Case Scenario - College Justice & Safety Technology

Case 7 Case Scenario Case Scenario
Bradycardia
An 87-year-old woman reports On physical exam she
© 2001 American Heart Association feeling weak and short of is pale and sweaty; HR = 35
breath for 2 hours while bpm; BP = 90/60 mm Hg; RR
walking short distances. She = 18 rpm. Rhythm: see next
feels exhausted moving from slide.
the car to the ED stretcher.

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87-Year-Old Woman: 87-Year-Old Woman: Learning Objectives
Symptomatic Bradycardia Symptomatic Bradycardia
1. By the end of Case 7 be able to discuss
 Identify A, B, and C She experienced no chest • Asymptomatic vs symptomatic bradycardia
pain or ischemic symptoms • Signs and symptoms of symptomatic bradycardia
 Which one is most likely A prior to the onset of her A • Intervention agents and sequences to use
to be her rhythm? weakness and shortness of • Recognition criteria for heart blocks: 1st, 2nd (types
breath. Therefore, the only I and II), and 3rd degree
B rhythm not associated with • Pathology of conduction system in heart blocks
acute pain, rhythm A, is the
more likely cause of her 6
symptomatic bradycardia.

C 5

4

Learning Objectives What is Symptomatic? What is Symptomatic?

2. By the end of Case 7 be able to discuss  Bradycardia is symptomatic when:  Symptoms
• Significance of bradycardia in AMI patients • Heart rate is “slow” (absolute or relative) • Chest pain
• Significance of RV infarction plus • Patient has symptoms • Dyspnea
bradycardia • Symptoms are caused by bradycardia • Weakness
• Atropine pharmacology: why atropine • Altered LOC
helps some heart blocks and not others aa 8
• Set up, start, troubleshoot transcutaneous aa 9
pacing

7

What is Symptomatic? 10 What is Symptomatic? What is Symptomatic?

 Signs  Key question:  If the etiology is AMI:
• Hypotension • Is the bradycardia causing the patient to be • Treat the AMI (MONA)
• Diaphoresis ill? OR
• Pulmonary congestion • Is there some illness that is causing the aa 12
• PVCs bradycardia?
• Unstable angina
aa 11
aa

What is Symptomatic? Rhythms to Learn Drugs to Learn

 Key point:  Sinus bradycardia  The actions, indications, administration, and
• Treat the patient and NOT the monitor.  Heart blocks precautions for these drugs and therapies:
• Atropine
aa 13 • 1st degree • Dopamine
• 2nd degree type I • Epinephrine
• 2nd degree type II • Transcutaneous pacing
• 3rd degree • Isoproterenol (rarely used)

14 15

Drugs to Learn Cardiac Conduction System 1 Cardiac Conduction System 2

 Remember: Sinus node Bachmann’s bundle Relationship of ECG to anatomy
• Atropine – will not work on
denervated hearts. Why? Internodal pathways Left bundle branch 18
• Epinephrine – must be used with AV node Posterior division
caution with some patients. Why? Anterior division
Bundle of His Purkinje fibers
16
Right bundle branch

17

Determining the Rate Analyzing Rhythm Strips

 Key questions
• Are QRS complexes present?
• Are P waves present?
• How is the P wave related to the
QRS complex?

19 20 21

Relationship of P Waves and What Is This Rhythm? AV Block
QRS Complexes
First-degree AV block
 Every P wave is followed by a QRS complex Delay
with a normal P–R interval
This is First Degree Block.
 Every P wave is followed by a QRS complex
but the P–R interval is prolonged 23 24

 Some P waves are not followed by a QRS
complex; more P waves than QRS complexes

22

Diagnosis? Diagnosis? AV Block

Second-degree type I AV block

This is Sinus Bradycardia. This is Second-degree type I AV block.
Note the progressive PRI.

25 26 27

Diagnosis? AV Block Differentiation of Second- and
Third-Degree AV Blocks
Second-degree type II AV block
Non-Conducting P waves More P’s than QRSs yes 2nd-degree AV block
yes yes Fixed

PR fixed? Mobitz II

This is Second-degree type II AV block. no 3rd-degree AV block
Note the non-conducting Ps. QRSs that 2nd-degree AV block
look alike
regular? Variable
Mobitz I
no Wenckebach

28 29 30

Bradycardia Algorithm (1 of 2) Bradycardia Algorithm (2 of 2) Bradycardia Algorithm (2 of 2)

Bradycardia For example: Serious signs or symptoms?  For example:
•Slow (absolute bradycardia = rate <60 bpm) Due to bradycardia? • OR you can say that each 6 gtts = 1 µg
• 1 mg ENopinephrine or Isuprel inYe1s00 ccs NS
or aa 33
•Relatively slow (rate less than expected – 10 µgs / cc or 60 gtts / minType II second-degree AV block
or
relative to underlying condition or cause) Intervention sequence
– 7.5 µgs = 45 gtts / minThird-degree AV block?
Primary ABCD Survey • Atropine 0.5 to 1.0 mg
• Assess ABCs • Transcutaneous pacing if available
• Secure airway noninvasively
• Ensure monitor/defibrillator is available • Dopamine 5 to 20 µg/kg per minute

Secondary ABCD Survey – 5 µgs = 30 gtts / min • Epinephrine 2 to 10 µg/min
• Assess secondary ABCs (invasive airway management needed?) • Isoproterenol 2 to 10 µg/min
• Oxygen–IV access–monitor–fluids
• Vital signs, pulse oximeter, monitor BP N–o2.5 µgs = 15 gtts / min Yes
• Obtain and review 12-lead ECG
• Obtain and review portable chest x-ray Observe • Prepare for transvenous pacer
• Problem-focused history • If symptoms develop, use
• Problem-focused physical examination aa
• Consider causes (differential diagnoses) transcutaneous pacemaker until
transvenous pacer placed

31 32

Bradycardia Algorithm (2 of 2) What Is This Rhythm? AV Block

 Remember that Isoproterenol must only be This is Third-degree AV block. Third-degree AV block
considered if the patient fails to respond to Supranodal – note the atrial rate is between 48 - 70 Consistent P to P interval
other therapies.
35 36
 You must exercise extreme caution when
using it. Why?

aa 34

What Is This Rhythm? Treatment? What Is This Rhythm?

37 38 39

Treatment? Indications for Indications for
Transcutaneous Pacing Transcutaneous Pacing

 Hemodynamically unstable bradycardias  In the presence of escape beats, you must
 In the setting of AMI: sinus node dysfunction, decide
• if the PVCs are effective contractions
type II 2nd-degree block, 3rd-degree heart block • Should they be treated with pacing or
 Bradycardia with symptomatic ventricular medications (rate related fix)

escape beats

40 41 aa 42

Indications for Transcutaneous Pacing Transcutaneous Pacing:
Transcutaneous Pacing “Capture” vs “No Capture”
44
 However, 3rd degree block should NEVER be 25 Feb 88 Lead I Size 1.0 HR=41
treated with lidocaine. Why?
Bradycardia: no pacing
aa 43
Pacing Spike Bradycardia: No Pacing
Pacing below threshold: 25 Feb 88 Lead I Size 1.0 HR=43 35 mA

no capture Pacing Below Threshold (35 mA): No Capture
25 Feb 88 Lead I Size 1.0 HR=71 60 mA
Capture:
• Spike + broad QRS Pacing Above Threshold (60 mA): With Capture (Pacing-PulseMarker )
• QRS: opposite polarity 45
Pacing above threshold:
with capture

Rates of Intrinsic Pulse Generators for Drug Calculation
Cardiac Pacemakers Transvenous Pacing
 Dopamine
 Primary pacemaker Characteristics • Add 200 mgs into a 250 cc bag of IV NS
• Sinus node (60-100 bpm)  Variable output in milliamps • Patient weight is 225 lbs.
 Fixed versus demand mode • The initial dose would be ____ gtts?
 Escape pacemakers  Variable rate setting
• AV junction (40-60 bpm)  Firing and sensing indicators aa 48
• Ventricular (<40 bpm)  Familiarize yourself with the equipment!

46 47

Drug Calculation Drug Calculation Dopamine - effects

 Dopamine  Dopamine  alpha  beta
• 200 mgs into a 250 cc bag of IV NS • So…… • heart:none • heart: > rate
– 200 X 1000 µg = 200,000 µg OR • Patient weight is 225 lbs. • arteries:constriction
– 800 µg per cc OR – 225 / 2.2 lbs = 100 kgs  arteries: dilation
– 13.333 µg per gtt – 100 kgs X 5 µg/min = 500 µg/min  lungs:constriction  lungs: mild dilation
• Patient weight is 225 lbs. – 500 µg / 13.333 = 37.5 gtts per minute
• The initial dose would be ____ gtts?  Cardiac dosage range is 5 µg - 10 µg/kg/min
aa 50
aa 49 aa 51

Infarct Location Arrhythmias Escape Patterns

 RV Determining the pattern 54
• Often present with increased
parasympathetic tone Regular
Premature
 Look for volume problems with associated Speeding/slowing
hypovolemia
Pause
52 Group beats

Irregularly
Irregular

53

Action Potential of Second-Degree AV
Pacemaker Cell Block Type I

55 56