Cardiac Pacemakers

© D. J. McMahon 2012 rev 121010

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:

Implanted:Entire unit surgically installed within the chest

External Invasive:Leads in the heart, pacemaker assembly external

Transcutaneous:Entire pacemaker external; signal thru the chest wall

Automatic Implantable Cardiac Defibrillator (AICD):Not a true pacemaker, but monitors the heart rate and sends adefibrillation 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

AICD

pacemakers

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.