Electrocardiogram Flashcards
What is an EKG
Representation of the electrical events of the cardiac cycle
What is an arrythmia
Tachycardia, Bradycardia or fibrillation
What are the electrodes attached to the surface detecting
Depolarisation in the heart chambers
SA Node rate
60-100 bpm
AV Node rate
40-60 bpm
Ventricular cell rate
20-45bpm
Pacemaker cells of the heart
SA
AV
Ventricular
What is the standard calibration of the ECG
- 25 mm/s
2. 0.1 mV/mm
What do we see if the electrical impulse travels towards the electrode
A positive deflection
Describe the physiological process happening from the p-wave through the QRD complex
- SA Node
- AV Node
- Bundle of His
- Bundle Branches
- Purkyne fibres
What does the P wave show
atrial depolarisation
What is the PR interval
Atrial depolarisation AND delay in AV Node
What does each small box on ECG paper represent horizontally
0.04 s
What does each large box represent on an ECG paper
0.20 s
What does each large box on ECG paper represent vertically
0.5 mV
What are EKG leads needed for
Measure the difference in electrical potential between two points
What are bipolar leads
Two different points on th body
What are unipolar leads
One point on the body and a virtual reference point with 0 mV, located in the centre of the heart
How many leads does an EKG have
12
What are the 12 leads of a EKG
- Standard Limb
- Augmented Limb
- Precordial leads
How are the precordial leads subdivided
Septal - V1 +2
Anterior - V3 + 4
Lateral - V5 + 6
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
What are the four lateral leads
V5, V6, aVL, I
What are the three inferior leads
III, II, aVF
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
II
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
- Asymptomatic
- Palpitations
- Syncope
- Dyspneoa
- Chest pains
What features of an ECG allow us to see an AF
- NO P WAVE
2. Irregular heart rate
How is AF managed
- If acutely needed: Heparin > warfarin
- 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
- Beta-blockers (BISOPROLOL or ATENOLOL)
- Calcium-channel blockers (VERAPAMIL or DILIMIAZEM)
- 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
