ECGs Flashcards by Hannah Nolan

What is the normal cardiac axis?

-30 to 90 degrees,

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Why is there positive deflection towards Leads I, II and III?

Because in a healthy person the overall direction of electricity is in this direction

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Where is Right Axis deviation? (degrees)

between 90 and 180 degrees

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What happens to the deflection in Lead I in Right ventricular hypertrophy?

Becomes more negative

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What happens to the deflection in lead aVF and IIIin RVH?

More positive

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When is Right Axis deviation a normal finding?

Very tall individuals (more vertical orientation of the heart)

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Where is Left axis deviation in degrees?

between -30 and -90 degrees

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When is left axis deviation considered significant?

Lead II negative as well as lead III (if just lead III insignificant)

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Most common cause of LAD?

Conduction abnormalitisS

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Which coronary artery correlates with V1-V4?

Left anterior descending

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Which coronary artery correlates with the lateral leads?

Left circumflex, LAD diagnonal branch in some people

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Which coronary artery correlates with inferior leads?

Right coronary artery or Left circumflex

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Draw a basic ECG waveform labelling:QRS complex
R wave
P wave
Q wave
ST segment
T wave
S wave
QT interval
Isoelectric line

check

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Add these features to the basic ECG:

Atrial depolarization
Ventricular repolarization
Ventricular depolarization
Atrial repolarization
Atrial systole
Ventricular systole
Atrial diastole
Ventricular diastole

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What does the P wave represent?

Atrial depolarisation

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What does the PR interval represent?

Represents time taken for depolarisation go from atria to ventricles

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QRS complex represents

The depolarisation of the ventricles

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What does the ST segment represent?

Isoelectric line = time between de and repolarisation of ventricles - ventricular contraction

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What does T wave represent?

Ventricular repolarisation

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Draw out a labelled ECG

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RR interval is

the peak of R waves = time between QRS complexes

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QT interval represents

Time taken for ventricles to depolarise and repolarise

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How many large squares are 1 second?

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What is a small square on an ECG worth?

0.04s

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Draw the postiions of chest leads

What leads are anterior view?

V3+ V4

What leads are lateral?

Lead I, aVL, V5, V6

Septal leads

V1 + V2

Inferior leads

Lead II, Lead III, aVF

What happends to the R wave vs the S wave when depolarisation is moving towards the lead?

R wave is greater than S

When S is bigger than R wave where is depolarisation?

Away from the lead

Route of electrical activity in healthy individual?

SA node -> AV node -> Bundle of His -> Purkinje fibres -> ventricular contraction

Draw the cardiac axis?

Where does the cardiac axis lie in healthy individuals?

-30 to +90 degrees - positive deflection in Leads aVL, I II, aVF

What are the parameters for Right axis deviation?

90 and 180 degrees

Most common cause of RAD

Right ventricular hypertrophy - more cells = stronger signal

What conditions is right axis deviation ass with + when is it normal

Pulm HPTN normal in v tall individuals

Parameters for LAD degrees

-30 to -90 degrees

What happens to lead III in LAD + when significant

Lead III = negative Significant = Lead II also negative

What causes LAD

Conduction abnormalities LVH

How to calculate heart rate with a regular rhythm

300/number of squares within one RR interval

Sawtooth baseline suggests

Absent P waves and irregulare rhythm suggest?

Normal PR interval

120-200 ms (3-5 small squares)

What does a prolonged PR interval signal?

>0.2s = AV block

First degree heart block sign on ECG

Fixed prolonged PR interval >200ms

2nd degree mobitz I heart block features on ECG

Progressive prolongation PR interval QRS complex completely dropped then resumes and repeats pattern

2nd degree heart block mobitz II on ECG

Consistent PR interval duration intermittnetly dropped QRS complexes - repeating cycle

What is third degree heart block

No communciation between atria and ventricles

Third degree heart block on ECG

Presence of P waves and QRS complexes with no association to each other - atria and ventricles functioning independently

Where does narrow QRS complex escape rhythms originate

Above bifurcation of bundle of His = <0.12s

Character of tousseads de points

Twisting Ventricular tachycardia

What is the diagnosis of ST elevation in Lead III?

Inferior STEMI

How can you discern where the MI has taken place?

Wherever there are ST elevations - which lead compares to which area of the heart

If there was ST elevation in V3 - V6, what MI would it be?

ANTERIOR lateral STEMI

If there is ST elevation in I + AVL + V5 + V6 where is the MI?

Lateral - LCx or diagonal LAD branch

What MI occurs when LAD obstructed in patietns where supplies the majority of the heart?

Intero-inferolateral (confirm by angiogram)

What imbalance can cause hyperacute T waves?

Hyperkalemia

Which leads can ST depression be reciprocal in?

VI, V2

What three types of ST depression are there?

Upsloping, downsloping or horizontal

When do horizontal or downsloping ST depression indicate MI?

>0.5mm at J point in more than 2 contigpious leads

What does an ST depression above 1 vs 2 mm indicate?

Above 1 - needs to be more specific 2 - in 3 or more leads, high probablility NSTEMI

What defines a VT on ECG and when is it sustained

Broad complex tachycardia 3 or more Ventricular atopoic beats at a rate of >120 bpm If >30 s = sustained

Which VT is ass with MI and is more common?

Monomorphic

What does polymorphic VT ook like on an ECG

QRS 200bpm +, changes amplitude and axis, appear twist around baseline

Casues of VT

Channelopathies (Na+ and K+) WPW QT prolongation Electrolyte disturbances Hyporthermia Structural HD

What to look for in V1 and V6 in RBBB

V1 = M V6 = W MaRroW

What to look for in LBBB

V1 - W V6 - M WiLliaM

Features of RBBB om ECG

QRS duration > 120ms Dominant S wave in V1 Broad monophasic R wave in lateral leads (I, aVL, V5-6) Absence of Q waves in lateral leads Prolonged R wave peak time > 60ms in leads V5-6

VF on ECG

Chaotic irregular deflections of varying amplitude No identifiable P waves, QRS complexes, or T waves Rate 150 to 500 per minute Amplitude decreases with duration (coarse VF –> fine VF)

What are examples of structural heart disase that cause VT?

LV dysfunction CAD MI HOCM

Causes of RBBB

Ischaemic heart disease Structural HD eg Right ventricular hypertrophy / cor pulmonale, Rheumatic heart disease, Congenital heart disease (e.g. atrial septal defect), Myocarditis, Cardiomyopathy Pulmonary embolus Lenègre-Lev disease: primary degenerative disease (fibrosis) of the conducting system Aortic stenosis Anterior MI Hyperkalaemia (resolves with treatment) Digoxin toxicity

Bifascicular + first degree AV block on ECG

RBBB LAD First degree AV block

True trifascicular block 2 presentaions on ECG

3rd degree AV block + RBBB + either LAFB or LPFB

What is true fascicular block

Conudction delay in all three fascilcles below the AV node RBBB, LAFB,.LPFB

What cna be seen on ECG of an NSTEMI?

Nothing or T wave inversion, ST segment depression

What is S1Q3T3 ECG pattern?

S wave in lead I (indicating a rightward shift of QRS axis) with Q wave and T inversion in lead III.

When is the PR interval lengthened?

1st degree HB Hyperkalemia

Mobitz 1 vs 2

1 - prolonging PR intervals then drop QRS and return to start 2 - PR intervals are same length, occasionally drop QRS

3rd degree HB

No ass p wave and QRS

What extra waves are present in hypokalemia

U waves

ECG changes for thrombolysis or PCI

anterior leads (V1-V6) OR ST elevation of greater than 1mm (1 small square) in greater than 2 consecutive inferior leads (II, III, avF, avL) OR New Left bundle branch block

LVH vs RVH on ECG

LVH Tall R waves >25mm, ST depression, T wave flattening in L ventricular leads V5, V6 Deep S waves >30mm in R v leads - V1+V2 RVH Tall R waves in RV leads V1+2

When do braod QRS occur

Delayed conduction through ventricles eg R or LBBB

What can ST elevation signify

=>1mm STEMI or pericarditis

QT interval normal time

<440ms in females <460ms in males

Causes of prolonged QT interval

Hypokalaemia Hypocalcemia Hypomagnesaemia Meds

What arrhythmia is increased risk with QTc syndrome

Torsades de pointes VT and sudden death

What does doppler scanning assess

Valve lsions severeity Estimate CO Assess coronary blood flow

When is stress ECHO used

Increase oxygen demand of mycoardium detect CA disease Risk post MI and perioperatively Can use dobutamine if cant exercise

Investigation of choice for CAD

CTCA - coronary angiogram