Cardiac Pacemakers
new 10 Oct 12
D McMahon
History –
1952 - Zoll: stimulation of heart thru chest wall
1957 - Lillehei: direct stimulation by leads on the
heart from an external pacemaker
1958 - Greatbatch: made first fully implantable pacemaker
1986 - Medtronic Corp: first rate-responsive pacemaker
The problem: Arrhythmias
Types of arrhythmia:
> Conduction Problem
- delay at the SA node pacemaker
- deflected path of the signal
- block of the path
1° Block: long delay
2° Block: intermittent block of the signal
3° Block: complete blockage of the signal
> Problem at the Origin of the Signal
- erratic rate at the SA node
- multiple pacemaker sites
- high rate (“sinus tachycardia”)
- low rate (“sinus bradycardia”)
Examples :
Pacemaker Types:
Entire unit surgically installed within the chest
External Invasive:
Leads in the heart, pacemaker assembly external
Entire pacemaker external; signal thru the chest wall
Automatic Implantable Cardiac Defibrillator (AICD):
Not a true pacemaker, but monitors the heart rate and sends a
defibrillation signal if and when the heat goes into fibrillation
Pacemaker Modes:
Asynchronous: provides pulses at a fixed rate
Demand: provides pulses when the heart fails to beat
Rate-Modulated: provides pulses based on the
heart’s current activity
Pacing markers
Modern implantable pacemakers are
programmable through telemetry or
magnetic signaling, and most store months
worth of history of heart activity which can
be retrieved noninvasively.