Basic Dysrhythmias Part I & II Questions & Answers 2023-2024 A+
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Pacemakers of the Heart
P wave
AV node conduction
AV Valves
QRS
... [Show More] complex
Sinoatrial (SA) node
Atrioventricular (AV) node
Bundle of His
Bundle Branches
Purkinje Fibers
-SA node: p wave
-SA node to AV node: PR segment
-Impulse travels from Bundle of His to
Bundle branches and then to Purkinje
fibers: QRS complex
-Repolarization of ventricles: T wave
sinoatrial node (SA node) starts an impulse, as the wave of depolarization
spreads through the atria, is
inscribed on the ECG
Is the ONLY electrical conduction pathway between the atria and ventricles.
-Depolarization is SLOWED to allow fill
time
-It is carried by SLOW Ca++ ions = slower conduction
(Na+ produces fast depolarization)
-Prevent ventricle-to-atrium blood backflow
-ELECTRICALLY INSULATE the ventricles from the atria
After leaving the AV node, the wave of
depolarization (impulse) spread rapidly
through the Bundle of His to the Bundle branches and then to Purkinje fibers;
which cause ventricular depolarization,
contraction immediately follows depolarization
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Ventricular conduction system
P-R interval
T-Wave
Sympathetic Nervous System: Cardiac
Excitability Effect
Parasympathetic Nervous System: Cardiac Inhibitory Effect
-Bundle of HIS (penetrates the AV
valves)
-Then splits into Left & Right bundle
branches
-BOTH THE BUNDLE OF HIS & BUNDLE BRANCHES ARE BUNDLES of
rapidly conducting Purkinje fibers
-Purkinje fibers use FAST MOVING Na+
ions for conduction of depolarization
-Period where there is a brief delay impulse in the AV node
SA node to AV node
Repolarization of ventricles (terminates
contraction)
activates cardiac beta-1 adrenergic receptors
-Increases rate of SA node pacing
-Increases rate of conduction
-Increases force of contraction
-Increases irritability of foci
Activates cholinergic receptors
-Decreases rate of SA node pacing
-Decreases rate of conduction
-Decreases force of contraction
-Decreases irritability of atrial and junctional foci
-Impulses originate from S-A node at
normal rate; all complexes are normal
and evenly spaced
(1) Rate: 60 to 100 beats/min
(2) Rhythm: regular (evenly space) +/-
10%
(3) P wave: must be present, and only
one must precede every QRS complex
(4) P-R interval: presents delay in AV
node; should be 0.12 to .20 seconds
(5) QRS complex: size and shape do not
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Normal sinus rhythm (NRS)
matter, but ALL QRS pattern must look
alike; duration of 0.06 to 0.10 (half of PR
interval)
Any deviation from above is sinus tachycardia, sinus bradycardia or an arrhythmia
But is still originating from the SA node
if the above criteria is met with rate variance.
Sinus Arrhythmia
Types of sinus arrhythmias
Sinus tachycardia (ST)
Still originates from SA node and can
arise from:
(1) SINUS NODE
(2) ATRIAL CELLS
(3) AV JUNCTION
(4) VENTRICULAR CELLS
(1) SINUS BRADYCARDIA
(2) SINUS TACHYCARDIA
(3) SINUS ARRYTHMIA (not being test
on)
(4) SINUS ARREST (not being tested
on): SA node fails to pace completely,
but foci near by pick up the slack and
continue on in normal fashion
(5) SINUS BLOCK (not being tested on):
a temporary pause or missed pacing cycle, then SA node picks up again
-Everything within normal limits except
heart rate
-Rate between 101-150 bpm
-Caused by: medications (i.e. atropine,
bronchodilators), fever, pain, anxiety, dehydration, Pulmonary embolus, CHF
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Hemodynamics of sinus tachycardia
Treatment for Sinus tachycardia (ST)
-Decreases ventricular filling
-Decrease SV --> compromise CO
-Increase heart work and myocardial
oxygen demand while decreasing oxygen supply by decreasing coronary
artery filing time
-Treat underlying cause (fever, pain, anxiety, etc.)
-Some medications, such as calcium
channel blockers and beta-blockers may
be used; however, this decreases cardiac output, which can deprive heart and
other organs of adequate blood
Sinus bradycardia (SB)
-Impulses originates at S-A node at a
slow rate
SA NODE FIRES TOO SLOW
-Rate below 60 bpm (trauma, brain injury...etc)
-ALL complexes are normal and evenly
spaced
-Everything within normal limits except
heart rate
-Caused by: medications (i.e. beta blockers), athlete, brain injury
Treatment of sinus bradycardia (SB)
Treat only when symptomatic: hypo-perfusion such as hypotension, dizziness,
chest pain, or change in level of consciousness; if symptomatic follow bradycardia algorithm for treatment -->Atropine 1 mg (Q 3 to 5 min. for max
3) FIRST!! If not effective --> Transcutaneous pacing --> or dopamine (5 to
20 mcg/kg/min) or epinephrine (2 to 10
mcg/kg/min)
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-Condition is seen in well-trained athletes
at rest or others individuals at sleep; can
also occur in vagal stimulation, increased
ICP, digoxin or beta-blockers therapy,
and ischemia of sinuses node caused by
acute MI.
Bradycardia Algorithm
Identify and treat underlying cause:
-Maintain patent airway, assist breathing
as necessary
-Oxygen (if hypoxemic)
-Cardia monitoring to identify rhythm,
monitor BP and oximetry
-I.V. access
-Twelve (12)-lead ECG if available, do
not delay therapy
-Consider possible hypoxic and toxicologic cause
-If the condition does NOT persists to hypotension, acute altered mental status,
signs of shock, ischemic chest discomfort, or acute heart failure monitor and
observe, if does persist to the above,
provide treatment as follows*:
Atropine (1mg Q 3 to 5 min. for max of
3 mg), if ineffective --> transcutaneous [Show Less]