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Anaesthetic FRCA Primary - eLFH Data Interpretation > eLFH - The Electrocardiogram Part 1 > Flashcards

eLFH - The Electrocardiogram Part 1 Flashcards

1
Q

Standard ECG paper speed

A

25 mm/s

= 5 large squares per second

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2
Q

Usual representation of one small square on ECG

A

0.04 s on x axis

0.1 mV on y axis

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3
Q

X and Y axis on ECG

A

X axis = time (s)

Y axis = Amplitude (mV)

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4
Q

Implication of negative deflection vs positive deflections on ECG

A

Negative deflection means electrical impulse is moving away from electrode

Positive deflection means electrical impulse is moving towards electrode

Each lead looks at electrical activity in different plane to the others

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5
Q

Directions of limb lead planes

A

Coronal plane

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6
Q

Direction of chest lead planes

A

Horizontal plane

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7
Q

Bipolar leads

A

Leads I, II and III

Form triangle called Einthoven’s triangle

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8
Q

Unipolar leads

A

Augmented limb leads (aVR, aVF and aVL) and chest leads (V1-V6)

Measured from imaginary reference point of zero potential called the ‘indifferent electrode’ (centre of limb lead electrodes)

Lower amplitude than bipolar leads and therefore need to be augmented

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9
Q

Normal cardiac axis

A

Between - 30 degrees and + 90 degrees

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10
Q

Left axis deviation

A

Between - 30 degrees and - 90 degrees

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11
Q

Causes of left axis deviation

A

Inferior MI

Left anterior hemiblock

LBBB

Pregnancy - mechanical displacement of the heart

Cardiomyopathy

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12
Q

Right axis deviation

A

Between + 90 degrees and + 180 degrees

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13
Q

Causes of right axis deviation

A

RBBB

Right ventricular hypertrophy

Normal variant in young

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14
Q

Causes of right ventricular hypertrophy

A

COPD

PE

ASD

Pulmonary stenosis

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15
Q

Net electrical potential calculation

A

For a particular lead:
Number of small squares positive - number of small squares negative = net electrical potential

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16
Q

Leads commonly used in anaesthesia and why

A

Usually lead II

Gives best visualisation of P wave and QRS to determine rhythm

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17
Q

CM5 configuration of leads use

A

More sensitive to identify ischaemia

Allows detection of 80% of LV ischaemia as it is exploring largest mass of LV muscle

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18
Q

CM5 electrode positions

A

Right Arm electrode placed on manubrium

Left Arm electrode placed on at V5

Left Leg electrode placed on Left Clavicle

Select lead I for monitoring (between Manubrium and V5)

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19
Q

Electrode positioning in cardiac anaesthesia

A

5 electrode ECG monitoring - allows monitoring of a limb lead and chest lead

Usual 3 lead electrodes placed + right leg electrode + choose one from any of V1 to V6

20
Q

Elements of the ECG

A

P wave
Q wave
QRS complex
PR interval
ST segment
T wave
QT interval

21
Q

P wave - represents

A

Atrial depolarisation

22
Q

P wave - size

A

< 0.2 s
< 2.5 mm

23
Q

P wave abnormalities

A

Absence - AF

Flutter waves (saw tooth) - atrial flutter

Hypertrophy:
- Right atrial (P pulmonale)
- Left atrial (P mitrale)

24
Q

Q wave - represents

A

1st downward deflection after P wave

Abnormal in chest leads

25
Q

Q wave - abnormalities

A

Q waves in any lead are abnormal - previous MI with full thickness myocardial loss

26
Q

QRS complex - represents

A

Ventricular depolarisation

27
Q

QRS complex - size

A

< 0.12 s

28
Q

QRS complex - abnormalities

A

Widened QRS - Bundle branch block (right, left and hemiblocks)

Increased height QRS - ventricular hypertrophy

Small QRS - pericardial effusion

29
Q

PR interval - represents

A

Normal delay at AV node

30
Q

PR interval - duration

A

< 0.2 s

31
Q

PR interval - abnormalities

A

Long PR - 1st degree heart block (AV conduction delay)

Short PR - Wolff-Parkinson-White (extra nodal conduction)

32
Q

ST segment - abnormalities

A

ST depression - Reversible ischaemia

ST elevation (>1mm limb leads or >2mm chest leads) - Irreversible ischaemia

Saddle ST elevation - Pericarditis

33
Q

T wave - represents

A

Ventricular repolarisation

34
Q

T wave - size

A

< 5 mm in limb leads
< 10 mm in chest leads

35
Q

T wave - abnormalities

A

T wave inversion (except aVR and V1) - non specific e.g. ichaemia, infection, LVH

Tented T waves - hyperkalaemia

36
Q

QT interval - represents

A

Ventricular refractory period

37
Q

QT interval - duration

A

350 to 430 ms

38
Q

QT interval - correction

A

Bazett’s formula - corrects for HR

QTc = QT / square root RR (s)

39
Q

QT interval - abnormalities (prolonged QT causes)

A

Congenital

Electrolyte disturbance - low K+, low Mg2+, low Ca2+

Drugs

40
Q

Congenital causes of prolonged QT

A

Romano Ward syndrome

Lervell Lange Nielson syndrome

41
Q

Drug causes of prolonged QT

A

Antiarrhythmics class III - amiodarone

Antibiotics - macrolides

Antihistamines

Antipsychotics - phenothiazines

Antidepressants - tricyclic antidepressants

42
Q

Potential additional ECG waves

A

Delta waves

J waves

U waves

43
Q

Delta waves

A

Up-stroking between P wave and QRS complex

Seen in WPW - pre excitatory syndrome

44
Q

J waves

A

Extra deflection at end of QRS complex

Seen in hypothermia < 25 degrees Celsius

45
Q

J waves alternative name

A

Osborne waves

46
Q

U waves

A

Small deflection following T wave

Represents repolarisation of papillary muscles

Seen in hypokalaemia most commonly

47
Q

Causes of U wave

A

Hypokalaemia

Hypercalcaemia

Hyperthyroidism

Digoxin therapy

Anaesthetic FRCA Primary - eLFH Data Interpretation (6 decks)

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