ECG Flashcards
Which direction does repolarisation spread in relation to depolarisation?
Opposite: outside-inside (epicardial – endocardial)
Where is lead 1,2,3
s the electrode in the following leads? (not augmented)
1. Lead 12. Lead 2 3. Lead 3
- Views heart from L side 2. Apex of heart 3. Views heart from the right bottom
What 2 factors determine the amplitude of the signal?
- Muscle mass is proportional to the amplitude 2. Position of electrode in relation to the ‘moving excitation’
What do the following waves represent? P wave:Q wave:R wave:S wave:T wave:
P wave: atrial depolarisationQ wave: septal depolarisationR: main ventricular depolarisation S wave: end of ventricular depolarisationT wave: ventricular repolarisation
What does it mean when the line is on the isometric baseline?
No signal
How does a signal become amplified? How many leads are amplified?
Amplifiers have one positive and one negative view:They take in the negative signal, invert it to make it positive and add it to the actual positive input.Sum up the ‘2 positives’ to create one amplified view 3 leads are amplified
Define a heart lead:How many cables are there and how many leads in an ECG?
Lead: electrical view of the heart10 cables, 12 views/leads
How many leads are there in the chest and limbs?How many limb and chest cables are there?
6 limb leads, 6 chest leads (V1-V6)6 chest cables4 limb cables, (black one generates no signal it is the ‘earth electrode’)
How could you calculate an irregular heart rate using an ECG?
- Count the number of peaks in 30 squares (equal to 6 seconds) and multiply that number by 10 to give you bpm2. Count the number of peaks in the bottom segment representing 10 seconds and X by 6
How many seconds is represented in each square on an ECG usually? What is the normal bpm?
0.2 seconds in each larger square, 0.04 seconds in each little squareNormal bpm is 60-100 bpm
Which wave is absent in atrial fibrillation?
P wave: representing atrial depolarisation
What can be indicated by a broad QRS complex?
It’s taking more time for excitation to pass through the ventricles. Indicates that the AP is being generated from somewhere elsewhere than the SA node (which generates APs quicker), and may be coming from the AV node or bundle of HIS
What does the segment between P-R represent? How many seconds and squares long is it usually and what does it mean if its longer?
It’s the time it takes for an AP to cause ventricular systole, typically 280 ms and the space between P-R should be 3-5 squares. >280 ms indicates a block
Explain the sinus arrhythmia phenomenon
It’s a normal phenomenon that means the breathing cycle changes your HR, this makes your HR appear ‘regularly irregular’ on an ECG. On inspiration: HR increases (diaphragm contracts and moves downwards, creating -ve pressure in the thoracic cavity and allowing more blood to enter the heart, so HR increases)On expiration: HR decreases
If part of the myocardium is temporarily short on oxygen, what can be seen on an ECG?
an ST-depression (reduced blood flow)
