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55 Cards in this Set
- Front
- Back
List three causes of sinus bradycardia |
1. acute inferior MI 2. high sympathetic blockade (high spinal) 3. Strong vagal input to the SA node -hypersensitive baroreceptors (Carotid Sinus Syndrone)
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What is the cause of carotid sinus syndrome? |
Hypersensitive baroreceptors due to accumulation of atherosclerotic plaque in the carotid areteries.
Slight neck stimulation will trigger reflex bradycardia. |
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LIst three potential p-wave changes associted with a junctional rhythm |
1. short PR interval 2. no p wave 3. p wave after QRS complex |
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List two characteristics of an idioventricular rhythm |
1. HR 40-60 beats/min 2. Wide QRS |
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List two mechanisms that cause tachycardia |
1. Enhanced automaticity -inflammation -chemical agent (catecholamine, caffiene, nicotine) -mechanical irritation (cardiac catheter)
2. Ischemia giving rise to re-entry pathway |
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What is the most common perioperative dysrhythmia? |
Sinus tachycardia |
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What heart rate is normally seen with sinus tachycardia? |
100-150 bpm |
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List some causes of sinus tachycardia (6) |
Pain (light anesthesia) Anxiety Hypovolemia (hemmorrhagic/shock) Exercise Malignant Hyperthemia Thyrotoxicosis |
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If SVT begins and ends suddenly it is called _____________ |
Paroxysmal SVT (PSVT) |
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Atrial tachycardia due to an ectopic focus is caused by enhanced _________ due to phase _______ depolarization of some focus in the atrium |
enhanced automaticity phase 4 depolaization (caused by "funny" channels) |
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Atrioventricular node re-entrant tachycardia (AVNRT) is caused by _______ pathways in the AV node |
two |
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Describe the pathways involved in atrioventricular node re-entrant tachycardia (AVNRT) |
fast pathway - has slow recovery slow pathway - has fast recovery
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In AVNRT, the re-entrant loop is created through the pathways. ___________ conduction via the slow pathway, and ___________ conduction via the fast pathway. |
anterograde conduction via the slow pathway
retrograde conduction via the fast pathway |
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Are P waves present in AVNRT? |
No |
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List the two causes of atrioventricular re-entrant tachycardia |
1. Wolf - Parkinson - White Syndrome (WPW)
2. Lown-Ganong-Levine Syndrome (LGL) |
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What is the atrial rate seen in atrial flutter? |
250-350 bpm |
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What is the normal conduction ratio seen in atrial flutter? |
2:1 or 3:1 |
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Atrial flutter likely results from re-entry secondary to which conditions (3)? |
Pulmonary embolism Coronary artery disease Valvular disease (mitral stenosis) |
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In junctional tachycardia, the ectopic focus or re-entry pathway is located where? |
The bundle of His |
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Wide complex tachycardia orginates where? |
In the ventricles |
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The normal QRS duration of wide complex tachycardia is: |
>120 ms |
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Premature beats are also known as ____________ |
Extrasystoles |
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If the ventricular conduction pathway is refractory, an atrial preamture beat will result in: |
An abnormal QRS (APB with aberrant ventricular conduction) |
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The difference between an APB and the following sinus beat is normal in duration. Why? |
Because retrograde conduction from the ectopic focus "resets" the SA node. |
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List three characteristics of a PVC |
1. wide QRS > 120 ms 2. Prominant R or S wave 3. May have large, inverted T wave |
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Because a PVC is not conducted back to the SA node, ____________ results |
A compensatory pause (because the SA node is not reset) |
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Ventricular Premature Beats comprise _______ percent of all dysrhythmias during anesthesia |
15 percent |
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If a VPB is closely coupled with the preceeding beat, what can happen? |
R on T phenomenon. Can lead to ventricular tachycardia or ventricular fibrillation. |
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List three areas of the heart where conduction defects are prone to occur: |
1. in and around the SA node (SA exit block) 2. Within the AV node 3. Within the conduction system of the ventricles (bundle branches & fascicles) |
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First degree AV block is characterized by a PR interval longer than ___________ |
0.20 seconds |
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Second degree AV block (Mobitz I) is also known as ___________ |
Wenckebach phenomenon |
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Second degree AV block (Mobitz I) results in what? |
Progressively lengthening PR interval until dropped QRS complex. |
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T/F Mobitz I blocks are at high risk for progressing to complete AV block |
False. - This is more likely to occur with Mobitz II |
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What is the distinguishing characteristic of a Mobitz II block? |
Loss of AV conduction after a constant PR interval (ex. conduction of every other beat) |
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T/F Mobitz II is more serious than Mobitz I |
True - more likely to progress to complete AV block. |
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If the block is below the AV node within the bundle of His, what will the ECG look like? |
Wide QRS |
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What is 3rd degree AV block? |
P waves and QRS complexes at independent frequencies |
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What is Stokes-Adams syndrome? |
Intermittent complete AV block. Fainting followed by initiation of junctional or ventricular escape. |
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In a right bundle branch block an abnormal QRS will often be visible in which EKG leads? |
V1 and V2 |
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What type of QRS complex will be seen in a right bundle branch block? |
rSR' (often two separate peaks) |
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What can cause a right bundle branch block (2)? |
Chronic lung disease Atrial septal defect |
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A left bundle branch block often causes prolonged QRS complex in which leads? |
I and V6 |
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How does the QRS complex change in a left bundle branch block? |
Wide, notched, "rabbit ears" appearance |
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In bundle branch blocks the mean electrical axis shifts _______ the block |
Toward |
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Which type of hemiblock is most common? |
Left anterior fasicular block |
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What EKG changes show up in a LAFB? |
Q wave in lead I S wave in lead III Left axis deviation |
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What EKG changes show up in a RAFB? |
W wave in lead III S wave in lead I Right axis deviation |
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What causes fibrillation |
Asynchronous electrical activity. Often caused by circus movements of multiple impulses. |
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What is the hallmark EKG sign of wolf-parkinson-white syndrome? |
Short PR interval Delta wave - caused by premature depolarization of the ventricular septum. |
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Which type of dysrhythmia does WPW syndrome develop into? |
SVT - atrioventricular reentry tachycardia (AVRT)
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Explain how WPW syndrome develops into AVRT |
Normally conducted impulse re-enters the atria in a retrograde manner and re-activates the atria. |
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What happes to the delta waves when WPW develops into AVRT? |
They dissapear because the re-entrant circuit is now sending impulses to the atria (instead of the ventricular septum) |
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What is the anatomic basis of WPW? |
An abnormal Kent Bundle that transmits impulses from the atria to the ventricular septum. |
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What EKG changes differentiate Lown-Ganong-Levine Syndrome from WPW? |
No delta wave (LGL DOES have short PR interval) |
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Lown-Ganong-Levine Syndrome (LGL) usually results from what? |
Abnormal conduction (bypass) pathway from the atria to the AV bundle. |