Transcript “Airway, Airway – Who`s got the Airway?” Issues and Techniques in

February EMS Training:
AV Blocks & Pacing
Used with permission of Silver
Cross EMS System
Goals
• Review different heart blocks found when
completing an EKG
• Identify how to differentiate between
different heart blocks
• Review transcutaneous pacing equipment and
how to pace a patient
• Identify any other relevant treatments for
patients with a heart block
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Cardiac Rhythm of the Month
• AV Blocks
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Review - AV Junction
• AV Junction = AV Node and Bundle of His
• Pacemaker cells located throughout AV
Junction
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Review - Functions of AV Node
• Backup pacemaker for SA Node
• Creates delay between atrial and ventricular
depolarizations
• Physiologic block for rapid supraventricular
rhythms
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Degrees of AV Blocks
• First Degree - Delay in conduction
• Second Degree - Some impulses blocked
• Third Degree - All impulses blocked
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First Degree AV Block
• An abnormal slowing of AV Junction
conduction
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First Degree AV Block ECG Criteria
• Rate - Dependent on underlying rhythm
– Interpretation must include underlying rhythm
• Rhythm - Dependent on underlying rhythm
• P-Waves - Normal morphology with one PWave for each QRS
• PRI - > .20 seconds and constant
• QRS - Dependent on underlying rhythm
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First Degree AV Block Clinical
Significance
• Not usually detrimental and often resolves
when ischemia corrected
• Must consider entire patient
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Second Degree AV Blocks
• Type I
– Also called “Wenckebach”
– Also called Mobitz I
• Type II
– Also called Mobitz II
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Second Degree AV Block, Type I
• Intermittent block in which AV conduction
gradually slows until an impulse is blocked
• “Long, longer, longer, drop! Long, longer,
longer, drop!”
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Second Degree AV Block, Type I
ECG Criteria
 Rate - Atrial rate unaffected but ventricular rate
is less than atrial rate
 Rhythm - Atrial rhythm usually regular.
Ventricular rhythm is irregular with more PWaves than QRS Complexes.
 P-Waves - Unaffected with more P-Waves than
QRS Complexes
 PRI - Progressively increases for consecutively
conducted P-Waves until QRS Complex is
dropped
 QRS - Unaffected
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Second Degree AV Block, Type I
Etiology
• Often caused by increased parasympathetic
tone or drug effect
• Can be caused by MI
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Second Degree AV Block, Type I Clinical
Significance
• Usually transient with good prognosis
• Can reduce cardiac output due to bradycardia
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Second Degree AV Block, Type II
• Intermittent block in which not all P-Waves
are conducted to ventricles but there is no
progressive prolongation of PRI
• “Extra” p-waves.
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Second Degree AV Block, Type II
Etiology
• Usually due to MI or other organic heart
disease
• Rarely the result of increased parasympathetic
tone or drug effect
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Second Degree AV Block, Type II
Clinical Significance
• Poorer prognosis than Type I
• Usually requires pacemaker
• Frequently develops into Complete Block
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Second Degree AV Block, Type II
ECG Criteria
 Rate - Atrial rate is unaffected but ventricular
rate is less than atrial
 Rhythm - Atrial rhythm regular, Ventricular
irregular with more P-waves than QRS
Complexes
 P-Waves - Normal morphology with more PWaves than QRS Complexes
 PRI - Constant for consecutively conducted PWaves
 QRS - Usually wide but may be narrow if block
is at His level or above
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Second Degree AV Block, Type II
Example
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Third Degree AV Block
• Complete blockage of impulse conduction
through AV Junction
• Results in “AV dissociation” (very very bad
thing)
• P’s and QRS’s “march to their own drummer”
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AV Dissociation
• No relationship between P-waves and QRS
complexes
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Third Degree AV Block Etiology
• MI
• Increased parasympathetic tone
• Drug toxicity
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Third Degree AV Block ECG Criteria
•
•
•
•
Rate - Atrial > 60, Ventricular based on escape
Rhythm - Atrial and ventricular regular
P-Waves - Normal
PRI - No association between P-Waves and
QRS complexes (P’s and QRS’s are divorced
and do their own thing)
• QRS - Narrow if intranodal, Wide if infranodal
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Transcutaneous Pacing (TCP)
• Non-invasive electrical therapy for
symptomatic bradycardias/complete heart
blocks
• Fast to set up
• Reasonably reliable
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TCP Equipment
• Give the patient Versed if they are awake, per
SMO
• Set milliamps (adjustable 0-200mA typical)
– Start low if they are awake, and high if they are
out.
• Set rate to 70.
• Similar controls across brands
• Be familiar with your equipment!
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Typical TCP Controls
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Assess Electrical and Mechanical
Capture
• Electrical
– Displayed on monitor
• Mechanical
– Pulse
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