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Phys2 Intro Arrhyth

QuestionAnswer
arrhythmia an abnormality of impulse initiation, impulse conduction, or both.
Types of impulse INITIATION arrhythmias 1.Normal Automaticity (associated w/ normal automatic pacemaker). 2.Abnormal Automaticity (associated w/ non-pacemaker cells that develop automaticity). 3.Triggered activity (Em oscillations triggering an AP)
impulse CONDUCTION arrhythmias Associated w/ a delay or block of conductance. Ex: 1.AV delay. 2.Block and re-entry.
Impulse initiation arrhythmia: Normal pacemakers: latent pacemakers 1.Atrial conduction: 60-80 bpm. 2.AV node: 40-60 bpm. 3.Ventricular Purkinje: 20-40 bpm. **SA node is the normal pacemaker (60-100 bpm)
Impulse initiation arrhythmia: Normal pacemakers: abnormal Sinus rhythm from ANS? Sinus Bradycardia < 60-100 bpm < Sinus Tachycardia. **Usually in response to metabolic disturbances.
Impulse initiation arrhythmia: Normal pacemakers: Sinus Arrhythmia? Inspiration: Accelerates HR. Expiration: Decelerates HR. **this is a normal cyclic rhythm that is due to stretch receptors activating the ANS.
How do latent pacemakers cause impulse initiation arrhythmias? 1.They become enhanced. 2.SA node becomes depressed/damaged. 3.conduction block. **These emerge via Inc parasymp tone, Ischemia, drug toxicities, Electrolyte disturbances.
Impulse initiation arrhythmia: Abnormal Automaticity Tissue becoming automatic due to: 1.Ischemia. 2.Infarction. 3.Hypoxia. 4.acidosis.
Can arrhythmias generated from abnormal automaticity be overdrive suppressed? NO, the body doesn't have any physiologic control over them since they are damaged. They compete with the SA node.
Impulse initiation arrhythmia: Triggered activity 1.Early afterdepolarizations (EAD): occur before phase 3 repolarization. 2.Delayed Afterdepolarizations (DAD): occur after phase 3 repolarization **Afterdepolarization is an oscillation of Em following the upstroke of an AP
What ion could be responsible for EADs and DADs? Ca2+
Impulse conduction arrhythmia: conduction block: 1st degree block Prolonged P-R interval (>0.2sec), but every impulse gets through the AV node.
Is a bundle branch block considered a 1st degree block? NO, despite the fact that it is included in the P-R interval, it would cause a wide QRS if it were blocked.
Impulse conduction arrhythmia: conduction block: 2nd degree block **Not ALL impulses get through AV node 1.Wenckebach (Mobitz Type 1): Progressive prolongation thru AV node w/ eventual dropped beat. 2.Mobitz Type II: Dropped beats without P-R interval prolongation (VERY BAD)
Impulse conduction arrhythmia: conduction block: 2nd degree block: Mobitz Type II P wave to QRS ratios Can be seen with 2:1 or 3:1 Pwave:QRS
Impulse conduction arrhythmia: conduction block: 3rd degree block COMPLETE block through the AV node. P wave doesn't conduct through the node. **Must relay on a latent pacemaker so look for a decreased HR.
What could contribute to AV node blockage? 1.Inc Vagal tone (M receptors dec AV conduction). 2.Ca2+ Channel blockers. 3.Beta-Blockers (Symp can't activate B1 receptors). 4.Digitalis. 5.Hyperkalemia
Impulse conduction arrhythmia: Re-entry arrhythmia where the signal doesnt die out, it recirculates and re-excites tissue. **can be ordered or random, anatomical or functional
In what conditions would re-entry be necessary? 1.Unidirectional block. 2.Slowed conduction (over alternative pathways). 3.Re-excitation of tissue proximal to the block (refractory period of proximal tissue must be shorter than propagation around the block).
Wolf-Parkinson-White syndrome (WPW) Pt has an alternative pathway to transmit the signal from the atria to the ventricles that is faster than the AV node. **This causes pre-excitation
Why do you see Atrial tachycardia with WPW? RE-ENTRY!! After the impulse travels down the AV node, the ventricular contraction (depolarization) then sends the impulse back up the accessory pathway to depolarize the atria.
Supraventricular tachycardia Is due to the circus rhythm seen in WPW patients with re-entry.
How does WPW pre-excitation effect the EKG? 1.Shortens the P-R Interval. 2.Widens the QRS **DELTA WAVE: represents the early excitation of the ventricles, widening the QRS.
How does WPW re-entry atrioventricular tachycardia effect the EKG? 1.Orthodromic (Anterograde down AV node): Creates RETROGRADE P Waves immediately after QRS. 2.Antidromic (retrograde up AV node): Very wide QRS w/ retrograde P wave following.
Created by: WeeG