The ECG Flashcards by Eilish Smyth

How many electordes and leads are there?

10 electrodes split into 12 leads

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What does aan electorcardiogram measure?

The elctical fields generated by depolarisation and repolarsiation of the cardiac muscle

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What are the different types of leads involved in a electrocardogram?

Unipolar and bipolar leads

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Which are the unipolar leads?

Chest leads VI-V6 and the augmented leads, AUR

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What does a unipolar lead do?

Records from labelled positive electorde and utilise several other electordes, positive and negative

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What are the bipolar leads?

I, II, III

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What do the bipolar leads do?

Using postive and negative elctordes from the standrd limb leads

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What creates a postive deflection on the electrode?

Depolarisation moving towards an electrode

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What causes a negative defelection from the baseline?

Depolarisation moving away from a electorde?

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What does the amplitude of the signal depend on?

How much muscle is depolarising and how directly towards the electrode the exication is moving

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What does the p wave represent?

Atrial depolarisation

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What does the. Q wave respensent?

Septal depolarisation moving towards the ventricle

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What does the r wave repersent?

The main ventricular depolarisation

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What does the s wave repersent?

End ventricular depolarisation

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What does the T wave reperesnet?

ventricular repolarisation

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WhatL are the possible confounders in a ECG?

Lead misplacement, muscle contractions, such as shivering, talking and coughing, and interference from a alternating current and poor electrode contact

What are the different fibres involved in transmitting an electrical impulse in the cell?

The SA node, the inter nodal tracts, the AV node, bundle of His, the left bundle branch, purkinje firbres

What is the lead used to assess the rythum of the ECG?

The lead II rythum strip

How many squares is 1 second?

5 large squares

What are some of the features of atrial fibrillation on a ECG?

Artial depolarisation is chanotic, and therefore there are multiple bumps and no presence of a p wave, the QRS complexes are normal, however they are irregularly irregular

How do you define the P-R interval?

From the start of the p wave to the start of the QRS complex

What are some of the features of a first degree heart block?

There is slow conduction in the Av node and the His bundle, so the PR interval is prolonged to more than 5 small squares, but both the P wave and the QRS complex are normal.

What are the two types of second degree heart block?

Type I mobitx and Type 2 second degree heart block

What are some of the features of type I second degree heart block?

Progressive lengthening of the PR interval, until one p wave is not conducted and the cycle begins again.

What are some of the features of a type II second degree heart block?

The PR interval is normal, but there is sudden lack of conduction of a p wave and has a high risk of progressing to a complete heart block, and therefore requires a pacemaker

What are some of the features of a third degree heart block?

P waves occur at a normal rate but are not conducted to the vetircle, the ventiulr pacemaker takes over resulting is wide QRS complexes and only produced 30-40 bpm, which is too low to maintain adequate Blood pressure and perfusion and requires urgent insertion of a pacemaker

What are ectopic foci?

Abnormal pacemaker sites within the muscle that display automaticity, which are normally suppressed by the higher rate of the SA node.

What are some of the features of venticular ectopic beats?

Eptoc focus is in the ventricle, much slower depolarisation of the ventricle as the depolarisation spreads through the muscle and not the purkinje fibres and therefore this leads to a wide QRS complex/

What are some of the features of ventricular fibrillation?

Impulses arising from numerous eptoci foci in the vertebral muscle, abnormal chaotic and fast ventricular depolarisation, no cordinated contraction, and no pulse generated which leads to cardiac arrest.

How do you assess structural abnormalities within a ECG?

You look at the P QRST in all leads to identify the problem and the affected part of the heart.

What are the views that are provided by the limb leads?

They view the heart in the vertical plane. Leads II, II and aVI view inferior surface of the LV and the RV.

What is ventircular tachycardia?

A run of three or more consecutive eptocic beats

What views of the heart do the chest leads give you?

They show the chest in the horziontal plane, V1 and V2 face the right ventricle, V3 and V4 face the inter ventricular septum, V5 and V6 face the left ventricle

What are the features of a fully evolved myocardial infarction on a ECG?

Q waves due to myocardial necrosis, ST segment elevation due to su epicardial injury and T wave inversion.

What is the axis?

The average direction of spread of ventricular depolarisaiton

What is the angle of the normal cardiac axis?

Between -30 and 90 degrees

What are the abnormal types of cardiac axis?

Right deviation is more than 90 degress, and left axis deviation is more than -30 degrees

What are the features of left axis deviation on a ECG?

Looking at the QRS complexes in Leads I, II and II, lead I is upright and lead II is inverted and therefore they are facing way from one another

What are the features in a ECG that shows Right axis deviation?

The QRS in lead I is predominately negative, and the QRS in lead II is upright and therefore positive, they are sort of reaching to each other