Dysrhythmias and Conduction Problems

initiates an electrical impulse

automaticity

ability to responde to an electrical impulse (injured cells lose excitability)

excitability

ability to transmit an electrical impulse

conductivity

atria and ventricles contract in response to

depolarization

protective mechanism in the heart that prevents multiple, compounded action potentials from occurring

refractory period

cardiac cells are completely unresponsive to stimuli

absolute refractory period

if exposed to stronger electrical stimulus, may depolarize early

relative refractory period

what ion controls muscle fiber contractility

ca+

what ion controls electrical voltage, irritability

K+

what ion plays a role in conduction of cardiac impulses

na+

what ion controls muscle contraction and aids in the absorption of Ca+ and K+

Mg 2+

heart rate is influenced by

metabolic demands

all four chambers relaxed-AV valves open; SL valves shut (A &V filling)

diastole

blood ejected into ventricles (in response to SA node)

atrial systole

late in atrial systole- right before ventricle systole,

gives 15-25 % more volume

atrial kick

blood ejected to body

(AV valves shut; SL valves open)

ventricular systole

measure electrical activity is moving up/down and right/left direction

limb leads

measure electrical activity moving in front/back direction or right/left

chest leads

P wave represents

atrial contraction

shows time it takes from electrical impulse to travel from SA to AV node

PR interval

shows ventricle contraction

QRS complex

getting ready for next beat (repolarization)

T wave

what is the normal duration of the PR interval

0.12 - 0.20 seconds

what is the normal duration of the QRS complex

< 0.12 seconds

what is the normal duration of the QT interval

0.32 - 0.40 seconds

what drugs can cause abnormal/prolonged QT

zofran

amiodarone

erythromycin

methadonw

haldol

how to treat torsade de pointe

treat underlying condition

pacing