Electrocardiogram Flashcards by Neil Srivastava

What is an EKG

Representation of the electrical events of the cardiac cycle

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What is an arrythmia

Tachycardia, Bradycardia or fibrillation

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What are the electrodes attached to the surface detecting

Depolarisation in the heart chambers

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SA Node rate

60-100 bpm

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AV Node rate

40-60 bpm

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Ventricular cell rate

20-45bpm

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Pacemaker cells of the heart

SA
AV
Ventricular

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What is the standard calibration of the ECG

25 mm/s

2. 0.1 mV/mm

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What do we see if the electrical impulse travels towards the electrode

A positive deflection

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Describe the physiological process happening from the p-wave through the QRD complex

SA Node
AV Node
Bundle of His
Bundle Branches
Purkyne fibres

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What does the P wave show

atrial depolarisation

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What is the PR interval

Atrial depolarisation AND delay in AV Node

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What does each small box on ECG paper represent horizontally

0.04 s

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What does each large box represent on an ECG paper

0.20 s

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What does each large box on ECG paper represent vertically

0.5 mV

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What are EKG leads needed for

Measure the difference in electrical potential between two points

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What are bipolar leads

Two different points on th body

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What are unipolar leads

One point on the body and a virtual reference point with 0 mV, located in the centre of the heart

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How many leads does an EKG have

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What are the 12 leads of a EKG

Standard Limb
Augmented Limb
Precordial leads

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How are the precordial leads subdivided

Septal - V1 +2
Anterior - V3 + 4
Lateral - V5 + 6

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Describe the placing of the four precordial leads

Fourth Intercostal Space right of the sternum - V1
Fourth Intercostal space to the left of the sternum - V2
Directly between leads V2 + V4 - V3
Fifth intercostal space at left midclavicular line - V4
Level with Lead V4 at left anterior axillary line - V5
Level with lead V5 at left midaxillary line - V6

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What are the four lateral leads

V5, V6, aVL, I

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What are the three inferior leads

III, II, aVF

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What should the normal PR interval be

120-200 ms (3-5 squares)

What should the width of the QRS complex be

less than 3 little squares (less than 110ms)

What should the QRS complex look like in leads I and II

Upright

What should the QRS and T waves have in common in all limb leads

The same general direction

What do all waves in aVR look like

Negative

What should happen to the R wave from V1 to V4

Should grow in each reading

What should happen to the S waves from V1 to V3

Must grow in each reading

What should happen to both the R and S wave in V6

They should disappear

What should we see in a normal ST segment and where is the exception

Should be isoelectric EXCEPT for V1 and V2 where it may be elevated

In what leads does the P wave be upright in

I, II, V2 to V6

What should the Q wave be in appearance in I, II, V2 to V6

Not smaller than 0.04 s in width

What should the T wave look like in leads I, II, V2 to V6

Must be upright

Where is P wave always positive

I and II

Where is P wave negative

aVR

How long should the p wave be

less than 3 small squared in duration

What should be the amplitude of a p wave be

Less than 2.5 small squares

What is a sign of right atrial enlargement

Tall (more than 2.5 squares tall) and POINTED p waves

What does left atrial enlargement look like

M shaped P wave in limb leads

What does a short PR interval indicate

WPW syndrome

What does a long PR interval indicate (longer than 200ms)

First degree heart block or hypokalemia

What does a short PR interval indicate (less than 120 ms)

WPW Syndrome

Why would the PR interval be short physiologically

Accessory pathway (Bundle of Kent) allows early activation of the ventricle

Where may NON-PATHOLOGICAL q waves be seen

I, III, aVL, V5 and V6

R wave in lead V6 vs V5

Smaller

What should the depth of the S wave in the QRS complex normally be

30 mm or less

What is a pathological Q wave in the QRS complex

Greater than 2mm deep and 1mm wide

What characteristics in an EKG would indicate LEFT VENTRICULAR HYPERTROPHY

S in V1 + R in V5/6 is greater than 35 mm R wave of 11 to 13 mm in aVL

What is a pathological ST segment

Elevation by 1mm or more

What is the J segment

Point between QRS and ST segment

What does a normal T wave look like

Asymmetrical (first half is more gradual) At least 1/8 but less than 2/3 of the amplitude of R Same direction as QRS

What is an abnormal size for a T wave

10mm or more

What do abnormal T waves look like

Symmetrical Tall Peaked Biphasic or inverted

Where is the QT interval usually investigated

In lead aVL as Uwave is not prominent (very small)

What is the QT interval

Total duration of depolarisation and depolarisation

What happens to the QT interval when HR increases

It decreases

What is the QT for 70 bpm

Less than 0.40 s

What should a normal QT interval be

0.35-0.45 s

What is U wave

After depolarisation which follow depolarisation

What do U waves look like

Small, round and symmetrical

In what lead are U waves positive

Amplitude of a U wave

Less than 2mm

When are U waves more prominent

As heart rate slows

How do we calculate heart rate from an EKG for regular rhythms

Count the number of big boxes between TWO QRS complexes and divide 300 by the number

How do we calculate heart rate from an EKG for irregular rhythms

Count number of beats present on EKG and * by 6

What is the QRS axis

Represents overall direction of the heart's electrical activity

What do abnormalities in the QRs complex hint at

Ventricular enlargement | Conduction Blocks

What does the normal QRS axis run from

-30 to +90 degrees

What is Left axis deviation

-30 to - 90

What is right axis deviation

+90 to +180

What is the equiphasic approach to determining the QRS axis

Locate the most isoelectric limb lead and identify a second lead 90 degrees away from original Determine if lead shows a positive or negative QRS

Symptoms of AF

1. Asymptomatic 2. Palpitations 3. Syncope 4. Dyspneoa 5. Chest pains

What features of an ECG allow us to see an AF

1. NO P WAVE | 2. Irregular heart rate

How is AF managed

1. If acutely needed: Heparin > warfarin 2. If chronic: Warfarin > Heparin CARDIOVERSION ABLATION techniques (removing cells causing AF)

What is cardioversion

Conversion of irregular heartbeat to normal heartbeat using AMIODARONE etc (anti-arhythmic drugs) or electrically

Rate control measures for ECG

1. Beta-blockers (BISOPROLOL or ATENOLOL) 2. Calcium-channel blockers (VERAPAMIL or DILIMIAZEM) 3. Digoxin

What type of heart disease is atrial flutter

Supraventircular tachycardia

What causes atrial flutter

CAD High BP Cardiomyopathy

Atrial Flutter ECG

Saw tooth (jaggered) P waves P:QRS ratio is 2:1

Atrial rate in Atrial Flutter

300 BPM

What is sinus tachycardia

Basically heart is in rhythm (everything’s fine) BUT qrs complexes are very frequent