Pacemaker terminology and definitions

A more detailed discussion of pacemaker technology is conducted elsewhere. This is a brief point-form summary. Some of these definitions have been asked about in the SAQs before, eg. in Question 29 from the second paper of 2013 and Question 2 from the first paper of 2016. 

Definitions

Rate

• The pacing rate, in beats per minute.
• Usually set as a "backup rate"

Sensitivity

• Sensitivity of a pacemaker electrode is the minimum myocardial voltage required to be detected as a P wave or R wave, measured in mV.
• The lower the number, the more sensitive the pacemaker.
• The normal settings are 0.4-10mV for the atria, and 0.8-20mV for the ventricles

Output

• The output of a pacemaker is the current (in mA) which it produces as a brief pulse.

Capture

• Capture is the effective stimulation of cardiac depolarisation by the pacemaker

Pacing threshold or "Capture threshold"

• This is the minimum amount of current (in mA) required to initiate depolarization of the paced chamber.