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Cardiovascular > ECG > Flashcards

ECG Flashcards

1
Q

What happens in an ECG?

A 
Electrical impulse (wave of depolarisation) picked up by placing electrodes on patient
The voltage change is sensed by measuring the current change
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2
Q

What is the difference between positive and negative deflection?

A 
Positive= electrical impulse ravels towards the electrode
Negative= impulse travels away from electrode
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3
Q

How many leads are there in an ECG?

A

12 leads
6 chest electrodes V1-6/ C1-6
4 limb electrodes- Right arm, Left arm, Left leg, Right leg (Ride Your Green Bike)

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4
Q

What is different about the right leg electrode?

A

Neutral/ dummy

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5
Q

Where is V1 electrode placed?

A

4th intercostal space right sternal edge

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6
Q

Where is V2 electrode placed?

A

4th intercostal space left sternal edge

  • palpate manubriosternal angle of Louis
  • Directly adjacent is 2nd rib with 2nd intercoastal space directly below
  • Palpate inferiorly to find the 3rd then the 4th space
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7
Q

Where is V4 electrode placed?

A

Over apex (5th ICS mid-clavicular line

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8
Q

Where is V3 electrode placed?

A

Halfway between V2 and V4

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9
Q

Where is V5 electrode placed?

A

At same level as V4 but on the anterior axillary line

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10
Q

Where is V6 electrode placed?

A

At the same level as V4 and V5 but on the mid-axillary line

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11
Q

What are the types of leads?

A 
Coronal plane (limb leads)
Transverse plane (chest leads)
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12
Q

What are the types of coronal plane leads?

A

Bipolar- 1, 2, 3

Unipolar- aVL, aVR, aVF

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13
Q

What is the direction of lead 1?

A

Right arm to Left arm

Horizontal

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14
Q

What is the direction of lead 2?

A

Right arm to left leg

Downwards/ diagonal

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15
Q

What is the direction of lead 3?

A

Left arm to right leg

Downwards/ diagonal

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16
Q

What is the direction of aVL?

A

Heart- looking from left shoulder

Heart to left shoulder

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17
Q

What is the direction of aVF?

A

Looking up from feet

Heart to bottom/ in between leg leads

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18
Q

What is the direction of aVR?

A

Looking from right shoulder

Heart to right shoulder

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19
Q

What do each of the chest leads represent/ show?

A 
V1-3= Right ventricle
V4= septum
V5-6= Left ventricle
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20
Q

What is the QRS axis?

A

Represents the net overall direction of travel of the heart’s electrical activity

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21
Q

What can abnormalities of axis hint at?

A 
Ventricular/ structural abnormality
Conduction abnormality (hemiblocks)
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22
Q

Describe the QRS axis

A

Defined as ranging from -30* to +90* (normal)
-30* to-90= Left axis deviation (LAD)
+90 to +180*= Right axis deviation (RAD) (if negative for lead 1= RAD)

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23
Q

What are the limb lead angles?

A 
aVR= -150*
aVL= -30*
Lead 1= 0*
Lead 2= +60*
aVF= +90*
Lead 3= +120*
24
Q

Summary of finding LAD or RAD

A 
Normal= at least positive lead 1 and 2
LAD= positive lad 1, negative lead 2 and 3
RAD= at least negative lead 1, positive lead 3
25
Q

How can you check calibration of an ECG?

A

Look for reference pulse which should appear to be the rectangular wave on the left of the paper
Normal- 10mm tall= 1mV
Y= voltage, X=time
Paper speed= 25mm per seconds so one large box/ 5mm= 0.2 seconds

26
Q

What are the waves and why are they produced?

A

p wave= atrial depolarisation
QRS complex= ventricular depolarisation
t wave= ventricular repolarisation

27
Q

How long should intervals be?

A 
PR= 0.12-0.2 seconds (3-5 boxes)
QRS= less than 0.12 seconds (less than 3 boxes)
QTc= less an 0.44 (m)/ 0.46 (f)- start of QRS to end of t
28
Q

What do the intervals represent/ show us?

A

PR= time to conduct through AVN/ His
QRS= time for ventricular depolarisation- patterns of conductive disease through bundles, RBBB/LBBB
ST segment= start of ventricular depolarisation (should be isoelectric)
T wave= ventricular repolarisation

29
Q

What is ST elevation and depression?

A

ST elevation acute infarction= other things, pericarditis, repolarisation abnormalities
ST depression= ischaemia, LV strain (Left ventricular hypertrophy)

30
Q

What is Wolff-Parkinson-White syndrome?

A

A to V conduction through accessory pathway on rest ECG
Delta wave with short PR interval
Risk of ventricular fibrillation if patient develops atrial fibrillation and if accessory pathway s capable of rapid conduction (tachyarrhythmia)

31
Q

What is Left ventricular hypertrophy?

A

R wave in V5 or V6 plus S wave in V1 greater than 35mm

32
Q

Describe normal ventricular conduction

A

Fibres of Left Bundle Branch begin conduction- impulse travels across interventricular septum from left to right (small r wave V1, small q wave V6)- travels across ventricles causing depolarisation of both RV and LV- LV contributes most to complex (Deep s wave V1, Tall r wave V6)

33
Q

Describe Right Bundle Branch Block (RBBB)

A

V1
No change in initial impulse travel (small r wave)
Impulse depolarises LV by itself since RBBB (s wave)
RV depolarised late by impulse through muscle (r’ wave)
Hence RSR’ pattern (M shape)
MaRRoW pattern

34
Q

Describe Left Bundle Branch Block (LBBB)

A

V1
Initial deflection altered since travels right to left now (Q wave negative deflection)
RV depolarises unopposed (may produce small r wave)
Travels across septum to depolarise LV (deep S wave)
W pattern in V1- WiLLiaM pattern
ST segments uninterpretable

35
Q

Describe ST segment abnormalities

A

Begins at end of QRS complex and ends with the beginning of the T wave
Normally isoelectric line (baseline)
elevation or depression could indicate myocardial ischaemia or infarction

36
Q

Which leads are in which anatomical group?

A 
None- aVR
Lateral- Lead 1, aVL, V5, V6
Inferior- Lead 2, 3, aVF
Septal- V1, V2
Anterior- V3, V4
37
Q

What are the territories for coronary artery supply?

A

Right Coronary Artery

Left Main Stem- Left Anterior Descending, Left Circumflex

38
Q

Describe Anterior ST elevation

A

at least 2mmm from isoelectric line, 2 consecutive leads
Left Anterior Descending Artery occlusion
Inferior

39
Q

Describe Inferior ST elevation

A

Occlusion Right Coronary Artery (80%), Cx 20%
Posterior descending artery
Minority- supplied by left circumflex
1mm in 2 consecutive leads

40
Q

Describe Widespread ischaemia

A

Left Main Stem
Depression
Proximal occlusions as lots of depressions

41
Q

How can you calculate a regular heart rate?

A

Count the number of large squares between R waves (RR interval)
Rate= 300/ no. large squares between R waves

42
Q

How can you calculate an irregular heart rate?

A

Rhythm strip at bottom of 12-lead ECG (10 sec recording of heart)
Rate= number of QRS complexes x 6

43
Q

What is bradyarrhythmia?

A

Any abnormality of cardiac rhythm resulting in a slow heart rate (heart bloc, slow AF) (c.f. sinus brady)
HR less than 60 bpm
AV block

44
Q

What is tachyarrhythmia?

A

Any abnormality of cardiac rhythm resulting in fast heart rate (SVT, uncontrolled AF/Flutter, VT) (c.f. sinus tachy)
HR greater than 100 bpm

45
Q

Describe 1st degree AV block

A

Regular rhythm
PR interval greater than 0.2 seconds and is constant
Ischaemic heart disease (slow HR, beta blockers, calcium acting channel blockers), conduction system disease, healthy children or athletes
Usually does not require treatment

46
Q

Describe 2nd degree AV block- Mobitz 1/ Wenckebach

A

Irregular rhythm
PR interval continues to lengthen until QRS complex missing (non-conducted sinus beat)- PR interval in not constant
Rhythm is usually benign unless associated with underlying pathology (MI)
4:3 Wenckebach (conduction ratio may not be constant)
Progressive prolongation, unconductive into ventricle

47
Q

Describe 2nd degree AV block- Mobitz 2

A

Irregular rhythm
QRS complexes may be wide (greater than 0.12 seconds)
Non-conducted sinus impulses appear at irregular intervals
Rhythm is somewhat dangerous as the block is lower in the conductive system (BB level)
May cause syncope/ may deteriorate into complete heart block
Appearance in setting of acute MI identifies high risk patient
Ischaemic Heart Disease, fibrosis of conductive system
Pacemaker- trigger heart to beat to prevent blackout and complete block
Random non-conducted p wave (2:1/ 3:1), PR interval is constant

48
Q

Describe 3rd degree AV block (Complete heart block)

A

Atria and ventricles beat independent of one another (AV dissociation)
QRS’s have their own rhythm, p waves have their own rhythm (myocardium can generate impulses on its own)
P waves sometimes distort QRS complexes o T waves
May be caused by inferior MI and its presence worsens the prognosis
May cause syncopal symptoms or angina, especially if ventricular rate is low
Usually requires pacemaker+/- temporary pacing/ Isoprenaline

49
Q

What are the types of tachyarrhythmias?

A

Narrow complex

Broad complex

50
Q

Describe narrow complex tachycardia

A

QRS duration less than 0.12s
Uncontrolled atrial fibrillation/ flutter
Atrial tachycardia
AVNRT/ AVRT- above ventricles

51
Q

Describe broad complex tachycardia

A 
QRS duration greater than 0.12s
Ventricular tachycardia
Ventricular fibrillation
Is rhythm from above AVN with BBB/ aberrancy?
In ventricles
52
Q

What is the visual difference between atrial fibrillation and atrial flutter?

A 
Fibrillation= no p waves
Uncontrolled= fast ventricular rate
Flutter= re-entry circuit in right atria- saw tooth conducted in fixed ratio
53
Q

Describe SVT (supraventricular tachycardia)

A

Narrow complex

Accessory pathway forms own circuit

54
Q

Describe ventricular tachycardia

A

Broad complex
Cardiac arrest. cardiovascular collapse
Ant-arrhythmic drugs, cardioversion, defibrillation
No organised electrical activity- no fixed pattern or amplitudes, CPR

55
Q

How to report an ECG

A

Be systematic- Rate, Rhythm, Axis

Go through heart cycle- P wave, PR interval, QRS duration and morphology, T wave and QR interval

Cardiovascular (52 decks)

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