CVD - Basic ECG Flashcards
What are some additional lead placements in ECG? What are the indications?
- Right ventricular leads V4R-V6R: if suspecting right ventricular infarction
- Posterior leads V7-9: if suspecting posterior ischaemia
What is a systemic ECG interpretation (order of things)?
- Rhythm and rate
- Cardiac axis
- PR interval
- QRS complexes
- ST segments and T waves
- QT interval
What is the ratio of p waves to QRS in normal sinus rhythm?
1:1 ratio
How do Premature atrial complexes (“atrial ectopics” look like on ECG?
early, narrow complex QRS followed by compensatory pause
How do Premature ventricular complexes (“ventricular ectopics”) look like on ECG?
early, broad complex QRS
How does Atrial fibrillation look like on ECG?
absence of p waves, irregularly irregular rhythm
Need to comment on ventricular response rate
> 100 – “rapid ventricular response rate”
How does Atrial flutter look like on ECG?
“saw tooth” appearance of p waves due to large re-entrant pathway in atrium, REGULAR 300bpm
How do you pick left axis/right axis deviation on ECG?
Look at Lead I & II/aVF.
- Normal axis: positive, positive
- Left axis dev: positive, negative (Ladies Adore Diamonds; in diamond shape)
- Right axis dev: negative, positive (Rover Adores Digging; in the shape of dug bone edges. opposite of diamonds)
When do you get left axis deviation?
- Left anterior hemiblock
- Ischaemic heart disease
- Cardiomyopathy
- Hypertension
- Wolff-Parkinson-White syndrome - right sided accessory pathway
- (NB LV hypertrophy is not a cause)
When do you get right axis deviation?
- Normal finding in children and tall thin adults
- RV volume/pressure overload: RV hypertrophy, ASD, VSD, pulmonary embolus
- Lung pathology: COPD, PE
- Dextrocardia
- Wolff-Parkinson-White syndrome - left sided accessory pathway
When do you get extreme right axis deviation?
- Lead transposition
- Ventricular tachycardia
- Emphysema
- Hyperkalaemia
- Paced rhythm
What does atrioventricular dissociation indicate?
Complete heart block
(3) types of abnormalities of the QRS complex you can see on ECG
–Voltages eg. increased in LV hypertrophy, decreased in cardiac amyloidosis
–Q waves
–Conduction eg. left or right bundle branch blocks
How do you diagnose LVH on ECG “on voltage criteria”?
- Sum of S in V1/V2 & R in V5 or V6 (whichever is larger) ≥ 35 mm (7 large squares)
- or R in aVL ≥ 11 mm
NB: Echocardiography is a more accurate test for LV hypertrophy than ECG criteria alone
What are pathological Q waves?
–marker of electrical silence which implies established full thickness death of myocardium i.e scar
– > 25% height of the corresponding R wave
(and/or > 40 msec width and > 2mm in depth)
–Present in more than 1 contiguous (adjacent) lead
Classic morphology for LBBB on ECG
–“WilliaM” – W in V1(often not obvious) and M pattern in V6
–Inverted T waves lateral leads V5-V6, I, aVL
–No septal Q waves
Classic morphology for RBBB on ECG
–“MarroW” – M (rSR’) pattern in V1 and W in V6
–Inverted T waves V2-V3
–Slurred S wave in V6
(4) causes of ST segment changes
– Myocardial ischaemia/infarction
–Pericarditis (widespread ST segment elevation)
–LV hypertrophy with “strain” pattern (ST segment depression)
–Drugs eg. digoxin
Inferior leads of ECG
II, III, aVF
Lateral leads of ECG
High lateral: I, aVL
Lateral: V5-6
Anteroseptal leads of ECG
V1-4
Briefly discuss the progressino of acute ischaemic changes seen on ECG
- ST elevation (a key sign of acute myocardial infarction requiring urgent treatment)
+/- T wave inversion (often persists long term)
- Q waves: if full thickness infarction (previous infarction)
How does pericarditis present on ECG?
Widespread saddle shaped ST elevation
What does horizontal ST depression suggest?
significant myocardial ischaemia
What is a “strain” pattern on ECG?
ST depression with T wave inversion
(3) causes of T wave abnormalities
–Myocardial ischaemia
–LV hypertrophy/strain, digoxin effect
–Systemic issues eg. electrolyte imbalances (K+,Mg2+, Ca2+)
What (2) morphologies of T waves are most useful in diagnosing MI?
Biphasic or inverted T waves
Briefly describe Wolff-Parkinson White syndrome
- structural abnormality
- consequences
- (2) ECG changes
Accessory pathway bypasses atrioventricular node
- leads to earlier (pre)-excitation of the ventricle than would occur with conduction through normal pathway
- may lead to rapid regular tachycardias
ECG:
- Short PR interval
- Delta wave reflecting pre-excitation (early excitation) of the ventricle
