Term
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Definition
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Term
| What are the 6Hs that are common causes of all dysrhythmias? |
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Definition
1. hypoxia
2. hypo/hypervolemia
3. hypo/hyperelectrolytes
4. hypo/hyperthermia
5. hypo/hyperglycemia
6. hydorgen ion (acidosis/alkalosis) |
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Term
| What are the 6Ts that are common causes of all dysrhythmias? |
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Definition
1. Tamponade, cardiac
2. Thrombus, coronary (MI)
3. Thrombus, pleural (PE)
4. Tablet intoxication
5. Trauma
6. Tension pneumothorax |
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Term
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Definition
| Pulseless Electrical Activity (PEA) is when there is a dissociation between electrical activity detected by an EKG and the patient's assessment. E.g. patient is pulseless but showing a rhythm. |
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Term
| What are the conditions that cause PEA? |
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Definition
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Term
| Define depolarization, repolarization, excitability, conductivity, and contractility |
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Definition
Depolarization: cardiac cell membrane potential changes from negatiive (-90mV) to positive (+20mV)
Repolarization: return of cells back to restating state (-90mV)
Excitability: Ability of cells to depolarize. Most heart cells can do this.
Conductivity: cells depolarize AND stimulate adjacent cells by passing on the impulse (conducting)
Contractility: ability of excitable cells to mechanically contract/shorten |
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Term
| Explain the All-or-nothing phenomenon |
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Definition
| The excitability, conductivity, and contractility properties of heart cells allow the heart to act as an organized pump. Each heart cell is NOT innervated by the CNS separately so once one cell is stimulated, ALL cells are stimulated. If an impulse cannot stimluate one cell then nothing will happen - there is no gradient of stimulation with heart cells |
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Term
| What cells of the heart possess automaticity? |
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Definition
| cells of the SA node, AV node, and Purkinje fibers |
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Term
| What is unique about cells of the SA node, the AV node, and the Purkinje fibers? |
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Definition
| These cells possesss automaticity/autorhythmicity and DO NOT require stimualtion by adjacent cells or the CNS to create an impulse. These cells set the rhythm of the heart |
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Term
| Describe the conduction of an action potential through cardiac cells (non-autorhymic cells). |
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Definition
**numbered to match with the diagram on study packet
0. Rapid depolarization: massive influx of Na and Ca into the cell along with slow efflux of K from the cell
1. Early Repolarization: Na channels are becoming inactivated; Ca channels stay open; K continues to leave the cell
2. Plateau: Na channels complete inactivated; Ca channels remain open.
3. Repolarization: Ca channels close; K channels open allowing an influx of K back into the cell
4. Resting Membrane Potential: cell membrane more permeable to K, allowing the cells to maintain it's negative resting state (-90mV) |
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Term
| Describe the conduction of action potentials by the Pacemaker cells of the SA node, AV node, and Purkinje fibers (autorhytmic cells) |
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Definition
numbered to match with the diagram on the study packet
0: Depolarization: slow Ca channels open; K channels closed
3: Repolarization: slow Ca channels close, and delayed K channels open
4. Diastolic Depolarization: secondary to gradual increase in Ca, Na and gradual decrease in intracelluar K via leaky membrane permeability |
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Term
| Compare/Contrast pacemaker cells and other cardiac cells |
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Definition
1. pacemaker cells have a higher resting membrane of -65mV (can depolarize faster)
2. pacemaker cells have a leaky membrane permeabilit that allows for slow influx of Na, Ca and efflux of K |
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Term
| What should you do if PEA is suspected? |
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Definition
1. Assess patient!!!!
2. Assessment and documentation of the electrical function of the patient's heart |
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Term
| PEA is associated with what dysrhythmias? |
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Definition
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Term
| What is the inherent autorhymicity rate of the SA node? The AV node? The Purkinje fibers |
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Definition
SA node: 60-100bpm
AV node: 40-60bpm
Purkinje Fibers: 20-40bpm |
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Term
| Describe the conduction pathway of an impulse |
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Definition
1. Impulse is initated by the SA node
2. Transmission to atrial tissue
Atrial Contraction
4. Impulse to AV node
5. Common Bundle of His
6. L/R Bundle branches
7. Purkinje Fibers
Ventricular contraction |
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Term
| Relate the EKG waveform with the corresponding activity of the heart |
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Definition
P wave: atrial depolarization
PR interval: time it takes impulse to travel from SA node to AV node, conduct through AV node, spread down bundle of His and bundle branches
QRS complex: ventricular deplolarization
QT interval: time it takes for ventricles to depolarize and repolarize
T wave: ventricular repolarization
ST segment: isoelectric line between QRS and T. |
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Term
| What is significant about the ST segment in EKGs? |
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Definition
| If ST segment is not an isoelectric line - can use to determine extent of cardiac ischemia/injury using a 12-lead EKG |
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Term
| What is the absolute refractory period and when does it occur? |
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Definition
-from beg of QRS complex to halfway through T wave (before downward slope)
-During this period, a stimulus is unlikely to cause depoliarization as most cells of the heart are depolarized |
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Term
| What is the relative refractory period and when does it occur? |
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Definition
-downslope of T wave
-During the RRP: some cardiac cells are depolarized and some are repolarized. This makes the heart vulnerable to internal and external stimuli and can develop dyrhythmias (e.g. Vfib) |
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Term
| What is the R on T phenomenon? |
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Definition
| When there is internal or external stimulation of the cardiac cells during the downslope of the T wave (ventricular repolarization) |
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Term
| What are some examples of internal/external stimuli that can cause an R on T pheomenon? |
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Definition
Internal: early beats from ventricle (PVCs)
External: pacemaker malfunction, external chest impact from sports |
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Term
| What two factors impact the electrical signal we detect from the heart? |
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Definition
1. direction for the electrical current
2. placement of electrodes |
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Term
| What are the unipolar leads in an EKG? |
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Definition
AVR: right arm is positive
AVL: left arm positive
AFL: left leg positive |
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Term
| What are the bipolar leads of an EKG? |
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Definition
Lead I: right arm electrode is made negative, L arm electrode positive; Detects impulses from R-L across the chest
Lead II: right arm is negative and left leg is positive; Detects impulses that travel across the body from chest to leg
Lead III: left arm negative and left leg positive; Detects impulses that travel from the upper -lower body. |
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Term
| Describe the correct placement of the Pericardial leads (6) |
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Definition
V1: 4th ICS, right sternal border
V2: 4th ICS, left sternal border
V3: between V2 and V4
V4: 5th ICS, midclavicular line
V5: between V4 and V6
V6: 5th ICS, midaxillary line |
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Term
| What duration is represented by each small box on an EKG strip? Big box? 5 big boxes? |
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Definition
small box: 0.04s or 40ms
big box: .2s or 200ms
5 big boxes: 1s or 1000ms |
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Term
| What are the 6 steps of the Rhythm analysis Procedure? |
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Definition
1. Determine HR
2. Determine Rhythm (regular/irregular)
3. Determine P wave morphology + A:V ratio
4. Determine PR interval duration(should be 120-200ms or .12-.2s)
5. Determine QRS morphology and duration (should be <120ms or <.12s)
6. Determine QT interval (should be <1/2R-R) |
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Term
| When is sinus rhythm NOT normal? What are the correct actions to take in this event? |
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Definition
When a person has a high baseline HR -can be "relative bradycardia" in this case. It is dangerous because CO may be inadequate at a lower HR
-Tx: pacing and positive chronotrophs while determining etiology |
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Term
| What is the major concern for someone suffering from bradycardia or relative bradycardia? |
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Definition
| Decreased cardiac output may not be enough to perfuse vital organs (brain, heart) |
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Term
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Definition
| blocks parasympathetic stimulation to increase rate of SA node depolarization |
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Term
| After after giving atropine to a patient in sinus bradycardia, you do not see the desired increase in HR. Why is this so? |
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Definition
| If etiology of bradycardia is not excessive parasympathetic stimulation then atropine will not have a great effect |
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Term
| What are the pros/cons of transcutaneous pacing? |
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Definition
Pros: no IV or ET tube required.
Cons: painful - must give analgesia or sedate |
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Term
| Why are the signs and symptoms of bradycardia and tachycardia similar? |
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Definition
| Both conditions result in decrease cardiac output. Think CO = HR x SV. In brady, HR is lower so CO is lower. In tachy, SV is low because a faster HR doesn't allow the heart to fill completely thus decreasing SV and decreasing CO. |
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Term
| At what point does Sinus tachycardia become dangerous? |
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Definition
| rates above 120bpm because impaired filling (diastole) results in decreased coronary artery perfusion. If HR > 150bpm with serious s/s: cardiovert. |
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Term
| What are the three major concerns regarding atrial fibrillation? |
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Definition
1. Control HR to prevent serious signs and symptoms
2. Prevent Clot Formation: increased blood stasis due to unorganized contraction of the atria. Clots can start to form at 24-48 hours and can be ejected into the coronary arteries, brain, liver, etc.
3. Loss of cardiac output which in the long run can lead to multi-system organ dysfunction related to poor end-organ perfusion |
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Term
| Name the common antiarrhythmic drugs |
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Definition
1. Amiodarone
2. Sotalol
3. Rlecainide
4. Propafenone
5. Dofetilide
6. Quinidine
7. Procainamide |
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Term
| What is the major difference in EKG tracing between Atrial fibrilliation and atrial flutter? |
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Definition
| Presence of identifiable P waves |
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Term
| What does the appearance of a different QRS complex following a PAC indicate? |
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Definition
| impulse has depplarized the heart in an aberrant fashion - PAC with aberrant conduction |
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Term
| Explain the difference between Junctional rhythms (high, mid, low) on an EKG tracing and the corresponding caridiac events. |
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Definition
High JER: atrial depolarization occurs before ventricular depolarization but in a retrograde fashion UPSIDE DOWN P WAVE) because being stimulated by AV node cells not SA node
Mid JER: Ventricular + atrial contxn occur at the same time => NO P WAVE
Low JER: atrial depolarization occurs after QRS => UPSIDEDOWN P WAVE after QRS |
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Term
| How can you tell the difference between Afibrillation and Mid Junctional Escape Rhythm? |
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Definition
*both have no p waves!
BUT afib is irregularly irregular and mid JER is regular. Looks like sinus tachy w/o P waves |
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Term
| Why might atropine not be effective for treatment of bradycardia symptoms related to Junctional Escape Rhythms |
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Definition
| Atropine works on parasympathetic stimulation but parasympathetic fibers only innervate the atria, above the AV nodal area. In JER, the SA node is most likely damaged forcing the AV node cells to take over pacing of the heart |
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Term
| How does synchronized cardioversion work? |
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Definition
| Spontaneous depolarization of a critical mass of cardiac cells resulting in a temporary absence of rhythm that (hopefully) allows the pt's normal conduction rhythm to resume. |
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Term
| When is the current delivered in synchronized cardioversion? Why? |
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Definition
| Electric current is administered at the R wave when most of the cardiac cells are already depolarized. It prevents the current from occuring during the relative refractory period as this may result in R on T phenomenon and put the pt in a letal ventricular rhythm |
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Term
| What are common vagal maneuvers? |
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Definition
1. Tell pt to bear down as if having a BM
2. take a deep breath, hold it,
3. cough & gag
4. carotid sinus massage -ONLY ADVANCED PRACTITIONERS
5. digital rectal stimluation
6. submerging face in ice water |
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Term
| How does Adenosine work to help diagnose SVTs? |
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Definition
cardiac lycoside
-causes temp puase in ventricular activity to help visualize atrial activity that is contributing to SVT
-6 second half life |
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Term
| What symptoms should be monitored in pts receiving adenosine? |
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Definition
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Term
| Why is the use of Amiodarone/Lidocaine contraindicated in the treatment of ventricular escape rhythms? |
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Definition
| These drugs will suppress ventricular rhythm and may completely stop impulses. Agonal rhythms result as a last line of defense (failure of SA/AV node pacing) so must preserve rhythm. Treatment should include pacing and Dopmine/epinephrine infusions |
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Term
| How can you determine the difference between a PAC and a PVC? |
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Definition
presence of P wave in front of each premature QRS.
-if P wave present: PAC
QRS duration
-if QRS narrow (<120ms, .12s): PAC
-if QRS wide (>120ms, .12s): PVC |
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Term
| What is the general treatment regiment for PEA? |
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Definition
1. CPR if no pulse
2. Epi q3-5min IVP and vasopressin IVP one time
3. Atropine IVP q4-5min
**Consider underlying cause!!! |
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Term
| Why is transcutaneous pacing the preferred first step for pts with complete heart block? |
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Definition
| disscociation between atrioventricular conduction means increasing SA node activity would not affect ventrictular contraction |
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Term
| What is the difference between type I and type II second degree heart block? |
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Definition
Type I (Wenckebach): progressively proglonged PR intervals
Type II: consistently long PRI and some P w/ no corresponding QRS |
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Term
| In Complete Heart Block, what do the different QRS complexes tell us? |
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Definition
Wide QRS (>120ms, .12s): ventricular pacing
Narrow QRS (<120ms, .12s): junctional pacing |
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