Basic 12 lead EKG Flashcards
How many leads are in a 12 Lead ECG?
12 Lead is actually 10 leads: 4 Limb and 6 Chest.
What areas do V1 and V2 represent on the ECG?
V1, V2 = RV
What areas do V3 and V4 represent on the ECG?
V3, V4 = septum
What areas do V5 and V6 represent on the ECG?
V5, V6 = L side of the heart
What does Lead I represent on the ECG?
Lead I = L side of the heart
What does Lead II represent on the ECG?
Lead II = inferior territory
What does Lead III represent on the ECG?
Lead III = inferior territory
What does aVF represent on the ECG?
aVF = inferior territory (remember ‘F’ for ‘feet’)
What does aVL represent on the ECG?
aVL = L side of the heart
What does aVR represent on the ECG?
aVR = R side of the heart
What does the P-wave represent in an ECG?
Atrial contraction
What does the PR interval represent in an ECG?
The time taken for excitation to spread from the Sino-atrial (SA) node across the atrium and down to the ventricular muscle via the bundle of His.
What does the QRS complex represent in an ECG?
Ventricular contraction
What does the ST segment represent in an ECG?
Ventricular relaxation
What does the T-wave represent in an ECG?
Ventricular repolarization
What are the first three steps in reading an ECG?
- Patient details
- Situation details
- Rate
- Rhythm
- Axis
- P-wave and P-R interval
- Q-wave and QRS complex
- ST segment
- QT interval
- T-wave
What information is included in patient details for an ECG?
- Patient’s name
- date of birth
- hospital number
- location
Why is the location of the patient important when reviewing ECGs?
It ensures that they can be moved to a higher dependency area if appropriate.
What details should be included in situation details for an ECG?
When the ECG was done, the time, ECG number if part of a series, and relevant clinical details such as:
If you are concerned that there are dynamic changes in an ECG it is helpful to ask for serial ECGs (usually three ECGs recorded 10 minutes apart) so they can be compared. These should always be labelled 1, 2 and 3.
* Did the patient have chest pain at the time?
* Or other relevant clinical details. For example, if you are wanted an ECG tolook for changes of hyperkaliemia, note the patient’s potassium level on
the ECG.
How can the rate be calculated on an ECG?
Count the number of QRSs on one line and multiply by six, or count the number of large squares between R waves and divide 300 by this number.
What is a more accurate way to report the rate in atrial fibrillation?
Report a rate range rather than a single value.
How can you assess rhythm on an ECG is ?
Determine if the rhythm is regular or irregular. If irregular, identify if it is regularly or irregularly irregular.
What is the ‘paper test’ for assessing rhythm on an ECG?
Place a piece of scrap paper over the ECG, mark a dot next to the top of a QRS complex, and slide the paper along the ECG. If the rhythm is regular, the dots will align with the tops of the QRS complexes.
What does the axis on an ECG represent?
The axis is the sum of all the electrical activity in the heart, with contraction traveling from the atria to the right and left ventricles.
Where does the normal axis lie and why?
The normal axis lies to the left because the left ventricle is larger and more muscular.
What indicates a normal axis on an ECG?
If the net deflections in leads I and aVF are positive, then the axis is normal.
What indicates right axis deviation on an ECG?
If lead I has a net negative deflection while aVF is positive, then there is right axis deviation.
What indicates left axis deviation on an ECG?
If lead I has a positive deflection and aVF has a negative deflection, then there is left axis deviation.
What are some causes of left axis deviation?
- Can be normal if diaphragms are raised in ascites, pregnancy.
- left ventricular hypertrophy (LVH),
- left anterior hemiblock,
- inferior myocardial infarction,
- hyperkalaemia
- ventricular tachycardia (VT).
- paced rhythm
What are some causes of right axis deviation?
- normal in children or young thin adults
- right ventricular hypertrophy (RVH) due to respiratory disease
- pulmonary embolism (PE)
- anterolateral myocardial infarction
- left posterior hemiblock (rare)
- septal defect.
How can you assess the P-wave on an ECG?
Check if a P-wave is visible. In atrial fibrillation, atrial flutter, or junctional tachycardia, it may not be visible.
What does it indicate if P-waves are not associated with QRS complexes?
- P-waves not associated with QRS complexes indicate complete heart block.
- then assess P wave morphology
What is ‘p mitral’ and what does it indicate?
A notched (or bifid) P-wave known as ‘p mitral’ indicates left atrial hypertrophy, often caused by mitral stenosis.
What is ‘p pulmonale’ and what does it indicate?
Tall peaked P-waves called ‘p pulmonale’ indicate right atrial hypertrophy, often secondary to tricuspid stenosis or pulmonary hypertension.
What is ‘pseudo p-pulmonale’?
‘p pulmonale’ seen in hypokalemia.
What can a prolonged PR interval indicate?
A prolonged PR interval may indicate first degree heart block.
What can a shortened PR interval indicate?
A shortened PR interval may occur with rapid conduction via an accessory pathwa, eg. Wolff Parkinson White syndrome.
What is a q-wave?
A q-wave is an initial downward deflection in the QRS complex. They are normal in left-sided chest leads (V5, 6, lead I, aVL) as they represent septal depolarization from left to right, as long as they are <0.04secs long (1 small square) and <2mm deep.
When are q-waves considered pathological?
If q-waves are larger than 0.04 seconds or present in other leads, they are pathological.
What is the normal duration of a QRS complex?
The QRS complex normally lasts for < 0.12 secs (3 small squares).
What are some causes of a wide QRS complex?
- bundle branch blocks (LBBB or RBBB),
- hyperkalemia
- paced rhythm
- ventricular pre-excitation (e.g. Wolf Parkinson White)
- ventricular rhythm
- tricyclic antidepressant (TCA) poisoning.
What conditions can cause a small QRS complex?
The QRS may be small in pericardial effusion, high BMI, emphysema, cardiomyopathy, and cardiac amyloid.
How about when QRS is tall, what can happen?
- LVH left venricular hypertrophy
- The height of the R wave in V6 + the depth of the S wave in V1 >35mm is suggestive of LVH.
Beside LVH, what else tall QRS indicates?
young, fit, thin people
What does ST segment elevation indicate?
- ST elevation indicates infarction
- To be significant the S-T segment must be depressed or elevated by 1 or more millimeters in 2 consecutive limb leads or 2 or more millimeters in 2 consecutive chest leads. Look out for reciprocal changes.
What does ST segment depression usually indicate?
- ST depression is normally due to ischemia.
- may also be seen in dig toxicity. the ST depression wil be down sloping
What is high-takeoff ?
- High-takeoff, also known as benign early repolarization, is widespread concave ST elevation, often with a slurring of the j-point, most prominent in leads V2-5, and is benign
- usually in young healthy people
How can high-takeoff be differentiated from myocardial infarction?
High-takeoff ST segments are:
* concave,
* most prominent in V2-5,
* have a slurred start (j-point),
* are usually minimal compared to the amplitude of the t-wave,
* have no reciprocal changes,
* and do not change over time.
What is the QT interval?
The QT interval is the time between the start of the q-wave and the end of the t-wave.
What is the corrected QT interval (QTc)?
QTc is the QT interval that is corrected for heart rate
How can you quickly check if the QTc may be lengthened?
If the t-waves occur over halfway between the QRS complexes, the QTc may be lengthened.
Why is identifying a long QTc interval important?
A long QTc interval is especially important to identify in patients with a history of collapse or transient loss of consciousness.
What are some drug-related causes of long QT?
- Tricyclic antidepressants TCAs,
- Terfenadine,
- Erythromycin,
- Amiodarone,
- Phenothiazines,
- Quinidine
What metabolic conditions can cause long QT?
- Hypothermia,
- Hypokalaemia,
- Hypocalcaemia,
- Hypothyroidism
What familial syndromes are associated with long QT?
- Long QT syndrome,
- Brugada syndrome,
- Arrhythmogenic right ventricular dysplasia
What are some other non-familial causes of long QT?
Ischemic heart disease (IHD), Myocarditis
What are normal variants of T-wave inversions?
- Normal variant
- commonly Inverted in aVR and V1, often in V2 and V3 in Afro-Caribbean descent
What conditions can cause T-wave flattening or inversion?
- Ischemia,
- Ventricular hypertrophy (strain),
- LBBB,
- Digoxin,
- Hypokalemia
Which electrolyte imbalance causes flattened T-waves?
Hypokalemia
What are classic ECG changes seen in hyperkalemia?
Small P-wave, peaked T-wave, wide QRS
What ECG change in hyperkalemia suggests severe cardiac toxicity?
Widening of the QRS complex
Normal
Normal
STE in leads II, III, aVF
ST
SB
V-paced
complete heart block
hyperkalemia
STE V3, V4 - anterior MI
ST depression in V1-V4 —> posterior MI