Pacemakers. Flashcards
almost always on the
right side of the heart.
indications for pacing:
symptomatic complete heart block, asymptomatic complete heart block, symptomatic sinus bradycardia (sick sinus syndrome), chronic incomplete heart block, persistent advanced heart block in acute MI, symptomatic congenital heart block, complete heart block.
benefits of pacing:
healthy heart rhythm = increased cardiac output = improves cerebral and total body perfusion = symptomatic relief = patient benefits.
pacemakers:
control discharge, time discharge, and recognize native activity of the heart.
tip electrode:
delivers a stimulus to the myocardium and detects native intra-cardiac signals.
unipolar leads
negative in heart
bipolar leads
positive and negative in heart
voltage:
potential (force) capable of doing work; battery voltage is a function of the mounts of charged material placed inside the battery cell by the manufacturer.
higher voltage =
stronger push on electrons.
resistance:
an opposition to current (tries to stop the flow).
low resistance =
high current.
high resistance =
low current. fibrosis, scarring.
resistance is:
primarily a function of cardiac tissue and electrode position.
current:
the flow of electrons leaving the battery (pacemaker); garden hose analogy; measured in milliamperes; program the voltage to get the current.
current vs voltage:
current is a result of voltage; it is not controlled or programmed nor can it be changed directly; current is indirectly controlled via programmable voltage (the greater the push, the greater the flow).
Ohm’s law
voltage = current x resistance.
stimulation threshold
the minimum output voltage that consistently achieves capture outside the heart’s refractory period; the pulse width at which the output voltage achieve capture.
when setting voltage:
turn down until you lose stimulation, turn up until consistent, turn up 1.5x that to ensure consistent delivery.
capture:
depolarization of cardiac muscle following an electrical stimulus; considered abnormal because it is out of the normal conduction pathway.