ECGs Flashcards
Give the diagnosis:
Sinus rhythm followed by no p wave before a normal QRS, or one immediately before or after the normal QRS; the next p wave is late, followed by sinus rhythm
Junctional (nodal) extrasystole
When do you see -ve or +ve deflections of the QRS?
-ve in I, and +ve in III is R axis deviation
predominantly -ve in II and III is L axis deviation
What sort of pathology does LBBB indicate?
Heart disease, ~ on the L side Aortic stenosis Ischaemic disease Hypertension Cardiomyopathy Acute MI if also chest pain
What do hyperacute T waves indicate?
MI
How can you identify atrial flutter on an ECG?
Look at leads II, aVR and aVF
Narrow complex tachycardia
P waves at >250 bpm, and multiple p waves per QRS
No flat baseline between p waves (sawtoothed appearance)
If the R-R interval is 5, what is the heart rate?
300/5 is 60
Give the diagnosis:
No p waves, only an irregular baseline
Normal shaped QRS complexes, very irregular rate (may be abnormal shape if also a BBB)
V1 may look a bit sawtoothed
Atrial fibrillation
Give the diagnosis: No relationship between p and QRS Different rates for p and QRS Abnormally shaped or broad QRS Slow QRS rate
3rd degree (complete) heart block
What does a thick base line on the ECG reading indicate?
Electrical interference eg. from electric lights or electric motors on beds/mattresses
What ECG changes are seen in digoxin Tx?
Downward sloping ST segment
Give the diagnosis:
Sinus rhythm followed by an abnormal, early p wave, normal but early QRS; the next p wave is late, followed by sinus rhythm
Atrial extrasystole
What ECG changes are seen in R and L atrial hypertrophy? Give 2 causes of each
Right:
Peaked p waves
Tricuspid valve stenosis
Pulmonary hypertension
Left:
Broad and bifid p waves (p mitrale)
~ due to mitral stenosis
Also can be due to mitral regurg
What does an RSR1 pattern indicate in V1?
RBBB
Normal if <120 ms (partial RBBB)
Give the diagnosis:
Delay after a beat, followed by an abnormal p wave and normal QRS. Returns to sinus arrhythmia
Atrial escape
Which direction is the depolarisation wrt the sizes of the R and S waves?
R>S (overall upward) means depolarisation is moving towards that lead.
S>R (overall downward) means it’s moving away.
R=S means the depolarisation wave is moving at right angles to the lead.
How do you determine a normal 11 o clock - 5 o clock axis?
They will be a predominantly upward deflection in leads I, II and III, with a greater deflection in II
What ECG changes are seen in PE?
Can have a normal ECG with sinus tachycardia
RBBB
Peaked p waves
Increased height of the QRS (>35 mm) in V1
Q wave in III but no aVF + R axis deviation
Dominant R waves in V1 (R>S)
Deep S wave in V6
Transition point shifted to V5 or V6 (clockwise rotation)
T waves inversion in III, V1, V2 and possibly V3 and V4
What ECG changes are seen in L anterior hemiblock?
Marked L axis deviation
Deep S waves in leads II and III, ~ with a slightly wide QRS complex
When are p waves broad and bifid (p mitrale)?
L atrial hypertrophy, which is ~ due to mitral stenosis, or sometimes mitral regurg
How do you work out the position of an MI?
Anterior: V3-4 (often V2 and V5)
Inferior: III and aVF
Lateral: I, aVL, V5-6
True posterior: dominant R waves in V1
Give the diagnosis:
Slow QRS rate
No p waves in junctional beats, but normal QRS
Nodal (junctional) escape
How do you determine R axis deviation. What sort of conditions is this associated with?
I has negative deflection.
III has increased positive deflection of the QRS.
Caused by R ventricular hypertrophy, which is associated with pulmonary conditions that put a strain on the R heart (eg. PE), as well as congenital heart disorders.
Can also be normal in tall, thin people
What are the causes of sinus arrhythmia?
Changes in heart rate associated with respiration - ~ seen in young ppl
When are QRS complexes narrow?
Supraventricular rhythms (sinus, atrial, nodal)
What can the rhythms arising in the atrial muscle, junctional (nodal) region or ventricular muscle be categorised as?
Bradycardic (slow and sustained)
Extrasystoles (occur as early single beats)
Tachycardic (fast and sustained)
Fibrillation (totally disorganised activation of atria / ventricles)
What does a tall R wave to >25 mm indicate?
L ventricular hypertrophy if in V5 or V6
R ventricular hypertrophy or normal if in V1
What effect might the pt moving eg. from Parkinson’s or shivering, have on the ECG?
A jerky appearance
What are the ECG signs of L ventricular hypertrophy?
Deep S in V1/2
Tall R (>25 mm) in V5/6
Inverted T waves in I, II, aVL and V5/6, and sometimes V4
L axis deviation
What does a short PR interval indicate?
Wolff-Parkinson-White
How can you identify atrial fibrillation on an ECG?
No p waves, only an irregular baseline
Normal shaped QRS complexes, very irregular rate (QRS complexes may be an abnormal shape if also a bundle branch block)
V1 may look a bit like atrial flutter (sawtooth)
How do you work out the position of the ventricular septum? What’s the clinical relevance of this?
The QRS goes from predominantly downward in V1 to predominantly upward in V6. The transition point where the R and S waves are equal indicates the position of the ventricular septum.
The more the right ventricle is enlarged, the more this transition point moves from V3/V4 to V4/V5 or V5/V6.
When might the ST segment disappear?
High K+
What are the values for one small square laterally, and one large square laterally and vertically?
Laterally one small square is 0.04s or 40ms
Laterally one large square is 0.2s or 200ms
Vertically one large square is 0.5mV (0.5cm)
When are p waves peaked?
R atrial hypertrophy (eg. from tricuspid valve stenosis or pulmonary hypertension)
R ventricular hypertrophy
PE
Where do you place the leads on the body for the ECG?
LA = L arm RA = R arm LL = L leg RL = R leg
Find the 2nd intercostal space by finding the space below the sternal angle
V1 = R of sternum at 4th intercostal space
V2 = L of sternum at 4th ICS
V3 = Halfway between V2 and V4
V4 = Midclavicular line 5th ICS
V5 = Horizontally inline with V4, anterior axillary line (fold of skin that marks the front of the armpit)
V6 = Horizontally inline with V4/V5, midaxillary line
Give the diagnosis:
After sinus beats, there’s a pause followed by a single wide, abnormal QRS with an abnormal T wave. Sinus rhythm then continues.
Ventricular escape
How can you identify ventricular fibrillation on an ECG?
No QRS complexes
The ECG is totally disorganised
LOC in pt
If the R-R interval is 2, what is the heart rate?
300/2 is 150
How can you identify junctional (nodal) tachycardia on an ECG?
No p waves, or very close to the QRS complexes
Normal QRS complexes (might be narrow) (abnormal if also a bundle branch block or ventricular tachycardia)
Fast QRS rate (150-180/min)
If the R-R interval is 6, what is the heart rate?
300/6 is 50
What do the intervals and segments of the ECG represent, and what are their normal time lengths?
PR interval is the time taken for excitation to spread from the SA node, through the atrial muscle and AV node, down the bundle of His and into the ventricular muscle. Normally it’s 3-5 small squares (120-200ms).
The duration of the QRS shows how long excitation takes to spread through the ventricles (depolarisation). Normally it’s <3 small squares (120ms).
The ST segment is the time taken for the ventricles to contract.
QT interval is usually <11 small squares (450ms).
What are the underlying causes of 3rd degree (complete) heart block?
An acute phenomenon in pts with an MI (when it’s ~ transient)
A chronic state, ~ due to fibrosis around the bundle of His
Block of both bundle branches
How can you identify extrasystoles on an ECG?
Sinus rhythm followed by an:
Atrial: abnormal, early p wave; normal but early QRS; the next p wave is late, followed by sinus rhythm
Junctional (nodal): no p wave before normal QRS, or one immediately before or after the normal QRS; the next p wave is late, followed by sinus rhythm
Ventricular: no p wave, then an abnormal, wide, early QRS; inverted T wave; the next p wave is on time, followed by sinus rhythm
What is the normal axis range in degrees?
-30° to +90°
What ECG changes are seen in R ventricular hypertrophy?
R axis deviation
Sometimes RBBB
Peaked p waves
Normally S>R in V1 (and V2), but in R ventricular hypertrophy there’s a tall R wave (>25 mm) so that R>S (but this may be normal)
Deep S wave in V6
T waves inversion in V1, V2 and possibly V3 and V4
What does ST elevation indicate?
Acute MI or pericarditis
What do pathological Q waves indicate?
Septal Q waves (>1 mm (1 small square) and 2 mm deep) in MI, or normal in I, II, aVL, V5, V6 and possibly III
in III but not aVF, plus R axis deviation, indicates PE
What ECG changes are seen in low K+ and high K+?
Low: T waves are flattened and prolonged, and then there’s a hump at the end (u wave)
High: Peaked T waves; ST segment disappears
What ECG changes are seen in high Ca+?
Shortened QT interval
Give the diagnosis:
progressive lengthening of PR intervals, then a p not followed by a QRS, then returns to beginning of cycle
2nd degree heart block: Wenckebach
What may cause a very jerky appearance to the ECG reading?
If the pt isn’t still eg. shivering or moving (eg. Parkinson’s)
Heart block refers to interference with which process? Where is this on the ECG reading?
What are the differences between the pathology of the different heart blocks? How do each represent on ECG?
The conduction process of depolarisation from the SA node, through the atria, the AV node, the His bundle and then it’s branches, to the ventricular muscle.
This is represented by the PR interval.
1st degree:
Delay somewhere along the conduction pathway.
1 p wave per QRS. PR >200 ms.
2nd degree:
Intermittent failure of the excitation to pass through the AV node or bundle of His.
Mobitz type 2: Mostly constant PR intervals; an occasional p not followed by a QRS.
Wenckebach: Progressive lengthening of PR interval, then a p not followed by a QRS, then returns to beginning of cycle.
2:1: Normal, constant PR interval; 2 p’s per QRS (also can have eg. 3:1) (note p waves can be shown as a distortion of T waves)
3rd degree (complete heart block): Atrial contraction is normal, but no beats are conducted to the ventricles, so the ventricles are excited by a slow 'escape mechanism' No relationship between p and QRS; different rates for p and QRS; abnormally shaped or broad QRS; slow QRS rate
Give the diagnosis: Leads II, aVR and aVF Narrow complex tachycardia P waves >250 bpm Multiple p waves per QRS No flat baseline between p waves (sawtoothed)
Atrial flutter
When are QRS complexes wider then 120 ms (3 small squares)?
BBB
Wolff-Parkinson-White
When depolarization is initiated in the ventricular muscle, causing ventricular escape beats, extrasystoles or ventricular tachycardia
What parts of the heart do the different leads look at?
I, II and aVL look at the L lateral surface of the heart.
III and aVF look at the inferior surface.
aVR looks at the R atrium.
V1 and V2 look at the R ventricle.
V3 and V4 look at the septum between the ventricles and the anterior wall of the L ventricle.
V5 and V6 look at the anterior and lateral walls of the L ventricle.
What are the underlying causes of 1st +/ 2nd degree heart block?
Can be seen in normal people Acute MI Coronary artery or heart disease Acute rheumatic carditis Digoxin toxicity Electrolyte abnormalities
What are u waves and what do they indicate?
A hump at the end of a T wave
If preceded by a flattened and prolonged T wave, this indicates low K+
What is the standard rate for an ECG machine to run at?
25mm/s
Which direction is the septum normally depolarised?
When might it be depolarised in another direction?
Left to right
In LBBB the septum is depolarised from R to L
Give the diagnosis:
No QRS complexes
Completely disorganised ECG
Ventricular fibrillation
How can you identify atrial tachycardia on an ECG?
Tachycardia >150 bpm
Normal QRS complexes; regular regularity
P waves may be superimposed on the T waves preceding them, hence a short PR interval; more p wave than QRS complexes
Give the diagnosis:
No p waves, or very close to the QRS complexes
Normal QRS complexes (might be narrow) (abnormal if also BBB or ventricular tachycardia)
Fast QRS rate
Junctional (nodal) tachycardia
What does a shortened QT interval indicate?
High Ca+
What do deep S waves indicate?
In V6: PE Chronic lung disease R ventricular hypertrophy RBBB (deep and wide)
V1 or V2:
L ventricular hypertrophy
II and III:
L anterior hemiblock
LBBB
If the R-R interval is 4, what is the heart rate?
300/4 is 75
What do the different waves of the ECG represent?
P is contraction of the atria
QRS is the depolarisation of the ventricles
T is repolarisation of the ventricles
What are the causes of sinus bradycardia?
Athletic training Fainting / vasovagal attacks Hypothermia Hypothyroidism Immediately after an MI
If there’s a bundle branch block, what implications does this have for looking at the rest of the ECG?
LBBB prevents any further interpretation
RBBB can make interpretation difficult
What sort of pathology does RBBB indicate?
Normal heart
Problems in the R side of the heart
Atrial septal defect or other congenital disease
PE
With L axis deviation: severe conducting tissue disease
What are QRS complexes broad with a notched top?
In V6 in LBBB
What are the signs of cardiomyopathy on ECG?
Non-specific ST changes
Conduction defects
Arrhythmias
Hypertrophic:
L axis deviation
L ventricular hypertrophy
Q waves in inferior and lateral leads
Restrictive:
Low voltage complexes
What ECG changes are seen during exercise?
Tachycardia
ST segment depression (esp. if there’s angina)
Explain the changes on an ECG seen in Wolff-Parkinson-White syndrome
In addition to the bundle of His, some ppl have an extra or accessory conducting bundle between the atria and ventricles (~ on the L side). This has no AV node to delay conduction, so depolarisation reaches the ventricle early, leading to pre-excitation.
Short PR interval
Early slurred upstroke in QRS complex (delta wave); the rest of the QRS is normal
Sinus rhythm
A paroxysmal tachycardia can occur, causing a re-entry circuit. This shows as a tachycardia with no p waves
Give the diagnosis: >150bpm Normal QRS complexes, regular regularity P waves may be superimposed on the t waves preceding them More p waves than QRS complexes
Atrial tachycardia
If the R-R interval is 3, what is the heart rate?
300/3 is 100
Give the diagnosis:
Normal sinus rhythm followed by an abnormal, ~ wide QRS and inverted T wave; the next p wave is on time, followed by sinus rhythm
Ventricular extrasystole
Give the diagnosis:
mostly constant PR intervals; occasional p not followed by QRS
2nd degree heart block: Mobitz type 2
What are the causes of sinus tachycardia?
Exercise Fear Pain Haemorrhage Thyrotoxicosis Obesity Pregnancy Anaemia CO2 retention
How can cardiac rhythms be classified wrt their origin? What are the ECG changes seen for each and why?
Supraventricular
Sinus, atrial, nodal (junctional)
Narrow or normal QRS (depolarisation still passes through His bundle and branches)
Will be wide QRS if also a BBB or Wolff-Parkinson-White
Normal T waves
Ventricular:
Wide, abnormal QRS (depolarisation spreads more slowly through Purkinje fibres)
Abnormal T wave (abnormal repolarisation)
What effect might electrical interference eg. from electric lights of electric motors on beds/mattresses have on the ECG?
Thick base line
What ECG changes are seen in pericarditis?
Elevated ST segment
What does T wave inversion indicate?
Normal in V1, aVR, sometimes III and V2, and V3 and V4 in some black ppl
In V1, V2, and possibly V3-4 indicates R ventricular hypertrophy, PE, RBBB
In aVL, V5 and V6 indicates LBBB or L ventricular hypertrophy
Can also indicate ischaemia, digoxin Tx, MI or Wolff-Parkinson-White
What is the order for reporting an ECG?
Rhythm Abnormalities of the p wave (tall/broad) Cardiac axis QRS duration or abnormal Q waves Elevated or depressed ST segment T waves normal or inverted
What does a shifted transition point indicate?
Shifted to V5 or V6 in PE or chronic lung disease (clockwise rotation)
How do you determine L axis deviation. What sort of conditions is this associated with?
III develops predominantly negative deflection in the QRS.
It only becomes significant once II also becomes predominantly negative as well.
Due to L ventricular hypertrophy / a conduction defect.
If the R-R interval is 1, what is the heart rate?
300/1 is 300
What degree do each of the leads look at the heart from?
I is 0° II is +60° aVF +90° III +120° aVR -150° aVL -30°
Describe the ECG changes in an MI
Over a period of 24-48h:
In a STEMI: first you get an elevated ST segment (1 mm in limb leads, >2 mm in chest leads); Then pathological Q waves appear (>1 mm (1 small square) wide and 2 mm deep); Then the ST segment returns to the baseline; Then T waves become inverted (often permanently).
Also you can get hyperacute T waves
In an NSTEMI: may show T wave inversion or ST depression
In an MI of the posterior of the L ventricle, you get an increased QRS height (>35 mm) in V1
Give the diagnosis:
Wide, abnormal QRS complexes in all 12 leads
Difficult to identify p or t waves
Ventricular tachycardia
Are the deflections in II and aVR mainly positive or negative and why?
Positive in II and negative in aVR.
These leads look at the heart from opposite directions.
What do peaked T waves indicate?
High K+
How can you identify ventricular tachycardia on an ECG?
Wide, abnormal QRS complexes in all 12 leads
Rate > 160/min
Difficult to identify P or T waves
What is a delta wave and when is it seen?
An early slurred upstroke of a QRS
Wolff-Parkinson-White
What does ST depression indicate?
May be seen during exercise (esp. if there’s angina), or in an NSTEMI
Horizontal depression with an upright T wave is ~ ischaemia instead of infarction
Downward-sloping in digoxin Tx
What does increased height of the QRS to >35 mm indicate?
PE or MI of the posterior of the L ventricle in V1
Give the diagnosis:
normal, constant PR interval; 2 p’s per QRS; p waves can be shown as a distortion of T waves
A 2:1 2nd degree heart block
What’s the effect of a bundle branch block on an ECG and why?
Widened QRS (>120ms or 3 small squares) b/c there’s a delay in the depolarisation of the ventricular muscle.
RBBB:
RSR1 pattern in V1 (up, down, up the same amount as the first up).
Inverted T waves in V1 and sometimes V2 and V3.
Deep, wide S waves in V6.
Can be normal in healthy pts if there’s a normal QRS.
LBBB:
Broad QRS in V6 (and sometimes V4-5) with a notched top (small up, small down, big up)
Can have T wave inversion in some or all of I, aVL, V5, V6, and sometimes V4.
Deep S waves in II, III
No septal Q waves
