Lecture 1: Dysrhythmias Flashcards
define depolarization
process where resting membrane potential of heart becomes more positive. occurs when Na and Ca2+ ions flow into cells leading to rapid change in cell’s electrical charge.
heart sends signal, causing cells in atria and ventricles to depolarize. causes the muscle fiber to contract.
this initiates the contraction of heart muscle, which pumps blood through the chambers.
inside of cell becomes more positive (sodium, potassium and chloride needs to move for contraction for heart to beat)
Ectopic
(SA node is the beginning point of domino effect) we have a coordinated contraction and if the impulse starts in a different locations then it is ectopic (still falls but not right sequence and not as effective)
when heart beats out of its usual rhythm or place.
repolarization
is the process where cell’s membrane potential returns to its resting, negative state after depolarization. during repolarization, K ions move out of cell restoring internal -‘ve charge.
after heart muscle contracts, electrical charge within cells begins to return to baseline. Preparing cells for next depolarization.
allows heart muscle to relax after contraction, so it is ready to contract again.
(all electrolytes move back to where they need to be so it can happen again) happens very quickly
permeability
(sodium, potassium, and chloride needs to pass) changing permeability affects this cycle (meds can alter this cycle)
absolute refractory period
(when sodium and potassium move back to where they need to be (there has not been enough electrolyte movement of electrolytes for depolarization to happen again)
“no entry zone”. time after heart muscle cell has depolarized when it cant fire again no matter what. gives heart time to rest and recover.
relative refractory period
(it could be set off, but not the same magnitude of depolarization if we are only part way through repolarization)
like a “half open door” for heart cells. heart cells can fire again, but only if signal is strong enough. time when heart is still recovering but if the heart gets a big enough push it could beat again.
describe to me how blood moves thru the heart (this is a horrible cue card going to have to whiteboard + look at notes)
- R atrium: blood comes from body, low in o2 into R atrium
- R ventricle: blood moves to the right ventricle
- lungs: r ventricle pumps blood into lungs to get oxygen
- L atrium: oxygen-rich blood returns to heart, entering the L atrium
- L ventricle: blood moves to the L ventricle
- Body: L ventricle pumps oxygen - rich blood out to the body
R atrium -> R ventricle -> lungs -> L atrium -> L ventricle -> body
describe the hearts automaticity
heart can contract by itself, independently of any signals or stim from body. heart contracts in response to electrical current conveyed by conduction sys.
heart attacks SA node
every cell in the heart can start the domino effect
3 main parts of the conduction system for the heart
- (sinoatrial) SA node
- AV node
- conduction fibers within the ventricle, specifically the bundle of His, bundle brances, and Purkinje fibres
describe to me the intrinsic pacemaker rates of cardiac conduction tissue
- If everything is good, SA node is the pacemaker (60-100 beats per minute)
- SA node sends signals to depolarize, the other parts won’t have a chance to take over because everything is synchronized and beautiful
- No SA node, then AV node will say (hey this is not good (less than 60 beats a min), it will start depolarizing at a rate of 40-60
- Less than 40 per minute, then the Purkinje fibers will start (40-15)
- It is a failsafe method
This is dysrhythmia
describe cardiac monitoring and telemetry (6 lead)
- Top is cardiac monitoring strip (usually they have 2)
- Connected straight to wall and monitored at bedside
Portable units around their neck (wires connect to stickers on chest)
describe an ECG
- Heart from different views
- Tracings of electrical energy as it moves towards a lead
- Looking from a different view of the heart
- Energy moves as it depolarizes (energy coming towards me is more positive)
- Going up means net energy is moving towards it
- Positive when coming towards the lead (positive deflection), then drops when it goes away (negative deflection)
- Ventricles (bigger QRS) is representative of the current as it goes through (bigger whether positive or negative)
- Think of the lead as an eye
Lead 2 is most easy to read
describe cardiac monitoring
- Emergency (chest pain, SOB) to see changed (shows PQRST)
- Quick view to show us anything obvious with the heart
- Lets us know HR, disease or injury, pacemaker function, evaluates if a med is working
Evaluate if a patient is having an MI
3 lead or 5 lead
describe a 12 lead ECG
One is bisecting and the other looks at planes (look at the diagrams)
describe 5 lead cardiac monitoring (pic on the slides insert later)
- LL left leg
- RA right arm, etc
- Colour coordinated
White to the right, smoke (black) above fire (red), brown at the chest, white clouds over green grass
define afterload
what are we pumping against
(pressure or resistance against which ventricles pump to eject blood)
Preload
force exerted at the end of diastole (filling), and we are now going to contract, once they are filled that is preload. Preload determines how effective our contraction is going to be
describe contraction
mechanical event
ability of cardiac cells to shorten, causing cardiac muscle contraction in response to electrical stim
venous return
blood amount going into right atrium
stroke volume
amount of volume moved out of ventricles
ejection fraction
% of blood pumped out of ventricle with each contraction (each ventricle ejects a % (50-80%) (more volume in ventricle the more volume)
cardiac output
stroke volume (that goes out with each contraction) then multiple by contraction (HR per minute)
diastole
rest period with filling
term implies ventricular diastole
bp
force exerted by circulating blood volume