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Cardiac Dysrhythmias and Conduction Disorders
|What 3 things can cause Dysrhythmias?
|1. Abnormal Automaticity. 2. Triggered activity due to problems with refractory phase. 3. Re-entry (circus) pathways of electrical conduction.
|What are 2 types of abnormal sinus rhythm dysrhythmias?
|Tachycardia and Bradycardia
|Tachycardias are usually due to what?
|Increased body temperature, cardiac toxicity, or increased sympathetic discharge on myocardium.
|Bradycardias frequently occur as a result of what?
|Excessive vagal stimulation (George Washington's vasovagal syncope)
|When does an SA node block occur? What happens?
|when sinus node impulse can't propagate. Ventricles still pick up some rhythm, usually from the AV node. (example: disease or electrocution)
|What are worse- problems with the atria or problems with the ventricles?
|Problems with the ventricles are worse.
|What is an incomplete AV node blockade? Explain 1st degree and 2nd degree AV node blockage:
|Transmission through the AV node is delayed or occasionally blocked. 1st degree: transmission is delayed. 2nd degree: transmission is delayed and sometimes blocked.
|What is complete (3rd degree) AV node blockade?
|Transmission through the AV node is completely blocked. Timing of the atria is completely dissociated from the timing of the ventricles.
|What is the main problem with a complete AV node blockade?
|No direct communication between the top of the heart and bottom of the heart.
|What can be involved with premature contractions?
|Ectopic pacemakers, atria, AV node (both included as supraventricular tachycardias) and ventricles.
|What is an ectopic pacemaker?
|Something other than the SA node is setting pace/beat.
|The myocardium is more or less active when it is damaged?
|More active. "Sparkler/lit fuse"
|What is the most common cause of premature contractions?
|Ischemia due to atherosclerosis.
|What can cause premature contractions?
|Ischemia, atherosclerotic disease, or toxicity associated with drugs, nicotine or caffeine.
|Premature contractions occur quite frequently where in people?
|In the atria of normal people.
|Premature contractions are more serious in the __________________ and can lead to ______________________.
|Ventricles; Ventricular fibrillation.
|Ectopic pacemakers in the ________________ are more serious and symptomatic.
|Paroxysmal Tachycardias: Cause? what happens? Treatment?
|1) Usually due to an ectopic pacemaker, which sets rhythm for rest of heart. 2) heart undergoes bursts of paroxysmal activity. 3) Can be halted by vagal stimulation producing AV node block. (pretend to poop)
|What is paroxysmal activity?
|Temporary bouts of tachycardia.
|What is the most serious dysrhythmia?
|What is Vtach due to?
|Frequently due to ischemic disease, electrical shock. Often involves re-entry. Emergent and life threatening.
|What is the problem of re-entry of impulses in the heart?
|Circus Pathway (circle)... never enters part where everything stops and rests. A normal impulse dies off because tissue just fired and becomes refractory. However, impulse is delayed or blocked and tissue is not refractory - will be impulse generator.
|Aspects of Atrial Fibrillation:
|Not nearly as dangerous as VF. Ventricles can often maintain their own rhythm. Blood passively leaks into ventricles, especially as the atria tend to quiver and squeeze blood into the ventricles.
|Dysrhythmias are abnormal cardiac rhythms that occur because of either ________________ or __________________.
|Abnormal impulse generation (automaticity) or abnormal impulse conduction which can lead to "re-entry" of the impulse.
|Antidysrhythmics act by _________________ or __________?
|Suppressing abnormal impulses or altering a re-entry circuit (slowing it). They slow things down.
|Many antidysrhythmic drugs can make things worse. What is this called?
|What does it mean that drugs have effects which are state-dependent? Is this good or bad?
|Many antidysrhythmic drugs block only activated or inactivated channels. This means drugs tend to affect only very active/abnormal tissues and not affect the tissues performing normally. This is GOOD.