Module 10 - Cardiac Therapy Flashcards
Indicate arrythmias that can be treated by defibrillator or PM
Ventricular tachycardia
- – Wide and distorted QRS.
- – If it is small deviations that continuously occur then use Pacemaker
Ventricular fibrillations
- Irregular fluctuations without QRS. No pump function
- need defibrillator
Explain the working mechanism of defibrilator
Restores the heart rhythm if you have fibrillations by an electrical shock through the heart muscle. This then causes a simultaneous depolarization of the ventricular heart muscle.
Explain the workings of a pacemaker
Set the pace to inadequate heart contractions due to electrical condution probelms. Do this with small deviations. It then ensures that the cardiac output increases again.
Main electrical components of defibrillator and pacemaker
Defib: RC circuit transformer resistor and capacitor And: --- discharge block, monitoring section, safety discharge, battery
Main components pacemaker
Switches, resistances, capacitors,
and
— battery, electronics, and universal connector system
Difference between monophasic and biphasic defibrillation
Current is deliverd in one direction for monophasic defib.
Current is delivered in two directions for biphasic defib. So stimulate both depolarization and repolarization of the ventricles
Difference between unipolar and bypolar pacemaker
Unipolar only has one lead, the way back is via the tissues, the heart or the thorax
Bipolar has two leads. Used more ofte. You can control the current better, and more locally
Explain the strength duration curve of a pacemaker and label rheobase and chronaxie
After a pacemaker is placed the settings need to be optimized. You always look at the strenght duration curve, voltage stimulation threshold over time.
Rheobase: the lowest voltage at infinite duration that just stimulates contraction
Chronaxie: 2 times rheobase. Optimal power setting
What is pacemaker code based on? Name the 4 codes, and the options
- Stimulation position: Atrium, ventricle, dual
- Sensing position: Atrium, ventricle, dual
- Post-sensing position: Inhibit, trigger, dual
- Complexity: Rate responsivity
What is VVI, what is AAI
VVI = stimulate in ventricles, sense is the ventricles, and inhibit, unless action is needed
AAI = stimulates in the atrium, senses in the atrium, and inhibits unless there is no p-wave
What is DDD
Stimulates in both the ventricles and the atria
Senses in both the atria and the ventricles
does it if there is no QRS complex
What is VVIR?
stimulates in the ventricles
senses in the ventricles
inhibits, unless there is no QRS
rate responsive, it responds/ is triggered by for example acceleration meter, so that the HR also increases since the pacemaker would not do that by itself
What is DDDR?
Stimulates in ventricles and atria
Senses in ventricles and atria
and can be inhibited and triggered in both areas by being rate responsive too. Such as is the case with VVIR, but then also for atria
What is the main risk of defibrillation?
- Having so many people in the loop that all have different kinds of roles.
- Also many things to take into consideration where things can go wrong. Hands-of during procedure, timing, rhythm, moist, correct positioning etc
- device itself: should be safely designed and checked.
What are the main risks of pacemakers?
- implementation related:
- —- risk of procedure, infection, allergic reaction - unipolar electrode
- —- can stimulate the muscle without wanting that to happen - timing problems
- —- desynchrony between atrium and ventricles disturbs pump function in the heart - incorrect settings
- —- failure to output: no spike
- —- failure to capture: does not sense correctly
- —- oversensing
- —- undersensing - it being implantable
- —- leads can break, pacemaker can just stop working. Need new operation then
