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2 - Sarah's CVS > The Electrocardiogram > Flashcards

The Electrocardiogram Flashcards

(60 cards)

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1
Q

What does the P wave represent?

Why is it a small upward depolarisation?

A

Atrial depolarisation

Due to: smaller muscle mass and depolarisation moving towards the electrode

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2
Q

What does the QRS complex represent?

A

Ventricular contraction

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3
Q

What does Q represent?

A

Septal depolarisation spreading to ventricles

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4
Q

What does R represent?

A

Main ventricular depolarisation

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5
Q

What does S represent?

A

End of ventricular depolarisation

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6
Q

When does atrial repolarisation take place?

A

During the same time as ventricular depolarisation

– during QRS complex

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7
Q

What does the T wave represent?

A

Ventricular repolarisation

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8
Q

Describe the T wave shape

A

Upward signal as repolarisation is away from electrode

Medium sized as timing in the different cells is dispersed

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9
Q

What does the PR interval measure?

A

Time taken for impulse to reach ventricles from the SA node

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10
Q

What is a normal time for a PR interval?

A

0.12 to 0.2 seconds

3-5 small squares

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11
Q

What does a short PR interval indicate?

A

Atria have been depolarised close to the AV node or the is an abnormality of conduction from the atria to the ventricles.

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12
Q

What does the duration of the QRS complex represent?

A

How long excitation takes to spread through the ventricles

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13
Q

What is the normal duration of a QRS complex?

A

0.12 seconds or less

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14
Q

What does a widened QRS complex represent?

A

An abnormality of conduction through the ventricles

E.g. Bundle branch block

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15
Q

What are the V leads?

A

Six chest leads
Made from 6 positions overlying the 4th and 5th rib spaces
– look in horizontal plane from the front and from the left

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16
Q

What do V1 and V2 show?

A

Right ventricle

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17
Q

What do V3 and V4 show?

A

Septum and anterior wall of left ventricle

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18
Q

What do V5 and V6 show?

A

Anterior and lateral walls of left ventricle

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19
Q

What is the cardiac axis?

A

The average direction of spread of the depolarisation wave from the front

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20
Q

Where can you deduct the cardiac axis?

What is the normal shape?

A

From leads I, II and III

Defects signal upwards as depolarisation is spreading towards the three leads

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21
Q

When does right axis deviation occur?

What is it associated with?

A

When the right ventricle becomes hypertrophied.

Usually associated with pulmonary condition putting a strain on the right side of the heart as well as congenital heart defects.

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22
Q

What do you see form the leads in right axis deviation?

A

Deflection in I becomes negative
Deflection in III becomes positive

– axis swings towards the right

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23
Q

When does left axis deviation occur?

What is it usually due to?

A

When the left ventricle becomes hypertrophied

Usually due to a conduction defect
– unlikely to be due to increased bulk of left ventricle

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24
Q

What do you usually see from the leads in left axis deviation?

A

QRS complex become negative in III

Only is significant when QRS deflection is predominantly negative in lead II

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25
What is first degree heart block?
Prolonged PR interval
26
What is first degree heart block a sign of?
Coronary artery disease Acute rheumatic carditis Digitalis toxicity Electrolyte disturbances
27
What is second degree heart block?
Erratic PR interval | Excitations fails to pass through the AV node or the bundle of His
28
What are the causes of second degree heart block?
``` Same as first degree heart block: Coronary artery disease Acute rheumatic carditis Digitalis toxicity Electrolyte disturbances ```
29
What is third degree heart block?
Complete atrioventricular block - - atrial contraction is normal but no beats are conducted to the ventricles - - the two are disconnected electrically
30
How are the ventricles excited in third degree heart block?
By a slow escape mechanism
31
How can you recognise third degree heart block?
P wave rate is normal (90) QRS rate is low (36) No relationship between P and QRS Abnormal shaped QRS complexes due to abnormal spread of depolarisation from ventricular focus
32
What can cause third degree heart block?
Acutely -- transient heart attack | Chronically -- fibrosis around bundle of His
33
When can a right bundle brach block be normal?
When the duration of the QRS complex is normal
34
What do bundle branch blocks indicate?
RBBB indicates problems with the R side of the heart | LBBB always indicates heart disease, usually on the L side
35
What changes occur in the ECG during right bundle brach block?
V1 lead -- normal R wave, second R wave due to failure of conduction pathway V6 lead -- smaller Q wave, normal R wave, wide deep S wave
36
What changes occur in the ECG during left bundle brach block?
V1 lead -- small Q, R wave (inspire of smaller mule mass), S wave (late depolarisation of LV) V6 lead -- R wave, S wave (appears as a notch), second R wave (due to late depolarisation of LV)
37
Where is right bundle brach block most easily seen?
In V1, where there is an RSR pattern
38
Where is left bundle brach block best seen?
In V6 where there is a "rabbit ears" pattern
39
Describe the branching of the bundle of His
From the AV node, two branches arise. The right bundle branch and the left bundle branch. The right bundle branch has no main divisions. The left bundle branch has two main divisions -- anterior and posterior fascicles
40
Which pacemaker cells have priority?
SAN pacemaker cells. They pre-empt other pacemakers due to a faster firing rate.
41
What can you use in order to determine the cardiac axis?
The lead with the smallest possible R wave which will be the lead at 90 degrees to the cardiac axis.
42
When analysing an ECG what do you look for?
``` Rate Rhythm Axis P wave P-R segment QRS complex Q-T interval T wave ```
43
When is the P wave absent?
In atrial fibrillation
44
What are abnormalities that can be seen in the P-R interval?
First degree heart block = prolonged P-R interval Second degree heart block = erratic P-R interval Third degree heart block = no relationship between P and QRS complex
45
What is sinus rhythm?
Pacemaker cells in the SAN are controlling the heart rate | -- normal depolarisation
46
What are the features of myocardial infarction?
ST elevation Pathological Q waves -- greater than one small square across Inverted T waves
47
What changes from the MI are permanent?
Pathological Q waves are permament -- present in full thickness MI -- due to scar tissue forming which effectively blocks the circuit Inverted T waves
48
What do broader QRS complexes represent?
Escape rhythm | -- ventricle is taking over as the pacemaker
49
Where can you see an inferior MI? Which coronary artery is likely to be responsible?
Leads II, III and aVf Right coronary artery
50
Where can you see an anteroseptal MI? Which coronary artery is likely to be responsible?
V1 and V2 Left anterior descending coronary artery
51
Where can you see an anteroapical MI? Which coronary artery is likely to be responsible?
V3 and V4 Distal left anterior descending coronary artery
52
Where can you see an anterolateral MI? Which coronary artery is likely to be responsible?
V5, V6, I, aVL Circumflex coronary artery
53
Where can you see an extensive anterior MI? Which coronary artery is likely to be responsible?
V1 - V6, I, aVL Proximal left coronary artery
54
Where can you see a posterior MI? Which coronary artery is likely to be responsible? Wat are you likely to see in this case?
V1 and V2 Right coronary artery ST depression in anterior leads or as tall R waves
55
Where is the MI if there are changes in leads II, III and aVf?
Inferior
56
Where is the MI if there are changes in leads V1 and V2?
Anteroseptal
57
Where is the MI if there are changes in leads V3 and V4?
Anteroapical
58
Where is the MI if there are changes in leads V5, V6, I and aVL?
Anterolateral
59
Where is the MI if there are changes in leads V1 - V6, I and aVL?
Extensive anterior
60
Where is the MI if there are tall R waves in V1 and V2?
Posterior aspect

2 - Sarah's CVS (13 decks)

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