Chapter 32: Cardiac Dysrhythmias

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Chapter 32 Cardiac Dysrhythmias

• VOCN 1329 Medical Surgical I

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Overview

• Cardiac rhythm refers to the pattern (or pace) of
  the heartbeat.
• Usual cardiac rhythm is called normal sinus
  rhythm
• An arrhythmia (also called dysrhythmia) is a
  conduction disorder that results in an abnormally
  slow or rapid regular heart rate or at an
  irregular pace
• Some do not require treatment and others require
  treatment stat or death occurs

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Overview

• The most common cause of arrhythmias is ischemic
  heart disease.
• Effects of drug therapy, electrolyte
  disturbances, metabolic acidosis, and hypothermia
  can also cause arhythmias.

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Arrhythmias Originating in the SA Node Pg 494

• Sinus bradycardia
• Sinus tachycardia
• Supraventricular Tachycardia
• Atrial flutter
• Atrial fibrillation
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Sinus Bradycardia

• Originates in Sinoatrial (SA) node.Beat is
  regular but slow lt 60. Occurs in heart disorders,
  increased intracranial pressure, hypothyroidism,
  or digitalis toxicity
• Slow rate may be insufficient to maintain cardiac
  output.
• Atropine sometimes given IV
• Healthy athletes may have bradycardia normally

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Sinus Tachycardia

• Regular but fast (100-150)
• Occurs in healthy hearts as a response to
  strenuous exercise, anxiety, fear, pain, fever,
  hyperthyroidism, hemorrhage, shock or hypoxemia

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Supraventricular Tachycardia

• Arrhythmia with a dangerously high heart rate gt
  150. Diastole is shortened and the heart does not
  have enough time to fill. Cardiac output drops
  dangerously low and heart failure can occur,
  especially if heart damage already
• If CAD can develop chest pain. Angina,
  hypotension, syncope or low cardiac output are
  signs and symptoms of low output

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Normal Sinus Rhythm

• Characteristics of Normal Sinus Rhythm Box 32-1
  on pg 494.

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Characteristics of Normal Sinus Rhythm

• Heart rate between 60 and 100
• Initiated by SA node (upright P wave before QRS
  complex)
• Impulse travels to the Atrioventricular (AV) node
  in 0.12 to 0.2 seconds (the PR interval)
  Ventricles depolarize in 0.12 sec. or less
• Each impulse occurs regularly and evenly spaced

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Atrial Flutter

• Disorder in which a single atrial impulse outside
  the SA node causes the atria to contract at an
  exceedingly rapid rate (200-400 times/min) AV
  node conducts only some of impulses to ventricle
• Atrial waves in atrial flutter have a sawtooth
  pattern

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Atrial Fibrillation

• Several areas in the right atrium initiate
  impulses resulting in a disorganized, rapid
  atrial activity. The atria quiver rather than
  contract.
• Ventricles respond to atrial stimulation
  randomly, resulting in irregular ventricular
  heart rate.
• Corvert (antiarrhythmic), digitalis and
  cardioversion used to Tx

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Atrial Fibrillation

• During atrial fibrillation the atria quiver
  rapidly
• This arrhythmia can cause clots to form within
  the heart so aspirin one daily usually recommended

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Heart Block

• Originates in the AV node
• Interferes with transmission of impulses from SA
  node thru AV node to the ventricles. May be 1st
  degree, 2nd or 3rd degree block (3rd degree also
  called complete block)
• 1st and 2nd the impulse is delayed. In 3rd it
  never gets thru and the ventricles develops their
  own beat --usually below 30-40

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Premature Ventricular Contractions

• Occurs early in cardiac cycle before the SA node
  initiates an electrical impulse.
• No P waves precedes the wide, bizarre looking
  QRS
• They often cause a flip-flop sensation in the
  chest and may be described as a fluttering

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PVCs

• Occasional PVC is usually harmless. May be
  related to stress, fatigue, alcohol withdrawal,
  or tobacco use.
• Can occur in certain patterns and suggest
  Myocardial irritability and can cause lethal
  arrhythmias.
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PVCs pg. 497

• PVCs are considered precursors of a
  life-threatening arrhythmia when he has
• Six or more PVCs per minute
• Runs of bigeminy (everyother beat is PVC
• Two PVCs in a row (couplets
• Runs of PVCs (more than 2 in a row
• Multifocal PVC (originating from more than one
  location

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PVCs

• A PVC whose R wave falls on the T wave of the
  preceding complex (R on T phenomenon. Life
  threatening!!

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Ventricular Tachycardia( V-tach) pg 497

• Caused by single, irritable focus in the
  ventricle that initaites the heart beat
• Beats 150-250 times per min and cardiac output is
  decreased.
• May lose consciousness and become pulseless
• Sometimes ends abruptly without intervention but
  often requires defibrillation as can lead to V fib

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Ventricular Fibrillation

• Is the rhythm of a dying heart.
• PVCs or Ventricular tachycardia can precipitate
  it
• Ventricles do not contract effectively and there
  is no cardiac output
• CPR and defibrillation needed

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Pathophysiology of Arrhythmias pg 498

• Most common cause of arrhythmias is myocardial
  ischemia
• Conduction system is also susceptible to
  disturbances from anxiety, pain, electrolyte
  imbalances, valvular heart disease, placement of
  invasive catheters within heart, and drugs.
• All arrhythmias affect pumping action

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Signs and Symptoms

• Feels weak, tired
• If tachyarrhythmias, will feel palpitaions or
  fluttering in chest. Some say it flip-flops.
• B/P is generally low pulse is irregular or
  difficult to palpate
• Apical radial pulse may differ
• Skin may be cool and pale. May be confused or
  disoriented

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Elective Cardioversion pg 500

• Nonemergency procedure done to stop rapid, but
  not necessarily life-threatening arrhythmias.
• Machine does not fire until it senses an R wave
  so does not land on a T wave and cause V Fib.
• Electric current depolarizes the entire
  myocardium completely so normal pacemaker can
  regain control

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Elective Cardioversion

• Consent form signed
• Restrict food and fluids
• IV line inserted
• Digitalis and diuretics withheld 24 to 72 hrs
  before as may decrease ability of heart to
  restore normal conduction and increases chance of
  fatal arrhythmia
• Crash cart in room

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Cardioversion

• Give valium or Versed IV as ordered.Sedative
  usually ordered to be given 30 min to an hour
  prior to procedure
• Insert oral airway
• Assist with bowel or bladder elimination prior to
  Tx
• Monitor vitals q 15 min after procedure for 1st 1
  to 2 hours

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Defibrillation pg 500

• Only treatment for life-threatening V tach or V
  Fib. If not done he will die
• Used during cardiac arrest when no R waves
  present
• Automatic implantable cardiac defibrillator is
  used for recurrent arrhythmias. Senses the
  arrhythmia and shocks client automatically

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Defibrillation

• Instituted as soon as arrhythmia identified
• CPR done until defib can be initiated
• Remove nitroglycerine patch if present
• Protect skin with saline pads or gel the
  electrode paddles. Charge the paddles
• Stand clear warn others
• Monitor LOC, ECG pattern, BP and vitals after
  procedure

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Defibrillation

• Review labs,( arterial blood gases, serum
  electrolytes)
• Check paddle sites for redness and impaired skin
  integrity.
• Keep defibrillator on standby as may need to
  repeat
• Monitor urinary output, motor weakness,
  paralysis, memory impairment, LOC to detect
  effects of cerebral anoxia

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Pacemaker pg 501

• Keep resuscitation equipment in room because
  V-Fib can occur
• Once inserted attach lead to external pacemaker
  unit
• Check connection several times daily
• If confused or restless and movement disturbs the
  external unit, notify Dr.Use only grounded
  equipment in room..plugs must have 3 prongs

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Temporary Pacemaker

• An alarm sounds if pulse drops below a certain
  level. May be due to battery failure, internal
  dislodgment of the pacemaker lead, or a break in
  pacemaker lead.
• Keep spare battery available. Call Dr if lead
  breaks. Check for spikes. Infection, perforation
  of ventricular myocardium by tip of pacemaker
  lead, arrhythmia are complications

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Instructions for Pacemaker

• Report if the suture line becomes inflamed or
  sore
• Avoid injury to the area where inserted
• Follow Drs advice regarding lifting, sports and
  exercise
• Palpate pulse and count rate for a full minute
  daily or when ill
• Wear a Medic Alert bracelet

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Instructions and Teaching

• Be cautious in situations that can cause
  pacemaker malfunction, such as gravitational
  force during airplane departures and landings,
  bumpy auto rides, high-tension wires, shortwave
  radio transmissions, telephone transformers, and
  nuclear magnetic resonance imaging (MRI). Move to
  another location and check pulse rate if
  dizziness or palpitations

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Pacemaker teaching

• Request hand scanning during airport security
  checks because some pacemakers trigger alarm
  systems
• Check with Dr. concerning transtelephone
  pacemaker checks or when pacemaker battery
  changer will be necessary in the future (usually
  good for 10 years)
• Maintain follow-up care