ECG Flashcards by sam Leckie

How many leads is a proper ECG ?

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What is each feature on an ECG ?

P wave = atrial contraction (depolarisation)
PR interval = AV nodal conduction
QRS = ventricular contraction (depolarisation)
T wave is ventricular repolarisation (repolarisation)
QT interval = total ventricular activity

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What is heart block ?

Delay/interruption in the electrical signal traveling from atria to ventricules
-e.g. prolonging PR interval

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What is on the x and y axis of an ECG recording ?

X-axis
-25mm/s
-small square = 0.04ms
-large square = 0.2ms

Y-axis
-10 mm = 1 mV

Can be adjusted

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How can heart rate be calculated from an ECG ?

Heart rate = 300 ÷ number of large squares between two R waves

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What is the hearts axis ?

Overall (average sum of) direction of ventricular depolarisation
-ECG changes dependeing on heart position/orientation

Hearts electrical axis

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What are the steps of a systematic ECG interpretation ?

Confirm details
Rate
Rhythm
Axis
QT interval
Qtc (corrected QT interval)
Old ECGs

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What is this

Normal ECG

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What do positive and negative chages mean on an ECG

Positive change = electricity flowing towards lead

Negative change = electricity flowing away from lead

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Which leads are limb and which are chest leads ?

Limb leads
-I, II, III, aVR, aVL, aVF
-Frontal plane

Chest leads
-V1–V6
-Horizontal plane

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Which are the inferior leads ?

leads II, III, and aVF
-Look at the heart from below
-Upright P waves in these leads indicate normal SA-to-AV depolarisation

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What does present P waves with abnormal relation to QRS complex indicate ?

Heart block
-Conduction to ventricles is delayed or absent

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What do absent P waves with an irregularly irregular ventricular rhythm indicate ?

Atrial fibrilation

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How can the axis of depolarisation be determined ?

I and aVF +ve = normal axis

I and aVF -ve = axis in the Northwest Territory

I -ve and aVF +ve = right axis deviation

I +ve and aVF -ve and lead II +ve = normal axis

lead II -ve = left axis deviation

0 degrees = left, +90 degrees = down

QRS complexes negative or positive

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What is a normal heart axis ?

-30° to +90°

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What is this ?

Left axis deviation
-Lead II is negative
-aVF is negative (electricty moves away from feet)

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What is this ?

Right axis deviation
-I -ve
-aVF +ve

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What is a normal PR interval ?

3-5 small squares (0.12 – 0.2ms)

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Give examples of P wave abnormalities

P pulmonale
P mitrale
Atrial ectopic

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What is P Pulmonale

Tall P wave (in limb leads, esp II)
-right atrial enlargement (hypertrophy or dilation)
-right-sided heart strain due to lung problems e.g. severe lung disease, pulm hypertension

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What is P Mitrale

Notched or double-peaked P wave; resembles M
-Left atrial enlargement (hypertrophy or dilation) e.g. due to mitral valve disease (stenosis/regurgitation) or hypertension
-Can lead to Afib

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What is atrial ectopic ?

P waves that originate outside the SA node
ECG can be:
-abnormal shape
-comes early
-different direction (e.g. inversion in II, III, aVF)

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Give examples of PR issues

Short PR interval E.g. Lown Ganong Levine syndrome
Heart block
Delta wave

Abnormalities tell us about conduction problems.

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What is Wolf-Parkinson-White syndrome ?

Causes delta wave
-Accessory pathway (Bundle of Kent) bypasses AV node
ECG:
-Short PR interval
-Slurred upstroke at start of QRS (delta wave)
-Wide QRS

Clinical consequence: reentrant tachyarrhythmias

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What is this ?

WPW -Short PR interval -Slurred upstroke at start of QRS (delta wave) -Wide QRS

What are the three main types of bradycardia ?

Sinus bradycardia (chill and youre really fit) Sick sinus syndrome (SA cooked) Heart block

What are the types of heart block ?

1st Degree 2nd Degree -Mobitz type 1 (Wenkebach) -Mobitz type 2 3rd Degree | 3rd is the worst

What is first degree heart block ?

A bradycardia; least bad type of heart block -Slow but existent conduction -Prolonged PR interval; av node really slow -If assymptomatic doesn’t need treaed

What is this ?

First degree heart block

What is mobitz type one bradycardia ?

Type of second degree heart block -a.k.a wenkebach -Usually benign/physiological cuased by high vagal tone e.g. young/fit people -Can occur at night when higher vagal tone Progressive lengthening of the PR interval which results in a P wave that fails to conduct a QRS; dropped beat

What is this ?

Mobitz type one Progressive lengthening of the PR interval which results in a P wave that fails to conduct a QRS; dropped beat

What is mobitz type 2 bradycardia ?

Type of second degree heart block -Each P wave associated with a QRS complex until one is not -Constant PR interval; may be no pattern/ratios -Usually caused by conduction system failure, especially at the His-Purkinje system -Often progresses to 3rd degree AV block

What is this ?

Mobitz type 2 -Each P wave associated with a QRS complex until one is not -Constant PR interval; may be no pattern/ratios

What is 3rd degree heart block ?

Complete heart block -No asssociation between P and QRS. -QRS still exists because ventricular contractions can occur without SA node relying on ventricular backup mechanism -Get this guy a pacemaker rn

What is this ?

3rd degree heart block -No association between P and QRS

How can tachycardia be identified from an ECG ?

No obvious P waves -may be hidden in QRS or T waves

What are the two main divisions of tachycardia ?

Broad and Narrow QRS

What are the narrow complex tachycardias ?

SVTs usually benign esp in young people but uncomfortable -If youre in SVT for a while and go back to sinus you get a big diuresis; histroy | WPW causes AVRT

What are the broad complex tachycardias ?

What is the difference between broad and narrow complex tachycardias ?

Narrow -Ventricles activated normally; rhythm is supraventricular Broad -Ventricular activation is abnormal or slow -Could be ventricular in origin

What is this ?

Mono-morphic VT -Broad regular QRS -Spooky -No P wave

What is this ?

Poly-morphic VT -Broad regular QRS -Spooky -e.g. tdp (as shown)

What is a ling QTc linked to ?

Sudden death

What is this ?

AF with LBBB -No P waves -Broad, irregularly irregular QRS rhythm

What is this ?

AF -No P waves -Narrow, irregularly irregular QRS rhythm -Top bit beats rellay fast and only some get conducted down from av node

What is this ?

Narrow complex SVT -Reguklar

What is this ?

Atrial flutter -Has a narrow regular QRS -Type of SVT

What can cause a broad QRS complex ?

Broad QRS = 3 small squares or .12ms -Ectopic ventricular beats (any beat that starts in the ventricles spreads slowly) -Bundle branch block -VT -Pacemakers (implant)

How does LVH affect QRS complex

Very tall QRS complexes; especially in left-sided leads QRS duration is often normal, but the voltage is increased

What is this ?

Ventricular ectopic -Broad, bizarre QRS complex not preceded by a P wave, often followed by a compensatory pause -May be asymptomatic or cause palpitations.

What is this ?

LBBB -Broad QRS -W notch in V1 (mostly negative), M notch in V6 (mosty positive) (Left ventricle is activated late via slower cell-to-cell conduction from the right ventricle) | Mostly positive = majority of complex above line ?

What is this ?

RBBB -Broad QRS -M notch in V1 (mostly positive), terminal (S) portion widened/slurred in V6 (mostly positive) | Mostly positive = majority of complex above line ?

What is this ?

A pacemaker -Thin vertical pacing spikes just before many of the QRS complexes -Broad QRSs Pacemaker on right has LBBB appearance and vice versa

What is this ?

Left ventricular hypertrophy -Tall R waves in left precordial leads (V5 and V6) and lead I -Deep S waves in right precordial leads (V1 and V2)

What does a wider and deeper Q wave indicate ?

Part of the ventricle is electrically silent due to infarction

What do T wave changes suggest ?

T wave changes = myocardial stress or ischaemia

What does QTc prolongation bring with it >

Risk of torsades de pointes Causes: drugs, electrolyte abnormalities (↓K, ↓Mg, ↓Ca), ischaemia 👉 QTc = ventricular repolarisation duration & arrhythmia ris

What causes QTc shortening ?

Hypercalcaemia (rare but classic)

What is this ?

Inferior MI -ST elevation in II, III and aVF -Reciprocal changes in I and aVL | RCA block ## Footnote AVf ST elevtaion means inferior

What is this ?

Anterior MI -ST-elevation in leads V1-V6, I and aVL. -Maximum elevation in V3, maximal depression in III -later: Pathological Q-wave in the precordial leads V2 to V4-V5.

What is this ?

Lateral MI -ST elevation in I, aVL, V5, and V6, -often with reciprocal ST depression in III and aVF

What is this ?

Posterior MI -ST depression V1-V3 -Tall R waves -Upright T waves in V1–V3 -ST elevation in posterior leads V7–V9. ## Footnote often missed as doesnt produce classic ST elevation on the standard 12-lead ECG Instead, you see reciprocal (mirror-image) changes in the anterior leads.

What are common causes of T wave changes ?

Ischaemia LVH with strain pattern Hyperkalaemia Digoxin effects

How does LVH affect the T wave ?

Chronic -Down-sloping ST depression -Asymmetrical T-wave inversion Seen in left-sided leads (I, aVL, V5–V6)

What is this ?

NSTEMI/Ischaemia -ST depression (horizontal/down-sloping) in two contiguous leads -Symmetrical, deep T-wave inversion in contiguous leads -Changes over time -Early ischaemia; tall, broad T waves e.g. before ST Changes seen in leads of ischaemic tissue ## Footnote no ST elevation or New pathological Q waves as this is of STEMI

What is this ?

Hyperkalaemia Progressive changes, starting with; -Tall, peaked T waves, then -Prolonged PR interval -Flattened P waves -Widening QRS complex, -Sine wave pattern

What is this ?

Digoxin reverse tick -Scooped out depression in ST, often with T waves rising above baseline (normal with use) With toxicity -Reverse tick becomes more pronounced -T wave changes; e.g. flat/inverted -Shortened PR