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7. Vascular > Approach to ECG > Flashcards

Approach to ECG Flashcards

1
Q

What are the first three steps of ECG interpretation?

A
  1. Rate
  2. Rhythm
  3. Axis
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2
Q

How would you calculate ventricular rate on an ECG?

A

Take the number of large squares on ECG paper in 1 minute (300) and divide by the number of squares between two sequential R waves

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3
Q

How would you assess rhythm?

A

Look at rhythm strip: lead II

Should be defined as regular, regularly irregular, or irregularly irregular

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4
Q

What does the axis represent in an ECG?

A

Since the left ventricle makes up most of the heart muscle under normal circumstances, normal cardiac axis is directed downward and slightly to the left:
Normal Axis = QRS axis between -30° and +90°.

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5
Q

How would you assess axis in an ECG?

A

Look at lead 1 and aVF (quadrant method)

  1. QRS wave should be positive (R wave should be more positive than S is negative)
  2. Should be done in lead 1 and aVF
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6
Q

How would you assess the P wave?

A

Best seen in lead II

Should precede each QRS complex

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7
Q

What are P-wave abnormalities?

A
  1. P-mitrale – elongation of the P-wave (>120 ms) due to left atrial enlargement
  2. P-pulmonale – increased amplitude of the P-wave (>2.5 mm) due to right atrial enlargement
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8
Q

How would you assess the PR interval?

A

Should have a consistent duration

Shortening (<120 ms) suggests an accessory pathway bypassing the AV node

Elongation (>200 ms) suggests impaired AV conduction

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9
Q

What does PR shortening suggest?

A

An accessory pathway bypassing the AV node

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10
Q

What does PR elongation suggest?

A

Impaired AV conduction

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11
Q

How would you assess the QRS complex?

A

Normally consistent amplitude within leads

Elongation (>120 ms) suggests delayed conduction within the His bundle or Purkinje fibres

Increased amplitude suggests ventricular hypertrophy or abnormal ventricular conduction

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12
Q

What are causes of QRS elongation?

A
  1. Left bundle branch block
  2. Right bundle branch block
  3. Ventricular origin
  4. Idiopathic ventricular conduction delay
  5. Hyperkalaemia
  6. Ventricular paced rhythm
  7. Ventricular pre-excitation (WPW pattern)
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13
Q

How would you differentiate between left and right bundle branch block?

A

If the QRS complex is widened and downwardly deflected in lead V1, a left bundle branch block is present.

If the QRS complex is widened and upwardly deflected in lead V1, a right bundle branch block is present.

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14
Q

How would you assess the ST segment?

A

Should be isoelectric, elevation/depression suggests pathology

Pathological deviation usually presents in adjoining leads

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15
Q

What are causes of ST elevation?

A
  1. Infarction
  2. Pericarditis
  3. Bundle branch block
  4. LV aneurysm
  5. Brugada syndrome
  6. Benign early repolarization
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16
Q

What artery do leads II, III and aVF represent?

A

Inferior

Right coronary artery

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17
Q

What artery do leads V1 and V2 represent?

A

Septal

Left coronary artery

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18
Q

What artery do leads V3 and V4 represent?

A

Anterior

Left anterior descending artery

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19
Q

What artery do leads V5, V6 and I represent?

A

Lateral

Left circumflex

20
Q

How would you assess the T-wave?

A

Should be positive in most leads

Normally negative in aVR and V1 (occasionally V2)

21
Q

In what leads could the T wave be negative (physiologically)?

A

aVR and V1

22
Q

How long is a normal PR interval?

23
Q

How long is a normal QRS?

A

Narrow (<100 ms), normal amplitude

24
Q

What does inhalation do to heart rate?

A

Inhalation decreases vagal tone, increasing heart rate

25
What does exhalation do to heart rate?
Exhalation increases vagal tone, decreasing heart rate
26
What happens during blood pressure during inspiration?
Goes down
27
What happens during blood pressure during expiration?
Goes up
28
What are abnormal cardiac axes?
Left Axis Deviation = QRS axis less than -30°. Right Axis Deviation = QRS axis greater than +90°. Extreme Axis Deviation = QRS axis between -90° and 180° See lead I as -90 to +90 (vertical half) See lead aVF as 0 to 180 (horizontal half)
29
If lead I is positive and aVF is negative, what is the deviation?
Possible Left Axis Deviation
30
If lead I is negative and aVF is positive, what is the deviation?
Right Axis Deviation
31
If lead I is negative and aVF is negative, what is the deviation?
Extreme Axis Deviation
32
What are causes of Left Axis Deviation?
Left ventricular hypertrophy Left bundle branch block Inferior MI Wolff-Parkinson-White Syndrome
33
What are causes of Right Axis Deviation?
``` Right ventricular hypertrophy PE Lateral STEMI COPD Hyperkalaemia ```
34
What are causes of Extreme Axis Deviation?
Ventricular rhythms – e.g.VT, AIVR, ventricular ectopy Hyperkalaemia Severe right ventricular hypertrophy
35
In what condition are p waves often absent?
Atrial fibrillation
36
What are the normal durations of the interval in waves?
PR: 120-200 ms (3-5 small squares) QRS: <120 ms QT: <45ms in men; <47 ms in women
37
What is a normal R wave amplitude in I, II and III?
< 20 ms
38
What does an isolated Q wave in lead III present?
Respiration
39
What are causes of pathological Q waves?
Left-sides pneumothorax Dextrocardia Perimyocarditis Cardiomyopathy
40
What are delta waves associated with?
WPW Slurred upstroke of QRS complex
41
What are tall T waves associated to?
Hyperkalaemia Hyperacute STEMI They are tall if - > 5mm in the limb leads AND - > 10mm in the chest leads
42
What causes biphasic T waves?
Ischaemia and hypokalaemia
43
What causes U waves?
Hypothermia Electrolyte imbalances Antiarrythmic therapy (digoxin)
44
How would diagnose first degree heart block on an ECG?
fixed prolonged PR interval (>200 ms)
45
How would diagnose second degree (2.A) heart block on an ECG?
Progressive prolongation of the PR interval until eventually the atrial impulse is not conducted and the QRS complex is dropped AV conduction is picked up after
46
How would diagnose second degree (2.B) heart block on an ECG?
Consistent PR interval duration with intermittently dropped QRS complexes due to a failure of conduction The intermittent dropping of the QRS complexes typically follows a repeating cycle of every 3rd (3:1 block) or 4th (4:1 block) P wave.
47
How would diagnose third degree heart block on an ECG?
No AV association Narrow-complex escape rhythms (QRS complexes of <0.12 seconds duration) originate above the bifurcation of the bundle of His Broad-complex escape rhythms (QRS complexes >0.12 seconds duration) originate from below the bifurcation of the bundle of His

7. Vascular (15 decks)

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