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Emergency Medicine > Diagnostics and data interpretation > Flashcards

Diagnostics and data interpretation Flashcards

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Royal College: Emergency Medicine flashcards
1
Q

ECG:

What regions of the heart correspond to which leads?

A
  • Inferior leads: II, III, aVF
  • Lateral leads: I, aVL, V5, V6
  • Anteroseptal leads: V1 (septal), V2 (anteroseptal), V3 & V4 (anterior)
  • Posterior leads (only used if posterior MI is suspected): V7, V8, V9
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2
Q

ECG:

On standard settings, what does each small square (1mm) represent in time (x-axis) and voltage (y-axis)?

A

Standard settings: 25mm/s, 1mV = 1cm

  • Time: 1mm = 0.04s
  • Voltage: 1mm = 0.1mV

Each large square equals:

  • Time = 0.2s
  • Voltage = 0.5mV
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3
Q

ECG:

What are the 10 steps for systematic interpretation of ECGs?

A
  1. Rate
  2. Rhythm
  3. Cardiac axis
  4. P-waves
  5. PR interval
  6. QRS complexes
  7. ST segment
  8. T waves
  9. QT interval
  10. U waves
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4
Q

ECG:

Stages 1 & 2: assessment of rate and rhythm

A

Rate:

  • R-R interval: 300/number of large (5mm) boxes between two R waves
  • Rhythm strip method: the rhythm strip (long one at the bottom) shows 10s. Count # of complexes in the rhythm strip and multiply by 6.

Rhythm:

  • Sinus rhythm has three components: sinus P waves, a regular PR interval, and a QRS after each P wave.
  • Sinus P waves are: positive in I, II and aVF, and negative in aVR
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5
Q

ECG:

Stage 3: assessing cardiac axis (look at the Cabrera circle if unsure)

A

Look at the polarity of leads I and aVF:

  • If both leads are positive, the cardiac axis is between 0° and 90° (i.e. normal)
  • If I is positive and aVF is negative, the axis is between 0° and -90°. In this case, look at II, if this is positive, the axis is between 0° and -30°; if II is negative, the axis is between -30° and -90°, meaning there is LAD
  • If I is negative and aVF is positive, the axis is between 90° and 180°, meaning there is RAD
  • If I and aVF are both negative, there is extreme axis deviation
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6
Q

ECG:
Stage 4: assessing P waves.
Features of a normal P wave?

A
  • Positive in I, II, aVF
  • Negative in aVR
  • Biphasic (i.e. a positive and negative inflection) in V1, with negative inflection < 1mm
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7
Q

ECG:
Stage 4: assessing P waves.
What is P pulmonale? what is it seen in?

A
  • Right atrial enlargement
  • Secondary to COPD, pulmonary fibrosis, pulmonary hypertension, PE etc.
  • Increased amplitude (≥ 0.25mV) in II
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8
Q

ECG:
Stage 4: assessing P waves.
What is P mitrale? what is it seen in?

A
  • Left atrial enlargement
  • Secondary to constrictive pericarditis, rheumatic heart disease
  • Bifid in II (𝗠 shaped → P 𝗠itrale)
  • Biphasic in V1 with negative inflection > 1mm
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9
Q

ECG:
Stage 5: assessing the PR interval;
Normal PR interval?

A
  • Start of P wave to start of the QRS complex
  • Normally 0.12 - 0.20s
  • Should be constant
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10
Q

ECG:
Stage 5: assessing the PR interval;
First-degree AV block diagnosis?

A

Constant PR interval ≥0.20s

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11
Q

ECG:
Stage 5: assessing the PR interval;
Diagnosis of second-degree AV block (Mobitz I/Wenkebach)?

A

PR interval progressively lengthens until a QRS is dropped

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12
Q

ECG:
Stage 5: assessing the PR interval;
Diagnosis of second-degree AV block (Mobitz II)?

A
  • Constant PR interval with QRS complexes intermittently dropped
  • A constant ratio of P waves to QRS complexes (e.g. 2:1, 3:2 etc.)
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13
Q

ECG:
Stage 5: assessing the PR interval;
Diagnosis of third-degree AV block?

A
  • Complete dissociation of atrial and ventricular contractions
  • P waves occurring at regular intervals
  • QRS complexes at regular, slower intervals (around 40bpm)
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14
Q

ECG:
Stage 5: assessing the PR interval;
Causes of PR depression?

A
  • Pericarditis
  • Pericardial effusion
  • Atrial ischaemia
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15
Q

ECG:
Stage 6: assessing the QRS complex;
Normal morphology?

A
  • < 0.1s
  • Q wave < 0.2mV (2 small 1mm squares)
  • Going from V1-V6 𝗦 waves get 𝗦maller, 𝗥 waves 𝗥ise
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16
Q

ECG:
Stage 6: assessing the QRS complex;
What are abnormal Q waves?

A
  • Too deep (≥ 0.2mV)
  • Too wide (≥ 40ms; 1 small square)
  • > 25% of the size of the R wave in V1-V3
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17
Q

ECG:
Stage 6: assessing the QRS complex;
Diagnosis of bundle branch blocks?

A

𝗥ight bundle branch block:

  • 𝗠a𝗥𝗥o𝗪
  • 𝗠 shaped QRS in V1
  • 𝗪 shaped QRS in V6

𝗟eft bundle branch block:

  • 𝗪i𝗟𝗟ia𝗠
  • 𝗪 shaped QRS in V1
  • 𝗠 shaped QRS in V6
  • QRS duration > 0.1s
18
Q

ECG:
Stage 6: assessing the QRS complex;
Causes of dominant R waves?

A
  • R wave prominent from V1-V6
  • Right ventricular hypertrophy
  • RBBB
  • Posterior MI
19
Q

ECG:
Stage 6: assessing the QRS complex;
Causes of poor R wave progression?

A
  • R wave fails to grow from V1-V6
  • S wave may be present in all precordial leads
  • Anterior MI
  • Right heart strain (e.g. massive PE)
  • LBBB
20
Q

ECG:
Stage 6: assessing the QRS complex;
Diagnosis of left ventricular hypertrophy?

A
  • “Sokolov-Lyon criteria”

- S wave depth in V1 + tallest R wave height in V5-V6 > 35 mm

21
Q

ECG:
Stage 7: assessing the ST segment;
Diagnosis of ST elevation?

A
  • ≥ 0.1mV in limb leads
  • ≥ 0.2mV in precordial leads
  • Must be significantly elevated in two contiguous leads
22
Q

ECG:
Stage 7: assessing the ST segment;
Causes of ST elevation?

A
  • 𝗦𝗧𝗘𝗠𝗜: must be reciprocal change (signs of ischaemia i.e. T wave inversion or ST depression) elsewhere on ECG for diagnosis
  • 𝗣𝗲𝗿𝗶𝗰𝗮𝗿𝗱𝗶𝘁𝗶𝘀: global ST elevation (in all territories), may be saddle-shaped. Often no reciprocal change.
  • 𝗕𝗿𝘂𝗴𝗮𝗱𝗮 𝘀𝘆𝗻𝗱𝗿𝗼𝗺𝗲: 2nd commonest cause of sudden cardiac death (after HCM). Coved ST elevation in V1-V2.
  • Coronary artery vasospasm (Prinzmetal’s angina)
23
Q

ECG:
Stage 7: assessing the ST segment;
Causes of ST depression?

A
  • Downsloping depression: myocardial ischaemia/NSTEMI
  • Upsloping depression: with hyperacute T waves = very early MI
  • Upsloping ST depression: digoxin toxicity
  • Flat ST depression: V1-V3 → posterior MI, hypokalaemia
24
Q

ECG:
Stage 7: assessing the ST segment;
Causes of J waves (aka Osborn waves)?

A
  • Hypothermia
  • Brugada syndrome
  • Benign early repolarisation
  • Hypercalcaemia
25
Q

ECG:
Stage 8: assessing T waves;
Abnormalities of T waves?

A
  • Inversion: myocardial ischaemia (cannot localise pathology), ventricular hypertrophy
  • Flattening: myocardial ischaemia, hypokalemia
  • Peaked T waves: hyperkalemia, hypermagnesemia
  • Hyperacute T waves: very early MI
26
Q

ECG:
Stage 8: assessing T waves;
Difference between peaked T waves and hyperacute T waves?

A
  • The total area under peaked T waves is the same as normal (i.e. thin and tall; ‘tented’)
  • Hyperacute T waves have a larger than normal area underneath them (i.e. tall, normal width)
27
Q

ECG:
Stage 9: assessing the QT interval;
Normal corrected QT interval?

A

Men: 390-450ms
Women: 390-460ms

28
Q

ECG:
Stage 9: assessing the QT interval;
Causes of a short QT interval?

A
  • Hypercalcaemia
  • Hyperkalaemia
  • Digoxin
29
Q

ECG:
Stage 9: assessing the QT interval;
Causes of a long QT interval?

A
  • Congenital long QT syndrome e.g. Romano-Ward
  • Drug side effects (e.g. antipsychotics, citalopram, some antibiotics)
  • Hypocalcaemia, hypokalaemia, hypomagnesemia
  • Intracranial pathology e.g. SAH
30
Q

ECG:
Stage 9: assessing the QT interval;
Complications of long QT interval?

A

Torsades des Pointes (polymorphic VT)

31
Q

ECG:
Stage 10: assessing U waves;
What are they and when are they present?

A
  • Small inflection after T wave and before P wave
  • Physiological in bradycardia (become visible when HR < 65bpm; get larger the slower the HR)
  • Also seen in hypokalemia and hypercalcaemia
32
Q

ABG:

6 stages of ABG interpretation?

A
  1. Look at PaO₂
  2. Look at pH
  3. Look at PaCO₂
  4. Look at HCO₃⁻
  5. Calculate base excess
  6. Look at the anion gap (if there’s metabolic acidosis)
  7. Look at the other values on the gas
33
Q

ABG:
Step 1: PaO₂
What is the normal range? What is type 1 respiratory failure?

A
  • Normal = 10 - 14kPa

- T1RF is when PaO₂ is low and PaCO₂ is normal

34
Q

ABG:
Step 2: pH
What is the normal range?

A
  • Normal = 7.35 - 7.45
  • pH < 7.35 = acidosis
  • pH > 7.45 = alkalosis
35
Q

ABG:
Step 3: PaCO₂
What is the normal range? What is type 2 respiratory failure?

A
  • Normal = 4.5 – 6kPa
  • T2RF is when PaO₂ is low and PaCO₂ is high
  • Low PaCO₂ suggests hyperventilation. This can be to compensate for a metabolic acidosis, or it may be psychogenic.
36
Q

ABG:
Step 4: HCO₃⁻
How is this interpreted?

A
  • High: metabolic alkalosis or compensated respiratory acidosis (a very raised carbonate likely indicates chronic acidosis e.g. in a carbon-retaining COPD patient)
  • Normal: uncompensated respiratory disorders
  • Low: metabolic acidosis or compensated respiratory alkalosis
37
Q

ABG:
Step 5: base excess
How is this interpreted?

A
  • Base excess shows how much ‘spare’ HCO₃⁻ is present in the blood.
  • Distinguishes between metabolic acidosis/alkalosis.
  • Only looks at the metabolic component of the blood.
  • Normal range is -2 to 2 mEq/L
  • High base excess → large amount of HCO₃⁻ → ​metabolic alkalosis
  • Low base excess → deficiency of HCO₃⁻ → metabolic acidosis (look at anion gap to determine cause)
38
Q

ABG:
Step 6: anion gap
How is the anion gap measured?

A
  • It is a measure of how many anions that are not routinely tested for are present in the blood
  • Therefore measures how many acids (other than carbonic acid) are present (e.g. lactic acid, ketoacids etc.)
  • (Sum of anions [+ve ions]) - (sum of cations [-ve ions])
  • Calculated as: ([Na⁺] + [K⁺]) - ([Cl⁻] + [HCO₃⁻])
  • Normal anion gap metabolic acidosis: primary (renal or GI) 𝗹𝗼𝘀𝘀 𝗼𝗳 𝗛𝗖𝗢₃⁻ with 𝗰𝗼𝗺𝗽𝗲𝗻𝘀𝗮𝘁𝗼𝗿𝘆 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝗱 𝗖𝗹⁻ 𝗮𝗯𝘀𝗼𝗿𝗽𝘁𝗶𝗼𝗻.
  • Raised anion gap metabolic acidosis: 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝗱 𝗰𝗼𝗻𝗰𝗲𝗻𝘁𝗿𝗮𝘁𝗶𝗼𝗻 𝗼𝗳 𝗼𝗿𝗴𝗮𝗻𝗶𝗰 𝗮𝗰𝗶𝗱𝘀 such as lactate, ketoacids with 𝗡𝗢 𝗰𝗼𝗺𝗽𝗲𝗻𝘀𝗮𝘁𝗼𝗿𝘆 𝗶𝗻𝗰𝗿𝗲𝗮𝘀𝗲𝗱 𝗖𝗹⁻ 𝗮𝗯𝘀𝗼𝗿𝗽𝘁𝗶𝗼𝗻.
39
Q

ABG:
Step 6: anion gap
Common causes of a normal anion gap metabolic acidosis?

A

GI:

  • Diarrhoea
  • Fistulas

Renal:

  • Renal tubular acidosis
  • Addison’s disease
  • Spironolactone

Iatrogenic:
- Saline administration (too much Cl⁻)

40
Q

Chest x-ray:

Systematic method for interpretation?

A
  • Identify the patient and the date of the scan

Assess image quality: 𝗥𝗜𝗣𝗘

  • Rotation
  • Inspiration (5-6 anterior ribs should be visible)
  • Projection (AP/PA film)
  • Exposure (vertebrae should be 𝘫𝘶𝘴𝘵 visible behind heart)

𝗦ome𝗕ody 𝗧ook 𝗠y 𝗟ovely 𝗗inosaur:

  • 𝗦oft tissue (surgical emphysema, ?obese)
  • 𝗕ones (rib fractures, rib notching, other fractures etc.)
  • 𝗧rachea (?deviated)
  • 𝗠ediastinum (aortic knuckle, ?cardiomegaly*, ?pneumomediastinum?
  • 𝗟ungs (?consolidation, ?collapse, ?pneumothorax etc.)
  • 𝗗iaphragm (should be same height, ?blunted costophrenic angle)

*cardiomegaly can only be assessed on a PA film. In this case, the heart should not be more than 50% the width of the thorax.

Emergency Medicine (20 decks)

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