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Medicine II > Dysrhythmias and Conduction Disorders > Flashcards

Dysrhythmias and Conduction Disorders Flashcards

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1
Q

What is electrocardiology?

A

ability to generate spontaneous action potentials, aka “pacemaker ability”

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2
Q

In the resting state, cardiac cells are _______.

A

electrically polarized (insides are neg charged with respect to their outsides)

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3
Q

Membrane ion channels open and close using _____ to transfer ions between the intracellular and extracellular compartment.

A

pumps (ex: Na+, K+, Ca2+)

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4
Q

What can spontaneously depolarize and are the electrical power source of the heart?

A

pacemaker cells

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5
Q

What are contractile cells?

A

they carry out the actual contraction but are also capable of transmitting the action potential (automaticity), at a much lower speed than the conduction cells

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5
Q

What are conduction cells?

A

form the fiber networks inside the myocardium and disseminate the action potential, they have no contractile function

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6
Q

What acts as the normal pacemaker of the heart?

A

SA node

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7
Q

What is the SA node?

A

oval structure located near the entrance of the SVC in the right atrium, pacemaker cell that spontaneously and repeatedly generates electrical impulses and does not have a resting phase

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8
Q

SAN action potential is mediated by

A

calcium ion currents (node= slow response tissue)

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9
Q

Parasympathetic innervation (vagus nerve) _____ conduction.

A

slows

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10
Q

Sympathetic innervation (spinal cord) ____ conduction.

A

speeds

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11
Q

How is the rate of spontaneous depolarization in the SAN modified?

A

by altering electrolyte exchange or input from the autonomic nervous system

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12
Q

What are cardiac agents for the SA node?

A

calcium channel blockers, digoxin, beta blockers

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13
Q

What are noncardiac agents for the SA node?

A

parasympathomimetic agents, sympatholytic drugs

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14
Q

Tell me about calcium channel blockers.

A

block influx of calcium, reduces upstroke of AP

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15
Q

Tell me about digoxin.

A

increase parasympathetic effects

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16
Q

Tell me about beta blockers.

A

offsets sympathetic inputs

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17
Q

What are examples of parasympathomimetic agents?

A

Betachol, Pilocarpine, Acetylcholinesterase inhibitors

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18
Q

What are examples of sympatholytic drugs?

A

Methyldopa clonidine, Lithium, Ivabradine

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19
Q

What modulates the response between the atrium and the ventricle by impeding impulse conduction?

A

AV node

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20
Q

What is the AV node?

A

conducting cell located at boundary between atria and ventricles, has no automaticity, excited only by pulses that propagate through it

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21
Q

In a normal heart, the AVN is the only ________ from the atria to the ventricles.

A

conducting path

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22
Q

The AV node modulates ventricular response by _____ impulse conduction. It generates a slow action potential that is mediated by ___ currents (node= slow response tissue).

A

impeding, calcium

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23
Q

The ____ node DOES NOT have automaticity while the ____ cells surrounding it do possess it.

A

AV, pacemaker

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24
What are the cardiac agents of the AV node?
calcium channel blockers, digoxin, Beta blockers, adenosine
25
Tell me about adenosine.
transiently inc potassium conduction and dec calcium influx
26
What are the noncardiac agents of the AV node?
carotid sinus massage, valsalva maneuver
27
What is the carotid sinus massage?
5 secs of firm manual pressure applied on carotid sinus area, left side is more likely to act on AV node whereas right side acts on SAN
28
What is the Valsalva maneuver?
bearing down, coughing, applied abdominal pressure (forcefully exhaling against a closed airway)
29
The SAN is supplied by the ______ in 60% of individuals and by the _________ in the remainder.
right coronary artery, left circumflex artery
30
The AVN and proximal Bundle of His is supplied by the ____ in 90% ( right dom system) of individuals whereas the remaining 10% vines from the ____ (left dom system).
RCA, LCA
31
Inferior MI due to RCA occlusion compromises supply to AV nodal artery affecting ______, ____, and ______ which can lead to ____ and ____.
SAN, AVN, and proximal His bundle, bradycardia, high-grade AV block
32
What is an action potential?
a rapid sequence of changes in the voltage across a membrane
33
After a cardiac cell has depolarized, there is a period of time in which it ______ to any other stimuli.
won't respond
34
What is the absolute refractory period?
phase 0-3 where absolutely no other stimulus will excite the cell
35
What is the relative refractory period?
Phase 3 where a strong enough stimulus could potentially excite the cell and produce another action potential. The T wave corresponds with relative refractory period.
36
What are causes of arrhythmia?
abnormal impulse formation (enhanced automaticity- or triggered activity) and abnormal impulse transmission (re-entry phenomena or conduction disturbance)
37
What is enhanced automaticity?
inc firing of cells with pacemaker ability, abnormal firing of cells without automaticity (ex: sinus tachycardia, ischemic ventricular tachycardia)
38
What is triggered activity?
depolarization of a cell triggered by a preceding action potential, defined as early (phase 2 or 3) or late (phase 4) afterdepolarizations (early afterdepolarization- PVCs, delayed- digoxin related)
39
What is Re-Entry (Circus Movement)?
a depolarizing impulse encounters a blocked area that can only be passed on one side, impulse gets around the block on one side, circulates around it and travels back to repetitively excite a region of the heart
40
The Re-entry/Circus Movement may arise because of a ...
fixed anatomic structure (Wolff-Parkinson-White syndrome) but more commonly due to abnormal physiologic states (ischemic VT).
41
What are the sinus dysrhythmias?
sinus bradycardia, sinus tachycardia, sinus arrhythmia, sinus node dysfunction, sinus arrest, sinus exit block
42
Tell me about sinus bradycardia.
Rate: less than 60 bpm Rhythm: regular Conduction: 1:1 normal sinus P waves and PR intervals
43
What causes sinus bradycardia?
Physiologic: inc vagal tone Pharm: CCB, BB, digitalis Patho: inferior infarct, inc ICP, carotid hypersensitivity, SSS, hypothyroidism
44
Tell me about sinus tachycardia.
Rate: greater than 100 bpm Rhythm: regular Conduction: 1:1 normal sinus P waves and PR intervals
45
What causes sinus tachycardia?
Physiologic: pain, exertion Pharm: sympathomimetics, caffeine, bronchodilators Patho: fever, hypoxia, anemia, hypovolemia, PE, hyperthyroidism
46
Tell me about sinus arrhythmia.
Rate: variable Rhythm: irregular Conduction: 1:1 results from changes in autonomic tone during respiratory cycle inspiration- lowers vagal tone, inc sinus rate expiration- raises vagal tone to previous state, sinus rate decline rhythm becomes completely regular if person holds their breath
47
What causes sinus arrhythmia?
Physiologic: respiration in young healthy individuals Pharm: Morphine, digitalis (drugs that inc vagal tone) Patho: loosely associated with myocardial ischemia, obesity, DM, hypertension, herald sign of sinus node dysfunction
48
Tell me about sick sinus ("tachy-brady") syndrome.
Rate: variable Rhythm: irregular Conduction: 1:1 or 0:1 (sinus arrest w ventricular escape) Associated with sinus bradycardia, chronotropic incompetence, sinus arrest/pause, sinoatrial block
49
What causes sinus node dysfunction?
sinus bradycardia- purest form of SND, diminished automaticity chronotropic incompetence- inability of SAN to adequately inc its automaticity during physical activity sinus arrest/pause- intermittent failures to discharge impulses sinoatrial block- delayed or blocked impulse conduction between the sinoatrial node and the atrium sinus arrhythmia *in elderly*
50
Sick sinus syndrome includes sinus node dysfunction and these symptoms:
fatigue, dizziness, dyspnea, presyncope/syncope, diminished exercise tolerance
51
What causes sick sinus syndrome?
Physiologic: N/A Pharm: BB, CCB, digitalis Patho: idiopathic degenerative fibrosis (commonest), ischemia, cardiomyopathies, congenital abnormalities, hypothyroidism, electrolyte abnormalities (hyperkalemia)
52
What are the atrial dysrhythmias?
premature atrial contractions, atrial flutter, atrial fibrillation
53
Tell me about premature atrial contraction.
Rate: variable, depending on underlying rhythm Rhythm: irregular Conduction: 1:1 (or 0:1 if premature beat not conducted) occurs earlier than the next expected sinus beat, may be single or repetitive events, unifocal or multifocal (rare) in morphology PRI is normal or prolonged b/c AV junction is often partially refractory when the premature impulse enters
54
What causes premature atrial contraction (PAC)?
Physiologic: stress, fatigue Pharm: digitalis toxicity, alcohol Patho: CAD, valvular heart disease, electrolyte abnormality, hypoxia
54
Normally conducted PAC
uninhibited conduction through AVN, looks similar to other QRS complexes in the EKG
54
Non-conducted "blocked" PAC
not conducted b/c AVN is refractory
54
Conducted with aberrancy PAC
premature beat conducted past the AVN but one or more of conducting fascicles or bundle branches are refractory, resulting QRS is usually wide, sometimes called Ashman beat or Ashman phenomenon
55
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