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Case ScenarioCase Scenario
An 87-year-old woman reports feeling weak and short of breath for 2 hours while walking short distances. She feels exhausted moving from the car to the ED stretcher. On physical exam she is pale and sweaty; HR = 35 bpm; BP = 90/60 mm Hg; RR = 18 rpm. Rhythm: see next slide.
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87-Year-Old Woman:Symptomatic Bradycardia
87-Year-Old Woman:Symptomatic Bradycardia
Identify A, B, and C Which one is most likely
to be her rhythm?A
B
C
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Rhythms to LearnRhythms to Learn
Sinus bradycardia Heart blocks
• 1st degree
• 2nd degree type I
• 2nd degree type II
• 3rd degree
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Cardiac Conduction System 1Cardiac Conduction System 1
Left bundle branch
Posterior division
Anterior division
Purkinje fibersRight bundle branch
Bundle of His
AV node
Internodal pathways
Sinus node
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Cardiac Conduction System 2Cardiac Conduction System 2
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Rates of Intrinsic Cardiac Pacemakers
Rates of Intrinsic Cardiac Pacemakers
Primary pacemaker
• Sinus node (60-100 bpm) Escape pacemakers
• AV junction (40-60 bpm)
• Ventricular (<40 bpm)
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Determining the RateDetermining the Rate
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Determining the RateDetermining the Rate
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Analyzing Rhythm StripsAnalyzing Rhythm Strips
Key questions
• Are QRS complexes present?
• Are P waves present?
• How is the P wave related to the QRS complex?
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Relationship of P Waves and QRS Complexes
Relationship of P Waves and QRS Complexes
Every P wave is followed by a QRS complex with a normal P–R interval
Every P wave is followed by a QRS complex but the P–R interval is prolonged
Some P waves are not followed by a QRS complex; more P waves than QRS complexes
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What Is This Rhythm?What Is This Rhythm?
Sinus BradycardiaSinus Bradycardia
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What Is This Rhythm? What Is This Rhythm?
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First Degree AV BlockFirst Degree AV Block
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Diagnosis?Diagnosis?
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Second Degree AV Block Type ISecond Degree AV Block Type I
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Diagnosis?Diagnosis?
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Second Degree AV Block Type IISecond Degree AV Block Type II
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What Is This Rhythm?What Is This Rhythm?
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Third Degree AV Block Type IIIThird Degree AV Block Type III
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Differentiation of Second- andThird-Degree AV Blocks
Differentiation of Second- andThird-Degree AV Blocks
More P’s than QRSs
PR fixed?
no
QRSs thatlook alikeregular?
no
yes
yes
yes
2nd-degree AV blockFixed
Mobitz II
3rd-degree AV block
2nd-degree AV blockVariableMobitz I
Wenckebach
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Bradycardia Algorithm (1 of 2) Bradycardia Algorithm (1 of 2)
Bradycardia
Heart Rate less than 60 bpm and inadequate for clinical condition
• Maintain patent airway; assist breathing as needed• Give oxygen• Monitor ECG (identify rhythm), blood pressure, oximetry• Establish IV access
Serious signs or symptoms of poor perfusion caused by the
bradycardia?(eg. acute altered mental status, ongoing chest pain, hypotension or other signs of shock)
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Bradycardia Algorithm (2 of 2)Bradycardia Algorithm (2 of 2)
Observe/Monitor
• Prepare for transvenous pacing• Treat contributing causes• Consider expert consultation
Poor Perfusion
Adequate Perfusion
• Prepare for transcutaneous pacing; use without delay for high degree block (type II second -degree block or third-degree AV block)
• Consider Atropine 0.5 mg/IV while awaiting pacer. May repeat to a total dose of 3 mg. If ineffective, begin pacing.
• Consider Epinephrine (2 to 10 µg/min) or dopamine (2 to 10 µg/kg/min infusion while awaiting pacer or if pacing ineffective.
Reminders• If pulseless arrest develops go to
Pulseless Arrest Algorithm• Search for and treat possible contributing
factors:• Hypovolemia• Hypoxia• Hydrogen ion (acidosis)• Hypo/Hyper-kalemia• Hypoglycemia• Hypothermia• Toxins• Tamponade, cardiac• Tension pneumothorax• Thrombosis (coronary or
pulmonary)• Trauma (hypovolemia, inc ICP)
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What Is This Rhythm?What Is This Rhythm?
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Treatment? Treatment?
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Treatment? Treatment?
Transcutaneous PacingTranscutaneous Pacing
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Indications for Transcutaneous Pacing
Indications for Transcutaneous Pacing
Hemodynamically unstable bradycardias In the setting of AMI: sinus node dysfunction,
type II 2nd-degree block, 3rd-degree heart block Bradycardia with symptomatic ventricular
escape beats
Transcutaneous PacingTranscutaneous Pacing
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Transcutaneous PacingTranscutaneous Pacing
The pacing rate is set at 80 beats per minute. In conscious bradycardic patients, pacing is begun
in the demand mode at rates slightly faster than the native rhythm and at minimal current output
The current is gradually increased by 5 to 10 mA at a time until cardiac capture is documented, which defines the pacing threshold. The final current output should be set at the pacing threshold or 5 to 10 mA above it.
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Transcutaneous PacingTranscutaneous Pacing
In the setting of a bradysystolic arrest or with unconscious patients, it is recommended to turn the stimulating current to maximal output (200 mA) to ensure ventricular capture
Once capture is achieved, the current may be gradually decreased until loss of capture, which defines the pacing current threshold
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Transcutaneous PacingTranscutaneous Pacing
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Transcutaneous Pacing:“Capture” vs “No Capture”
Transcutaneous Pacing:“Capture” vs “No Capture”
Pacing below threshold:no capture
Pacing above threshold:with capture
Pacing Spike
Capture:• Spike + broad QRS• QRS: opposite polarity
25 Feb 88 Lead I Size 1.0 HR=41
25 Feb 88 Lead I Size 1.0 HR=43 35 mA
25 Feb 88 Lead I Size 1.0 HR=71 60 mA
Bradycardia: No Pacing
Pacing Below Threshold (35 mA): No Capture
Pacing Above Threshold (60 mA): With Capture (Pacing-PulseMarker )
Bradycardia: no pacing
