ECGs-how-to Flashcards
What directions are lead 1, 2, 3, RA, AVR, aVF, AVL and v1-6?
What parts of the heart/vessels do the different ecg leads correspond with?
- 1, avl, +/- V5-6 = lateral heart = left circumflex
- V1-4 = anterior = LAD
- 2, AVF, 3 = inferior = right coronary artery
What is the systematic process for looking at ECGs?
- Patient details/calibration
- Rate
- Rhythm
- Axis
- P wave
- PR interval
- QRS complexes
- ST segment
- T waves
- QT interval
What should be looked for regarding patient details and calibration?
- patient details
- history
Calibration: 10mV and 25 mm/s
What should be looked at regarding rate on ecg?
- calculate qrs peaks x6 for rate
- >100 = tachycardic
- <60 = bradycardic
What should be looked at regarding rhythm on ecg?
- are there P waves before QRS?
- is P-R constant?
if yes then is sinus!
What would you see for rhythm regarding AF?
- there are no P waves
- it is Irregularly irregular
- can use paper to check if regularly irregular
can see F waves - A pattern of irregular undulations of the base line in an electrocardiogram that is indicative of atrial fibrillation.
Tx: cause - structrue or systemic (hyperthyroid); control - electric DC; anticoagulation - chadvasc >2 = be on warfarin or doac e.g. rivoraoxaban
What would be seen regarding atrial flutter?
- these are regular (usually, can be other)
- e.g. regularly irreg
- but faster than usual e.g. more often than ventrivles e.g. for 4 atrial beats:1 ventricular beats
- but sawtooth
- flutter waves ~200-300, beat regularly but
What is the difference between atrial fibrillation and atrial flutter?
Atrial flutter and atrial fibrillation are both abnormal heart rhythms. …
In atrial fibrillation, the atria beat irregularly.
In atrial flutter, the atria beat regularly, but faster than usual and more often than the ventricles, so you may have four atrialbeats to every one ventricular beat.
What is sick sinus arrythmia?
- pathological sinus arrthymia
What is a normal sinus arrhythmia?
How can you tell axis deviation?
- left axis deviation
- legs leaving
- right axis deviation
- reaching/legs together
What can cause left axis deviaton?
left axis deviation can be caused by
- LV hypertrophy
slots of deviation to move axis
RV infarct will also pull axis to LHS (like releasing part of elastic band)
What causes right axis deviation?
- left ventricle infarct
- cor pulmonale / right ventricular hypertrophy
How do you examine P waves on an ecg?
- look at lead II
- shows p waves best
- height <2.5ss
- Width <3 ss
What could tall P waves indicate?
- e.g. height > 2.5 ss
Tall indicated RA enlargement/hypertrophy
the commonest RA hypertrophy cause is COPD
= tf called p.pulmonale
What do bifid p waves: broad p waves indicate?
- Left atrial enlargement
- found from rheumatic fever affecting the mitral valve –>
- LA enlargement is an early-mod sign of mitral stenosis
- = p. mitrale
- mitral stenosis can flip into AF - so AF would be a late sign while LA enlargement is early/mod sign of mitral stenosis
Why is ecg calibration important?
What does each small square on ecg represent?
What does a large square on ecg represent?
How do you identify RBBB vs LBBB?
looking at broad QRS >3ss and their QRS height in…
… V1 and V6
if V1 is mostly positive = RIGHT bbb
- which side is more broad? MARROW
- M in V1, V2 (RHS)and W in V5,6 (LHS)
if v1 is neg = LEFT
- WILLIAM
- W in V1,2 (RHS) and M in V5,6 (LHS)
NB: the criteria for MI is new onset left BBB
- LBBB is never normal and is usually assoc. w/ischaemic HD or structural HD
What does a tall QRS indicate?
What does a broad QRS indicate?
- left ventricular hypertrophy
- (>3 squares/>3mV)
- LVH with strain is not MI is due to LVH (e.g. ic blood presure)
- T wave inversion left ventricle are thick so outside in needs to treavel in muscle ischaemia
- look at S wave in V1, V2 to tallest R wave in V5,6 if >3s
- Broad QRS = ventricular pathway broken or nor being used at all e.g LBBB QRS= left going down in V1= WILLIAM
- Broad QRS = not likely from AV node e.g. Ectopic and alternative pathway
What are pathological Q waves?
Q waves indicate an old MI or ongoing MI - >2 small squares tall
[wide= > 40 milliseconds (one small box) or size= > 25% of the QRS complex amplitude.]
you will see the q waves in concordant leads e.g. LAD/anterior V1-V4; lef circumflex/lateral 1, AVL, V5,6; RCA/inferior 2,3,AVF
What are the signs of MI?
- Pathological q waves
- posterior MI (and chest pain): tall r waves in V1 and V2; will see ST depression in posterior stemi
- remember the RCA also does a bit posterior so look on leads to see
- St elevation in STEMI
- and ST segment depression in NSTEMI - inverted/anormal T waves
- (depression = ischaemia, reversible tissue dysfunction)
- remember T waves are always inverted in AVR and V1 - castle look on ecg for actual t wave inversion
- Pericarditis = all st elevation (due to relative PR depression - looks like diffuse ST seg elevation)
- Hx: leaning forward, pleuritic, (pmhx of resp infection)
- Tx pericarditis: colcine and nsaids ->> conservative therapy until resolves on its own
- Hx: leaning forward, pleuritic, (pmhx of resp infection)
- T-wave changes including low-amplitude T wavesand abnormally inverted T waves may be the result of many cardiac conditions such as myocardial ischemia, myocarditis, mitral valve prolapse, or ventricular strain.
What should be considered regarding QT interval?
- in cardiology the Q-T interval should not be larger than 2 boxes wide
- if Q-T is abnormally short or long there is a risk of developing verious types of ventricular arrhythmias
- some QT prolongation can cause polmorphic ventricular tachycardia with a characteristic twist of the QRS complex around the isoelectric baseline - called Torsades de Pointed (TdP)
- this can be caused by anti histamines, anti psychotics, erythromycin
What should be considered regarding T waves on ECG?
- if there are tall/tented T waves = hyperkalaemia
- also signs of hyperkalaemia = low flat Ps, prolonged PR, broad, QRS, tall tented T waves
- Hx: could be crush injury that relases K+ from muscles
- If there are shortened flat = hypokalaemia/thyroid/hypothermia
What is the Sokolow-Lyon criteria?
- left ventricular hypertrophy criteria
- Largest S wave - V1 or V2
- Largest R wave - V5 or V6
- sum is greater than 35mm (7 large squares)
How can you tell an ectopic beat on ECG?
- will look completely different
