Pacemakers Flashcards
What is a pacemaker?
Device to stimulate cardiac activity.
Don’t we already have pacemakers?
Yes, but sometimes the don’t work so well.
What two basic functions do pacemakers perform?
Sense cardiac activity
Pace
What are the basic components of pacemakers?
Generator and lead wires; those can be epicardial or endocardial.
What are the two basic categories of generators?
External and implantable
What other function might the generator provide besides routine pacing?
De-fibrillate
What is a Reed switch?
Switch in pacer controlled by magnetic field through skin.
What are the two fixation devices on pacer leads?
Tines and screws
Where is a pacemaker generator usually installed?
Under skin below left clavicle.
Name some indications for pacing:
Brady or tachy arrhythmias; 3rd degree heart block; cardiac surgery; asystole: heart dependent on pacer for any activity at all.
What is capture?
The pacer is able to bring about cardiac activity. (depolarization)
ECG will show if capture is effective.
What is capture dependent on?
Voltage; Condition of myocardium; Lead resistance
How do we know when we have capture?
Pacing spike is followed by a depolarization: QRS or P, depending
Define under-sensing:
Pacer doesn’t recognize intrinsic cardiac activity
Threshold too high
Define over-sensing:
Pacer responds to non-cardiac signals (hair-trigger)
Threshold too low
How do we recognize when proper capture isn’t happening?
Spike NOT followed by appropriate ECG activity.
What do the letters of the first, second, and third letters in the function code mean?
PSR: chamber paced (A or V or Dual); chamber sensed ( A or V or Dual); and response (Inhibit or Trigger)
How would a VVI pacemaker work?
Paces the ventricles, senses the ventricles, doesn’t pace if ventricles depolarize on their own.
How would a VAT work?
Paces ventricles; senses atria; paces when atrial depolarization is sensed.
How would DDD work?
Paces both, senses both.
Both responses are possible.
How would AAI work?
Paces atria; senses atria; doesn’t pace if atrial activity is sensed.
How are pacemakers programmed once implanted under the skin?
Magnetic pulses
What is a fusion beat?
Paced beat created along with intrinsic
What does a fusion beat look like on ECG?
Paced and intrinsic beats squashed together. Merged.
What goes wrong with pacers most often?
Lead wire damage
What is “twiddlers syndrome”?
Patient absent mindedly twiddles wires under skin, possibly damaging the wires.
