Arrythmias

Question	Answer
Arrhythmia	an abnormality of impulse initiation, impulse conduction or both
Normal automaticity	arrhythmias associated with normal automatic pacemakers
abnormal automaticity	arrhythmias associated with non pacemaker cells that develop automaticity
triggered activity	oscillations in membrane potential that trigger an action potential
Normal SAN pacemaker	60-100 bpm
Atrial conduction fibers	60-80 bpm
AV junction	40-60
Ventricular Purkinje	20-40
True normal pacemaker	SA node
What makes the latent pacemakers emerge?	High parasympathetic tone High catecholamine concentration hypoxemia ischemia electrolyte distrbances drug toxicities
Abnormal automaticity	tissue that is not normally automatic becomes automatic; often cannot be overdrive suppressed
Triggered activity	early afterdepolarizations delayed afterdepolarizations
EAD	occur before full phase 3 repolarization
DAD	occur after phase 3 repolarizations
Digoxin	Blocks Na/K pump. Dig toxicity will lead to DADs and has increase in intracellular Na+ which will inhibit Na/Ca pump leading to increased Ca in the SR.
1st degree block	every pulse conducts
2nd degree block	some, not all pulses conduct
3rd degree block	no pulses conduct
2nd degree type I	Wenkebach; progressive prolongation thru the av node with an eventual dropped beat
2nd degree type II	Mobitz II; dropped beats without the prolongation of the PR interval
2:1 Morbitz block	dropping every other beat. Every other P wave has a QRS
3:1 Morbitz	3 P's for every QRS
What are some of the mechanisms that could contribute to block in the AV node?	block Ca+ channel Increase vagal outflow Digitalis Hyperkalemia Adenosine
Re-entry	circus movement; an impulse that does not die out, it instead continues to circulate and re-excite tissue
Conditions that are necessary for re-entry to occur.	1. unidirectional block, or transient block 2. slowed conduction over an alternate pathway 3. Proximal re-excitation
Re-entry may be promoted by ______________	things that slow conduction velocity, shorten the refractory period or a combination of both
Examples of random re-entry	Ventricular Fibrillation
Is re-entry ordered or random?	both
Re-entry may accur around _______ or it may be ______________.	anatomical;functional
Classic example of re-entry	wolff-parkinson-white syndrome
WPW	pre-excitation; has an accessory pathway; result is supraventricular tachycardia
Pre-excitation shows what kind of wave?	Delta wave
3 Examples of re-entry	V-Fib A-Fib WPW

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