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74 Cards in this Set
- Front
- Back
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Sinoatrial (SA) node
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a small cluster of cells located in the upper right atrium; t is the pacemaker ofthe heart; normal or inherent rate is 60-100 beats per minute
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Internodal Pathways
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Impulses sent by the SA node travel through the arial muscle fibers via he intra-atrial pathways; allows for simultaneous depolarization and contraction of the atria
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Atrioventricular (AV) node
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located in the lower portion of the right atria, receives impulse from the SA node; delays te conductionto allow for the atria to contract, then conducts to the ventricle
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Bundle of His
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lies in the upper part of the intraventricular septum and connects the AV node with the bundle branches; the AV node and Bundle of His are collectively known as he Junctional Area; normal or inherent rate (40-60); back up system for the SA node
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Right Bundle Branch
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arise from the Bundle of His and travel down the left side of the septum; branches off into towo sections because the leftventricle is much larger than the right ventricle
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Left bundle branches
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arise from the Bundle of His and travel down the leftside of the septum; branches off into two sections because of the left ventricle is much larger than the right ventricle
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Purkinje Fibers
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smaller branches of the bundles branches; spread throughout the myocardium and terminate there; normal or inherent rate is 20-40
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Automaticity
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the ability to act as an impulse, initiating electrical activity and spontaneous depolarization (this is he most important difference between cardiac and skeletal muscle cells)
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excitability
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the ability to respond to a stimulation and initiate an impulse
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conductivity
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the ability to transmit an impulse that has been initiated and passes along cell membranes
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contractility
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the abilityof a muscle fiber to shorten in response to a stimulus
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refractoriness
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the inability of a muscle fiber to respond to a stimulus during an interval following contraction
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Absolute Refractory Period (ARP)
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time interval, when no matter how strong the stimulus, a cardiac cell cannot be depolarized. Measured from the beginningof the QRS complex to themiddle of the T wave
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Relative Refractory Period (RRP)
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time interval, when given only a stronger than normal stimulus, a cardiac cell may depolarize. Known as the Vulnerable period. Measured from the middle of the T wave to the end of the T wave
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4 things provided by an EKG
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1. Conduction disturbances
2. Cardiac muscle mass 3. Ischemia, injury, or infarction 4. DOES NOT PROVIDE INFORMATION ON THE MECHANICAL CONTRACTION/PUMPING ACTION |
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P wave
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represents atrial depolarization
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PR interval
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represents time it takes for original impulse to pass from SA node through the atrial depolarization. Normal is 0.12-0.2 seconds
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QRS complex
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represents ventricular depolarization. Measured from beginning of Q wave to the end of the S wave (if a Q,R, or S wave is absent, the QRS is measured from the beginning to the end of the remaining waves. Normal QRS duration : 0.06 - 0.1 seconds
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T wave
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represents ventricular repolarization
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ST segment
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represents time interval btw completion ofdepolarization and the beginning of repolarization of the ventricles. Normally, this segment is isoelectric. an elevation or depression of this segment indicates an abnormality in the onset of recovery of the ventricular muscle, usually because of myocardial injury/ischemia
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ST ischemia is identified by
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ST segment dropping below the isoelectric line
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ST injury is identified by the
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ST segment elevating above he isoelectric line
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QT interval
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represents the total period of time required for depolarization and repolarization of the ventricles. Measured from the beginning of the QRS totheend of the T wave. Normal time interval is less than 0.4 seconds. Some factors that lengthn the QT interval include: drug toxicity (amiodarone, antibiotics, some CNS drugs, some chemotherapy drugs), electrolyte imbalances (hypokalemia, hypomagnesemia, hypocalcemia) and cocaine use. Genetic causes. Prolonging the QT interval ca lead to lethal dysrhythmias
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Sinus rhythm
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one P wave for each QRS complex. PR interval at least 0.12 seconds Rate 60-100
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Sinus Brady
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one p wave for each QRS complex. PR interval at least 0.12 sconds
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treatment for sinus brady
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usually none. Atropine or pacing if symptomatic
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Sinus tachy
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one p wave for each QRS complex. PR interval at least 0.12 seconds. rate 101-150
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Treatment for sinus tachy
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treat cause
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SInus arrhythmia
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one P wave for each QRS complex. PR interval at least 0.12 seconds. Irregular rhythm. Rate increases during inspiration and decreases with expiration.
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Treatent for sinus arrest
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discontinue digoxin. Atropine or pacing if symptomatic
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Premature beat
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beat that comes in early P-P or R-R inerval shorter than normal
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escape
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normal pacer fails to fire so a lower site initiates the impulse. R-R interval longer than noral (QRS complex is late). protective mechanism
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Premature atrial contraction (PAC)
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P wave early and looks different. PR interval within normal limits but may be different than sinus PR interval. Must have underlying rhythm.
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Treatment for PAC
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usually none. If occurs in presence of heart disease - use digoxin, quinidine, procainamide, beta, and channel blockers
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Atrial Tachycardia
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one p wave for every QRS complex, however, may not be able to see P wave becasue in preceding QRS. PR constant. QRS normal rhythm regular. Rate 150-250
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Treatment for Atrial Tachycardia
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If pt hemodynamally stable: Vagal. adenosine. calcium channel blockers/beta blockers. If hemodynamically unstable: Sedate and cardiovert
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Atrial flutter
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flutter waves. atrial rate 250-350
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Treatment for atrial flutter
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diltiazem
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atrial fibrillation
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fibrillaory wave instead of p waves. atrial rate greater than 350 however unable to count the atrial rate
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treatment for a fib
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amiodarone, diltiazem, cardioversio. anticoagulation
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premature junctional contraction
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impulse originates in AV junction. P wave may occur before, during or after QRS complex. If p wave occurs before QRS the PR interval will be SHORTER than normal (less than 0.12 seconds). P wave may change configuration of QRS complex if it occurs during or just after QRS. THis is notan underlying rhythm
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Junctional rhythm
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P wave before, during or after each QRS complex or no P wave at all. If P wave occurse before QRS, PR interval shorter han 0.12 seconds. QRS usaly normal. P waves inverted in Lead II. Rate 40-60. This is an underlying rhythm.
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Treatment for junctional rhythm
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hold digoxin, atropine if symptomatic
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Accelerated junctional rhythm
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same as junctiona rhythm except rate between 61-100
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Treatment for accelerated junctional rhythm
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hold digoxin
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Junctional Tachycardia
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same as junctional rhythm except rate greater than 100.
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Treatment for junctional tachycardia
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Ca Channel Blockers, Beta Blockers, adenosine, vagal maneuvers
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Junctional escape beat
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compensatory mechanism when sinus rate slows, arrests, or is blocked. Same features as PJC except ocurrs later rather than earlier than expected.
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Treatment of junctional escape beat
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Treat cause of slowed rhythm
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Supraventricular tachycardia (SVT)
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a catch all term for any tachycardic rhythm that occurs above the ventricles. May see this used when cannot distinguish between atrial tach and junctional tach because P waves are not definable.
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Treatment of SVT
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Stable: adenosine, vagal, calcim channel blockers, beta blockers
Unstable: sedate - cardiovert |
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Premature ventricular contraction (PVC)
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ectopic impulse originating in the ventricle that occurs earlier than QRS complex is expected. QRS looks wide and bizarre, greater than 0.1 seconds. Usually don't see P wave. Generally have compensatory pause. Can be unifocal (all PVC's look the same) or multifocal (PVC's look different). Can have patterning:
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bigeminity
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every other beat is a PVC
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trigeminy
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every third beat is a PVC
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quadrageminy
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every fourth beat is a PVC
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Treatment for PVC
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usually none. AMiodarone or lidocaine if pt is symptomatic
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Idioventricular rhythm
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regular venticular rhytm. rate 20-40. wide bizarre 0.12 seconds or greater
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Treatment idioventricular rhythm
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pacing
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Accelerated ideoventricular rhythm
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regular ventricular rhythm. rate 40-100. wide, bizarre 0.12 seconds or greater. T wave in opposite direction. No P waves
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Treatment for accelerated ideoventricular rhythm
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usually none. watch for slowing rhythm
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Ventricular tachycardia (Vtach)
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QRS complexes wide and bizarre, greater 0.10 seconds. Rhythm regular. Rate greater than 100
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Treatmentfor V tach
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Hemodynamically stable: amiodarone lidocaine
if unstable: cardiovert Pulseless and unconscious: CPR & defibrillate |
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Torsades de points
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multidirectional type of ventricular tachycardia
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Ventricular fibrilation
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rapid irregular undulation varying contour and amplitude. Patient cannot maintain a pulse or BP because there is no cardiac output
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First degree heart block
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abnormally long PR interval and only occurs in a sinus rhythm. Always identify the underlying rhythm ie sinus rhythm with a first degree heart block. Check mediation list
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Second degree type I Wenkebach
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Th PR intervals are variable. Patterne progressive lengthening of the PR interval
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treatment for Second degree type I Wenkebach
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usually none. atropine or pacing if symptomatic from low ventricular rate. STOP digoxin
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Second degree type II (Mobitz)
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an unstble rhthym that can deteriorate to complete heart block. There may be two or more P waves for each QRS. THe PR interval may be normal or long but remains the same for conducted beats. Constant. QRS width may be normal or wide. The widh has to do where the block occurs not the rhythm.
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Treatment for Second degree type 2 mobitz
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pacing is preferred
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3rd degree (complete heart block)
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occurs when the AV junction (AV node and bundle of His) are completely blocked and theinherent rates kick in. The atrial rate will be faster than the ventricular rate. The PR intervals will be variable with no pattern. The QRSs will be regular because the impulse is coming from the bundle branches/venricles. Many tmes some of he P waves are hidden in the QRSs and T waves and are not visible. The width of the QRSs may vary depending on he level of block. The slow rate cause the symptoms.
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Failure to capture
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THe pacemaker delivers the pacing stimulus at the appropriate timing intervals but the expected paced QRS complex does not follow the pacing spike
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treatment for Failure to capture
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inc voltage
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Oversensing
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The pacemaker is inappropriately inhibited from firing because it detects electrical signals other than the intended R wave
Treatment is decreasing sensitivity |
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Undersensing
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failure of the pacemaker to sense the R wave. The pacemaker emits inappropriately timed impulses. Recognized by pacing spikes that follow too closely behind intrinsic QRS complexes. Pacemaker fires to early after the patents own beat. Pacemaker looks as if it fired early. Treatment is to increase sensitivity.
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