Pacemakers Flashcards
Indications for pacemakers
- Symptomatic bradycardias
- Sinus node dysfunction, sick sinus, tachy-brady, sinus arrest
- AV blocks
- Post cardiac transplantation
- Hypersensitive carotid syndrome
- Vasovagal syndrome
- Long QT
- LV dysfunction, dilated cardiomyopathy
- Overdrive pacing to suppress fast rhythms
What do pacing circuits consist of?
1) Pulse generator
2) Leads
3) Electrodes
1) Unipolar circuit
2) Bipolar circuit
What is a pulse generator?
Electrical source which initiates the impulse causing depolarization. Contains controls and settings and a sensing mechanism detecting and interpreting info about pt’s intrinsic activity
What are leads (wires)?
Conduct electrical stimuli from the pulse generator to the myocardium. Also transmit sensing info from heart to the pulse generator
What are electrodes?
Exposed metal ends of the lead wires that conduct the impulse to the heart.
1) Negative = Cathode
2) Positive = Anode
What are the two types of pacing circuits?
1) Unipolar
- –> Only one electrode in direct contact with the heart (cathode). The other electrode (anode) is located outside of heart. Impulse travels from pulse generator to the myocardium then through body tissue to the positive electrode.
2) Bipolar
- –> Both positive and negative electrodes in contact with heart
What are the modes of pacing?
1) Transvenous pacing
- –> Pacing electrode advanced via catheter or wire through a vein and into the endocardium of right atrium or ventricle
2) Epicardial
- –> Thin stainless steel wires coated in insulation that are attached through surgery to epicardial surface
3) Transcutaneous
- –> Large pads placed on pt chest wall, temporary pacing used in emergency situations. Much higher output necessary, pt may require analgesia
What are the three pacemaker functions?
1) Firing (pacing)
2) Capturing
3) Sensing
What is pacemaker firing?
Pulse generator fires an impulse which produces pacer spike on ECG.
Nursing responsibility to ensure:
- Firing occurred when it should
- Pacemaker is not firing when the heart is working properly
What is pacemaker capture?
Depolarization occurs when myocardium responds appropriately to a pacing stimulus. Atrium, ventricle, or both can be paced. Capturing occurs every time a pacer spike is followed immediately by electrical activity.
If the ventricle is paced, what will the QRS look like?
Will look wide and bizarre because conduction occurs through an abnormal ventricular route
What is pacemaker sensing?
Ability to “see” when intrinsic depolarization occurs. We then do not want the pacemaker to fire and capture the heart. Once pulse generator senses intrinsic activity, it will either:
1) Inhibition –> Prevent firing
2) Triggering –> If an intrinsic beat is NOT sensed, pulse generator will fire
What is demand pacing?
Most common mode, pulse generator sees all intrinsic activity and fires IF THERE IS NO INTRINSIC BEAT.
What is asynchronous pacing?
Pulse generator fires regardless of pt’s own intrinsic beats. Sensitivity is either turned off or set to highest level so pacemaker does not see anything.
**If pacemaker fires on a T wave the pt may go into fatal arrythmia
How does magnetic activation work with permanent pacemakers?
MD may deactivate permanent pacemaker by placing a magnet over the pacemaker, changing the pacemaker to ASYNCHRONOUS MODE. Pre-set values are restored upon removal of magnet