WK7 - ECG Flashcards
Which side of heart receives what blood?
R side receives de-oxygenated blood
L side received oxygenated blood
What are the layers of the heart? Start from the heart chamber
- Heart chamber
Heart wall: - endocardium
- myocardium
- visceral layer of serous pericardium (epicardium)
- pericardial cavity
- parietal layer of serous pericardium
- fibrous pericardium
2 main layers:
Inside = myocardium
Outside = pericardium
What are the coronary arteries?
- R & L coronary arteries emerge from aortic root sinus to supply blood to heart muscle
- L main coronary artery divides…
- L ANT descending (LAD)
- circumflex (LCx)
What is the coronary blood flow of LCA?
- main LCA
- cirucmflex branch
- ANT interventricular (descending) branch
- atrioventricular branch of circumflex
- lateral branch
- posterolat branches
- perforating branches to interventricular septum
What is the coronary blood flow of RCA?
- RCA - R ANT oblique position
- SA Node
- R main CA
- marginal branches
- AV node
- LV
- POS interventricular (descending) branch
What are the 4 primary characteristics of cardiac cells?
- excitability - EXT stimulus response (chemical, mechanical, electrical etc)
- contractility -shorten/return to original length
- automaticity - spontaneously initiate electrical impulse w/o being stimulated for another source (e.g. nerve)
- conductivity - receive electrical impulse/conduct to adjacent cardiac cell
Explain the conduction of cardiac impulses through the heart.
- electrical events preceed mechanical events
- SA node depolarisation
- RA (1st) and LA (2nd)
- atrial contraction
- AV node (delays conduction for ventricular filling from atrial contraction)
- Bundle of HIS –> R & L bundle branches –> purkinje ribres
- ventricular contraction
What are cardiac cells?
- form/conduct electrical impulses = depolarisation/contraction of heart
- contract in all-or-none manner
- possess short absolute/relative refractory periods to aid in hearts pumping action
What is on the axis of an ECG graph? Explain reference pause and how to read the boxes.
x = time
y = amplitude
1mV (10mm high) = reference pulse
One large 5mm*5mm box = 0.2s (200ms) time and 0.5mV amplitude
One small 1mm*1mm block = 40ms time and 0.1mV amplitude
Why is it important to obtain a 12 lead ECG?
To gain electrical activitiy of the heart muslce via..
1. 2 electrodes (+ve and -ve) - bipolar
2. 1 +ve electrode and 1 zero reference point - unipolar
What is Einthoven’s triangle?
It is made up of the limb leads I, II and III to make up the bipolar leads.
Einthoven’s Law states: Lead I + Lead II = Lead III
Einthoven reversed polarity of Lead II to view complexes upright
What are the different leads in an ECG?
- 3 standard limb leads = bipolar (I, II, III)
- 3 augmented leads = unipolar (aVR, VL, aVF)
- 6 precordial leads = unipolar (V1, 2, 3, 4, 5, 6)
Ground provides path least resistance for interference.
What is artefact (noise/intereference)?
Caused from suboptimal acquisition of data
- Patient movement - gross movements as well as tremor/shivering
- AC interference (alternating current)
- loose electrodes
- biotelemetry
- cardiac compressions
What is the P Wave?
atrial depolarisation = atria contracts
* sinus node depolarised
LOCATION: precedes QRS complex
CONFIGURATION: upright, rounded and smooth
BE AWARE: absent or inverted P waves = electrical current generated elsewhere than SA node
What is the PR interval?
Represents atrio-ventricular conduction time
LOCATION: beginning of P wave to beginning of Q wave (if no Q wave then to R wave)
CONFIGURATION: usally isoelectric
DURATION: 0.12-0.2s
Look at leads with clear P wave
