ECGs Flashcards
What is the normal cardiac axis?
-30 to 90 degrees,
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
Where is Right Axis deviation? (degrees)
between 90 and 180 degrees
What happens to the deflection in Lead I in Right ventricular hypertrophy?
Becomes more negative
What happens to the deflection in lead aVF and IIIin RVH?
More positive
When is Right Axis deviation a normal finding?
Very tall individuals (more vertical orientation of the heart)
Where is Left axis deviation in degrees?
between -30 and -90 degrees
When is left axis deviation considered significant?
Lead II negative as well as lead III (if just lead III insignificant)
Most common cause of LAD?
Conduction abnormalitisS
Which coronary artery correlates with V1-V4?
Left anterior descending
Which coronary artery correlates with the lateral leads?
Left circumflex, LAD diagnonal branch in some people
Which coronary artery correlates with inferior leads?
Right coronary artery or Left circumflex
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
Add these features to the basic ECG:
Atrial depolarization
Ventricular repolarization
Ventricular depolarization
Atrial repolarization
Atrial systole
Ventricular systole
Atrial diastole
Ventricular diastole
What does the P wave represent?
Atrial depolarisation
What does the PR interval represent?
Represents time taken for depolarisation go from atria to ventricles
QRS complex represents
The depolarisation of the ventricles
What does the ST segment represent?
Isoelectric line = time between de and repolarisation of ventricles - ventricular contraction
What does T wave represent?
Ventricular repolarisation
Draw out a labelled ECG
RR interval is
the peak of R waves = time between QRS complexes
QT interval represents
Time taken for ventricles to depolarise and repolarise
How many large squares are 1 second?
5
What is a small square on an ECG worth?
0.04s
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
AF
Absent P waves and irregulare rhythm suggest?
AF
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
