ECG interpretation Flashcards
What’s the normal adult heart rate?
60-100 bpm
How do you calculate the heart rhythm on an ECG if it is regular?
count the number of large squares present within one R-R interval, then divide 300 by this number
How do you calculate the heart rhythm on an ECG if it is irregular?
count the number of complexes on the rhythm strip, and then multiply this number by 6 to give you the average number of complexes in 1 minute
what are the 2 types of heart rhythm an individual can display?
regularly irregular or irregularly irregular
how can you see if the heart rhythm is regular or irregular?
mark out several consecutive R-R intervals on a piece of paper, then move them along the rhythm strip to check in the subsequent intervals are similar
what is a good tip to do if you are suspicious of an AV block?
map out the atrial rate and the ventricular rhythm separately, as you move along the rhythm strip you can see if the PR interval changes, if QRS complexes are missing or if there is complete dissociation between the two
what is the cardiac axis?
the overall direction of electrical spread within the heart
what is the cardiac axis in a healthy individual?
11 o’clock to 5 o’clock
what are the typical ECG findings for normal cardiac axis?
lead II has the most positive deflection compared to leads I and III
what are the typical ECG findings for right axis deviation?
lead III has the most positive deflection and lead I should be negative
what is right axis deviation associated with?
right ventricular hypertrophy
what are the typical ECG findings for left axis deviation?
lead I has the most positive deflection, leads II and III are negative
what has left axis deviation associated with?
heart conduction abnormalities
what are the 4 steps you should take when looking at the P waves?
- are the p waves present?
- is the p wave followed by a QRS complex?
- do the p waves look normal? - duration, direction and shape
- if the p waves are absent, is there any atrial activity
what would absent p waves and an irregular rhythm indicate a diagnosis of?
atrial fibrillation
How long should the PR interval be?
between 120-200ms (3-5 small squares)
how many milliseconds is a small square?
40ms, 0.4 s
what does a prolonged PR interval suggest?
A PR interval >0.2s suggests the presence of a atrioventricular delay (AV block)
What would be seen on an ECG with a first-degree heart block?
A fixed prolonged PR interval >200 ms
what would you see on an ECG with a second-degree heart block (type 1)?
Progressive prolongation of the PR interval until eventually the atrial impulse is not conducted and the QRS complex is dropped. This repeats
what would you see on an ECG with a second-degree heart block (type 2)?
a consistent PR interval duration with intermittently dropped QRS complexes due to the failure of conduction, typically repeating cycle of every 3rd (3:1) or 4th (4:1) P wave
what would you typically see on a third-degree AV block?
presence of P waves and QRS complexes that have no association with each other
where do narrow-complex escape rhythms originate?
above the bifurcation of the bundle of His
where do the broad-complex escape rhythms originate?
below the bifurcation of the bundle of His
where does the first-degree AV block occur?
between the SA node and the AV node
where does mobitz I Av block occur?
In the AV node
where does mobitz II AV block occur?
after the AV node in the bundle of His or purkinje fibres
where does third-degree AV block occur?
occurs at or after the AV node resulting in a complete blockade of distal conduction
what syndrome is a shortened PR interval associated with?
Wolff-Parkinson white syndrome, as an accessory pathway is associated with a delta wave
what 3 characteristics of a QRS wave do you need to consider?
width, height, morphology
what causes a narrow QRS complex?
when the impulse is conducted down the bundle of His and the Purkinje fibre to the ventricles
what causes a broad QRS complex?
an abnormal depolarisation sequence, for example a ventricular ectopic or a bundle branch block
what defines a small QRS complex?
<5mm in the limb leads or <10mm in the chest leads
what does a tall QRS complex imply?
ventricular hypertrophy
what syndrome does the delta wave indicate?
Wolff Parkinson white syndrome - indicates early ventricle stimulation
what is the slurred upstroke of the QRS complex?
delta wave
what does Q waves with T wave inversion suggest?
previous anterior myocardial infarction
what can poor progression of S > R through to leads V5 to V6 be a sign of?
previous MI but also v large people due to poor lead position
where is the J point segment?
where the S wave joins the ST segment?
what defines ST-elevation?
when the St segment is greater than 1mm in 2 or more contiguous limb leads or >2mm in 2 or more chest leads
what is ST elevation most commonly caused by?
acute full-thickness myocardial infarction
What defines ST depression in > 0.5mm in > 2 contiguous leads indicate
myocardial ischemia
what can a tall T wave be associated with?
hyperkalaemia and hyperacute STEMI
what lead are T waves normally inverted?
V1
what pathology can inverted T waves suggest?
Ischaemia,
Bundle branch block (V4-6 in LBBB and V1-v3 in RBBB)
PE
Left ventricular hypertrophy (in lateral leads)
hypertrophic cardiomyopathy
general illness
what can biphasic T waves be indicative of
ischaemia and hypokalaemia
what may flattened t waves represent?
ischaemia or electrolyte imbalance
what would you see on an ECG with a patient with unstable angina?
no ST elevation and no pathological changes
what would you see on an ECG with a patient with nSTEMI
ST depression in a region, T wave inversion, pathological q waves,
what would you see on an ECG with a patient with a STEMI?
ST elevation, LBBB,
what would you see on an ECG with a patient with a STEMI?
ST elevation, LBBB,
what would you see on an ECG with a patient with atrial fibrillation?
absent p waves, narrow QRS complexes, the irregularly irregular ventricular rhythm
what would you see on an ECG with a patient with supraventricular tachycardia?
narrow QRS complex, a QRS followed immediately by a T wave, QRS, T wave etc
what would you see on an ECG with a patient with ventricular tachycardia?
broad QRS complexes >0.12
