Pacing terms and definitions

ECG/EKG

surface electrogram

IEGM

intracardiac electrogram: internal view

intrinsic

inherent or belonging to the heart itself; sometimes called native

intrinsic beat

naturally occurring heart beat

intrinsic rate

naturally occurring heart rate

isoelectric line

flat line on ECG indicating period of time when there is no electrical activity

depolarization

sudden change in electrical potential from negative to positive

action potential depolarization phase

phase zero

repolarization

recovery process of excitable tissue following depolarization; getting ready to stimulate again

action potential repolarization phase

phase 1-3

T-wave

ventricular repolarization

morphology

shape of a waveform

biphasic

wave form morphology from positive and negative deflection

normal ICD shock

biphasic

ectopic focus

source of a stimulating impulse for the heart other than SA node

typical ectopic foci

atria, av junction, ventricles

arrhythmia or dysrhythmia

any disturbance in the normal cardiac rhythm; abnormal origination/discharge or abnormal conduction of electrical impulse

“most” correct term since ancient times

arrhythmia

asystole

complete absence of ventricular contractions in the heart (cardiac standstill)

syncope

fainting or a black out spell caused by insufficient blood supply to the brain

artifact

signal produced by paced output or external signal not from the heart

automaticity

ability of tissue to spontaneously generate an electrical impulse and propagate an action potential; inherent property of SA node

chronotropic incompetence

inability of the heart to regulate its rate appropriately in response to physiological stress (exercise)

AV dissociation

condition in which atria and ventricles beat independently of each other without synchronization; problem

AV synchrony

1:1 ratio of atrial contractions to ventricular ; coordination allows atrial contraction to augment the filling of the ventricles (goal)

pacemaker syndrome

adverse hemodynamic or electrophysiological consequences associated with an electrically normal pacing system; symptomatic only mild to severe

ex: blood pushed in weird directions or single chamber ppm

acute

first 6 weeks after implant when leads are at risk of dislodgment; thresholds measured during first weeks after implant of new lead

chronic

after device and components have healed; majority of devices lifecycle

programmer

equipment used to interface with an implanted device

Pacing System Analyzer

added to programmers as accessory to run tests

active fixation leads

screw-in or suture-on (screw)

passive fixation leads

tined or finned; lead anchoring into muscle of heart (hook)

endocardial leads

most common

epicardial or myocardial leads

used in pediatrics

bipolar

see/effect not enough; cathode and anode in lead

unipolar

see/effect too much; cathode in lead and anode in can

bipolar lead types

co-axial or co-radial and bifrucated or inline

stylet

insertable wire to steer leads; skeleton because rigid and steerable

guidewire

wire inserted before lead like train tracks; put in place in patient and lead goes over

distal

farthest point from reference

distal electrode on pacing lead connectors

tip electrode

proximal

closest point from reference

proximal electrode on pacing lead

ring electrode

cathode

negative pole/electrode

pacing lead cathode electrode

distal end

negative terminal on a pulse generator connector block or negative terminal of battery

cathode

anode

positive pole/electrode

where is unipolar pacing system anode

pulse generator

where is bipolar pacing system anode

proximal ring electrode on pacing system

positive terminal on pulse generator connector block or positive terminal of battery

anode

primary components of leads

insulation, electrode, conductor, connector

percutaneous introducer

thin, hollow tube used for easy passage of the endocardial lead through the skin, into a blood vessel, then advancing the lead into the heart

fluoroscope

device used routiely during lead placement which provides real time x-ray images on a monitor

what does fluoro allow physician to see

transvenous passage and placement of lead into heart

afterpotential/polarization

residual charge present at the electrode/myocardial interface immediately upon completion of a pacing stimulus

cardiac implantable electronic devices

pacemaker (insertable pulse generator), ICD, CRT, implantable loop recorder, implantable cardiac monitor

AKA: the can, the battery, the shock box

shock box

at risk for sudden cardiac death (PPM all the way down and shock all the way up)

leadless pacemaker

active fixation

implantable loop recorder or cardiac monitor

used to monitor for longer periods of time

reed switch

solid state magnet detector; initiates pacing in a non-tracking mode and starts a battery test in PPM

what is used to detect magnetic fields in IPG or ICD

reed switch

zener diode

protect circuit by shunting power away so PPM does not explode when you get shocked

CMOS

complementary metal oxide-semiconductor; brain of CIED

capacitor

device that can store an electrical charge, made of two conductors separated by an insulator; in pulse generator circuitry used to store energy until it is needed for a pacing stimulus when it releases the energy to the output circuit

capacitor in pacing

used in both battery and pulse generator circuitry; how ppm does more than battery says it can (quick charge, quick dump)

feedthrough

insulated electrical pole in the pulse generator connector that serves to connect the pulse generator’s internal circuitry to pacing lead

what is hermetically sealed

feedthroughs to prevent leakage of fluids into pulse generator and are typically made of glass or ceramic

hermetic seal

seal that prevents penetration of fluid or vapor

theoretical longevity

calculated, projected total service life of the pulse generator from beginning of life to recommended replacement time; projected battery life

housekeeping or quinescent current

current utilized when not pacing; used for ongoing tasks like monitoring intrinsic rhythm and logging date

“background functions” and reason why ppm will die on the shelf

reducing output from 4V to 2V

may increase battery longevity 4-6 years still with housekeeping needs

BOL

beginning of life; deliverable portion of battery capacity; entire functional life

ERI

elective replacement indicator; set by manufacturer as point in PPM service life when replacement is recommended

how long after ERI will device function

3-6 months

can device go from ERI to BOL

no, ERI is latched

indications of ERI or RRT

change in rate, mode, pacing function, or by indicator via programmer and/or device itself

EOL

end of life; when battery or ppm or icd reaches predetermined level; device can no longer be relied upon for safe and effective pacing

indications of EOL

change in demand and magnetic rates

base rate

rate at which the pulse generator paces in absence of intrinsic activity

base rate units

pulse per minute

low rate

base rate; programmable

MSR

max sensor rate; fastest rate a device will generate pacing impulses based on detected patient activity

MTR

max tracking rate; fastest rate a device will pace the ventricles while maintaining AV synchrony

upper rate

max sensor rate or max tracking rate

output

electrical stimulus delivered by the pulse generator and usually defined in terms of pulse amplitude (V) and pulse width (ms)

output in pacing

refers to electrical output of device

cardiac output

amount of blood pushed through heart

volt

force with which electrical current is driven; pulse amplitude

millivolt

basic unit of pulse generator sensitivity (1/1000 of volt)

millisecond

basic unit of measurement of time in pacing (1/1000 of a second)

capture

successful depolarization and contraction of a cardiac chamber caused by pacemakers output pulse

one to one capture

each pacemaker output pulse results in a contraction of appropriate chamber

asynchronous

type of pacing in which output pulses are delivered at a fixed rate with no modifications due to sensing

asynchronous modes

AOO, AOOR, VOO, VOOR, DOO, DOOR

synchronous

type of pacing in which output pulses are delivered in response to a sensed event, usually after an appropriate timing delay

ex: atrial synchronous pacing provides ventricular pacing in response to sensed atrial activity

timing cycle

one of the specific and predefined timing periods of various aspects of the pacing mode like atrial escape interval

timing cycle unit

millisecond

alert period

portion of the pulse generator’s timing cycle during which the pulse generator can sense and respond to intrinsic cardiac activity

rate modulation/response

ability of pacemakers to increase pacing rate in response to physical activity or metabolic demand

how do rate modulated pacemakers work

utilize some type of sensor other than sensing intrinsic atrial depolarization