity through the AV node is slowed due to injury, PR interval will be lengthened (> 0.2s, as normal is 0.12-0.2s)

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4
Q

What is a 2nd degree nodal block

A

If AV node conducts only some of the supra-ventricular depolarisations => not all P waves will be followed by QRS complexes (3:2 or 2:1)

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5
Q

What is a 3rd degree nodal block

A

Complete electrical block between atria and ventricles
AV nodes fail to conduct any signals
P wave occurs regularly
QRS waves occur but with decreased force (secondary pacemaker)

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6
Q

What is a Premature Ventricular Contraction

A

Heartbeat normally originates within the atria @ SA node but in abnormal situations (e.g. acute myocardial ischaemia) heart beat may originate in ventricle
PVC not preceded by P wave as the origin is VENTRICULAR

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7
Q

What sort of beat is PVC associated with

A

ECTOPIC
Diastolic interval after PVC is long
Compensatory pause allows for increased ventricular filling before next beat

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