ECG Flashcards by Ali al-Hussaini

What is the structure for analysing an ECG?

Check patient details and rate of ECG 25mm/s
Rate: 300/R-R interval (big sq.) OR no. QRS x 6 (esp irr)
Rhythm: regular? regularly irregular? irregularly irregular? Is there a P before every QRS? A QRS after every P?
Axis
P wave
PR Interval: should be 3-5 small sq. heart block? degree? type?
QRS Complex: Narrow? i.e. less than 3 small sq.
ST segment:
T waves

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What is the structure for analysing an ECG?

Check patient details &amp; ECG rate
Rate
Rhythm
Axis
P wave
PR Interval
QRS Complex
ST segment
T wave

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What is the number of features you should analyse in an ECG?

Nine

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How do you check patient details and ECG rate?

Check name on ECG is name on folder

Check rate = 25mm/sec

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What is the normal range for heart rate?

60 - 100

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How do you calculate the heart rate?

EITHER

300/no. big squares in R-R Interval

esp. w/ irregular rhythms

no. QRS complexes in rhythm strip/across the ECG times six
(can use lead II, avL, V2, V5 as the width of the ECG should be 10 seconds)

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How do you assess the rhythm?

Check the rhythm is
REGULAR: SINUS RHYTHM
REGULARLY IRREGULAR - note, this can be easy to miss, sometimes the pattern won’t fit into one ECG, but if you had multiple you could see it. e.g. 5 quick beats 2 long beats
IRREGULARLY IRREGULAR - AF : ATRIAL FIBRILLATION

Can you see P waves?

Is each P wave followed by a QRS complex?
Is each QRS complex after a P wave?

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What is supraventricular tachycardia?

SVT is any tachydysrhythmia arising from above the level of the Bundle of His.
e.g. AVN, SAN, AVNRT, AVRT, AF, atrial flutter etc.

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What are the different Intervals of the ECG?

PR Interval: should be 3-5 small squares or less than 1 big square. (120-200ms)
(from start of P to start of QRS)

QRS complex: less than 3 small squares
(less than 120ms)
(from very start of QRS to end of QRS)

QT Interval: less than 2.5 big squares
(less than 450ms)
(from very start of QRS to end of T wave)
(the largest interval)

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How much time is
one big square worth?
one small square worth?

200ms

40ms

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If electrical current moves towards a lead, how is this shown on the ECG?

On that lead, there is an upward deflection.

If the current moves away from a lead, there is a downward deflection.

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If an area of the heart is infarcted, how is this shown on the ECG?

The current moves through this area quicker, so there is a greater upward deflection if the current moves towards this lead. There is a greater downward deflection if the current moves in the opposite direction to a lead.

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What do the chest leads generally (V1-V6) show?

A cross section of the heart.

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What are the general directions of each chest lead?

V1   Septal     (LAD?)
V2   Septal    (LAD?)
V3   anterior  (LAD)
V4   anterior  (LAD)
V5   lateral (left circumflex)
V6   lateral (left circumflex)

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What are the 3 arteries of the heart to remember with ECGs?

Left Anterior Descending Artery
(supplies most of front of heart)

Right Coronary Artery
(supplies right side of heart, inferior of heart (posterior descending artery is a branch) and AVN and SAN)

Right Circumflex Artery
(includes posterior descending artery)

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What are the different types of heart block?

First degree heart block: prolonged PR interval

Second degree heart block: some waves of depolarisation not constricted to ventricles
There are three types of second degree heart block:
Mobitz Type 1: Wenkelbach: Progressive PR prolongation, followed by a non-conducted beat (no QRS for a beat) then pattern repeats (normal PR interval prolonged missed beat cycle repeats)
Mobitz Type 2: most beats conducted but occasional non-conducted beats (occasional QRS complex/beat is missed out)
Fixed Ratio Block e.g. 2:1 alternate conducted and non-conducted beats i.e. 2 normally conducted beats gives 1 conducted beat.

Third degree heart block: no P waves conducted to ventricles i.e. complete heart block i.e. pattern of P waves and QRS are completely independent of each other. Possibly no T waves.

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What are the bearings of the different limb leads?

I	0
II	60
III	120
avR	-150 or 210
avL	-30 or 330
avF	90

(easy to draw the way the av leads are pointing, I, II, III go up in 60s)

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How can you quickly assess Axis Deviation?

Right Axis Deviation
I	down 
II	UP
III	UP
i.e away from 0, towards 60 and 120

Left Axis Deivation
I	UP
II	down
III	down
i.e towards 0, away from 60 and 120=

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What are the boundaries for Axis Deviation?

-30 to 90 is normal

over 180 or -90 is extreme axis deviation

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What are the signs of MI?

ST depression represents posterior STEMI, NSTEMI or ischaemia
ST elevation suggest MI
>1mm in limb leads
>2mm in chest leads
(needs to be tombstone, not high takeoff)
T wave inversion
New left bundle branch block
Tachycardia or Bradycardia

How do you assess PR Interval?

Longer than 5 squares?
Heart block
To which degree?
Which type?

Shorter than 3 squares?
Wolf Parkinson White Syndrome? has an accessory pathway known as the bundle of Kent. Risk of sudden death.

What is often mistaken for ST elevation?

High takeoff, i.e. a concave elevation

Look for a tombstone i.e a convex elevation

What can help identify an irregularly irregular rhythm if in doubt?

Absence of P waves

What is the appearance of atrial flutter?

Saw tooth appearance, multiple P waves, regular rhythm

What supplies the inferior aspect of most hearts?

Right Coronary Artery | 20%/left dominant hearts can be supplied by circumflex

What is it called when a QRS occurs earlier than expected suddenly?

``` Ventricular Ectopic (Waves?) (impulses travel through different pathways) ```

What is a left infero-lateral STEMI possibly caused by?

Circumflex Artery Stenosis (likely left-dominant patient)

What condition has saw tooths, or multiple P waves and regular rhythm?

Atrial Flutter

What does ST depression only in leads V2 and V3 suggest?

Reciprocal changes i.e. reciprocal ST elevation in the opposite direction to V2 and V3: the posterior heart. Thus, a posterior STEMI. If it was in other leads also, it would suggest ischaemia, NSTEMI.

Which arteries are occluded in a posterior STEMI?

Posterior Descending Artery from Right Coronary Artery (80% of the time, otherwise circumflex)

What is the MI triad?

ECG Changes Positive Troponin Chest pain You need 2/3 for it to be an MI

How do you investigate hypertrophy?

Look at the deepest and highest QRS complexes and find the height of those two together. If it is greater than a certain value, you have hypertrophy.

What can T-wave inversion signify?

Ischaemia, STEMI, NSTEMI

What is an ECG with regular rhythm, no P waves or T waves but several QRS complexes?

Ventricular Tachycardia

What is an ECG with regular rhythm, no P waves or T waves and several QRS complexes that gradually get larger in magnitude then smaller again and repeat this pattern?

Torsades (de Pointes) here the impulses from ventricles have a varying focus so imagine a straight line rotating around its centre, giving rise to a gradually increasing and decreasing magnitude.

What is an ECG with irregular rhythm, no P waves or T waves, several QRS complexes and varying magnitudes?

Ventricular Fibrillation | if rhythm is irregular --> fibrillation

What is an ECG with tented T-waves?

``` Hyperkalaemia can also get: Loss of P wave Bradycardia Broad QRS ```

What is a more accurate way of determining the Cardiac Axis?

Find the most equiphasic limb lead. The Cardiac Axis is running perpendicular to this lead. Out of the leads perpendicular to this lead (think which ones are 90deg away) the one which has a positive deflection is the direction of the cardiac axis. To increase accuracy, look again at the equiphasic lead. If it is truly equiphasic, you have your cardiac axis. If it is more positive, move the cardiac axis 15deg towards the equiphasic lead. If it is more negative, move the cardiac axis 15deg away from the equiphasic lead. Thus, you have your cardiac axis.

What is the cardiac axis?

The mean direction of the flow of electricity or wave of depolarisation through the heart.

What is often the earliest ECG change seen during myocardial infarction?

Tented T-waves in a few leads (i.e. tall peaked T-waves) If in all leads - Hyperkalaemia bc of potassium leaking through the damaged membrane over the infarcted area)

What view of the heart do leads V1 and V2 represent?

Septal The septum runs in between the right and left chambers of the heart.

If ST-elevation was noted in leads II, III and aVF what would it suggest?

inferior MI

What view of the heart do leads I, aVL, V5 and V6 represent?

Lateral

A patient is noted to have an abnormally shortened PR-interval on their ECG. Which of the following is the most likely cause? Left bundle branch block AV nodal fibrosis Right bundle branch block Wolf Parkinson White Syndrome

Wolf Parkinson White Syndrome A short PR-interval indicates abnormally short conduction time between the atria and ventricles. This is caused by the presence of an accessory pathway between the atria and ventricles. Wolf parkinson white syndrome is an example of this kind of disorder. In WPW the an accessory pathway known as "the bundle of kent" is present. Most individuals are asymptomatic however there is a risk of sudden death without treatment.

What is the most common cause of left axis deviation?

Defects of the conduction system. | Rarely is it left ventricular hypertrophy

What is the duration of a normal PR-interval and what is the significance?

In normal individuals the PR-interval is between 0.12-0.2 seconds. A PR interval longer than this can suggest the presence of heart block and a short PR-interval can suggest an accessory pathway between the atria and ventricles e.g. WPW syndrome

If a rhythm is described as sinus, what does this indicate?

If a rhythm is described as sinus it indicates that a P-wave precedes each QRS-complex. However a rhythm can still be irregular even if it's sinus.

What is the normal duration of a QRS complex?

In most healthy individuals you would expect QRS complexes to be around 0.12 seconds or slightly less. If a QRS complex lasts longer it is described as a "wide QRS" and can be a sign of inefficient conduction of the ventricles such as bundle branch block.

* Sinus rhythm, rate 77/min * Normal PR interval * Normal axis * Prominent and deep Q waves in leads II, III and VF, There are also small Q waves in leads V5–V6, * ST segments normal, with no elevation in the leads showing Q waves * Inverted T waves in leads II, III and VF

Clinical interpretation The Q waves in the inferior leads, together with inverted T waves, point to an old inferior myocardial infarction. What to do The patient seems to have had a myocardial infarction at some point in the past, and by implication his vague chest pain may be due to angina. Attention must be paid to risk factors (smoking, blood pressure, plasma cholesterol), and he probably needs long-term treatment with aspirin and a statin. An exercise test or a perfusion scan will be the best way of deciding whether he has coronary disease that merits angiography. Summary Old inferior myocardial infarction.