automaticity - ability to initiate and maintain electrical rhythm
excitability - ability to respond to electrical stimulus
conductivity - ability to transfer that electrical stimulus to the neighboring cell
contractility - the ability of myocardial cells to shorten and contract in response to an
electrical stimulus
force generated by the contracting myocardium under any given condition
cardiac output - stroke volume X heart rate
amount of blood pumped by each ventricle in liters per minute
stroke volume - the amount of blood ejected with each heart beat
affects by preload, afterload, and contractility
preload - volume of blood in ventricles at the end of diastole
(ventricular filling)
afterload - the amount of resistance the ventricle must overcome to eject the blood out
of the heart
SA node - primary pacemaker of the heart
, initiates electrical impulses at rate of 60-100 bpm
AV node - synchronizes atrial and ventricular activity
picks up slack of SA node at rate of 40-60 bpm
bundle of HIS - located between atria and ventricles
should be the only pathway (if not, indicates conduction issues)
next stop is R and L Bundle Branches
Purkinje fiber - ventricles are finally stimulated to contract
inherent rate of 30-40 bpm (if SA and AV node fail)
depolarization - stimulation
cardiac cell is normally negatively charged
cells receive an electrical stimulus
channels open for Na+ and Ca+ to enter cell
K+ leaves cell, but cell is positively charged
cardiac contraction
repolarization - relaxation
K+ continues to leave cell and Na+ flows into cell
however, Cl- now enters cell
restoration of negative charge
arrhythmias - "dysrhythmias"
disorders of the electrical impulse within the heart that causes disturbances
named according to site of origin of impulse and mechanism of conduction
12-lead EKG - uses 10 electrodes (one of each limb, 6 on chest)
produces 12 difference waveforms
gives us full picture of what is going on in heart
continuous telemetry monitoing - uses 5 leads
typically seen in hospital setting
leads in continuous telemetry - LA, RA, LL, RL, anywhere V1-V6
smoke over fire, clouds over grass, poop in the middle
continuous telemetry monitoring indications - any ICU patient
post-cardiac intervention
post-acute MI
specific medications
cardiac patients being actively treated
EKG - graphic recording of the electrical activity of the heart
L-R is time
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