MS1 Chapter 25

• Electrical activity flows through the heart in the following way:

  • SA node: primary pacemaker of the heart, beats at 60 to 100 per minute
  • AV node: takes over if the SA node slows or fails, beats at 40 to 60 per minute
  • Bundle of His, Right & Left Bundle Branches, Purkinje fibers
• Six steps used for arrhythmia interpretation:

  1. Regularity of rhythm

  2. Heart rate calculation

  3. Examination of P waves

  4. PR Interval measurement

  5. QRS Interval measurement

  6. QT Interval measurement
• Current medical treatments for cardiac arrhythmias include:

  • Medications
  • Cardioversion
  • Ablation therapy
  • Implantable devices like pacemakers and implantable cardioverter defibrillators
• Cardiac pacemakers and implantable cardioverter defibrillators (ICDs) are used for:

  • Regulating heart rhythms
  • Delivering electrical shocks to restore normal heart rhythm
• Nursing care for patients with an arrhythmia involves:

  • Monitoring heart rhythm
  • Administering medications as prescribed
  • Educating patients on lifestyle changes
• Nursing care for patients with an implanted device includes:

  • Monitoring device function
  • Educating patients on device care and maintenance
  • Recognizing and managing device-related complications
• Atrial Flutter:

  • Atria contract or flutter at a rate of 250 to 350 bpm
  • Some impulses get through the AV node and reach ventricles
  • Results in normal QRS complexes
  • Signs and symptoms: Ventricular rate normal, rapid ventricular rate, palpitations, angina, dyspnea
  • Therapeutic interventions to slow heart rate: Cardioversion for unstable patient with a rapid ventricular rate, rapid atrial pacing, calcium channel blocker to control ventricular rate, catheter ablation
• • Therapeutic interventions: Synchronized cardioversion if unstable, medications (beta blocker, calcium channel blocker, digoxin), anticoagulation to reduce thrombi and stroke risk, cardioversion to convert rhythm to NSR (after anticoagulation), catheter ablation, cryothermy or radiofrequency energy, surgical maze procedure
• Atrial Fibrillation:

  • NO P WAVES!
  • Rhythm: Irregularly irregular
  • Heart rate: Atrial rate not measurable; ventricular rate: < 100 = controlled response, > 100 = rapid ventricular response
  • P waves: No identifiable P waves
  • PR interval: None measurable
  • QRS interval: 0.06-0.10 seconds
  • Atrial rate extremely rapid and chaotic; 350 to 600 bpm can occur
  • AV node blocks most of the impulses
  • Ventricular rate is much lower than the atrial rate
  • Signs and symptoms: Palpitations, racing heart, skipping a heartbeat, dyspnea, dizziness, chest discomfort
• Third-Degree Atrioventricular Block:

  • Rhythm: Regular, atria/ventricles independent
  • Heart rate: Atrial 60 to 100 beats per minute, 20 to 40 beats per minute (ventricular focus), 40 to 60 beats per minute (junctional focus)
  • P waves: Normal appearance; independent of QRS complex; more P waves than QRS complexes
  • PR interval: None
  • QRS interval: > 0.10 seconds (ventricular focus), 0.06-0.10 seconds (junctional focus)
  • Electrical impulses not conducted from SA node to stimulate ventricles to contract
  • Escape impulses (junctional/ventricular) required for survival
• • No relationship between atria and ventricles
  • Causes: Cardiac ischemia or infarction, hyperkalemia, infection, antiarrhythmic medications, or digoxin toxicity
  • Symptoms: Confusion, shortness of breath, severe chest pain, hypotension, syncope, dizziness, fatigue
  • Therapeutic interventions: Medical emergency, atropine considered, temporary pacemaker, permanent pacemaker possibly for lifetime
• Defibrillation:

  • Electrical shock (high energy 120-200 or 360 joules) to reset lethal ventricular arrhythmias
  • Pulseless ventricular tachycardia, ventricular fibrillation
  • Saline pads or conductive jelly with pads used
  • Paddles pressed firmly against chest
  • Must announce “clear” for safety
  • Only 2 shockable rhythms for defibrillation
• Ventricular Arrhythmias:

  • Premature ventricular contractions (PVC's)
  • Ventricular tachycardia
  • Ventricular fibrillation
• Premature Ventricular Contractions (PVC's):

  • Unifocal PVC's arise from one foci (area) and look the same; same irritable ventricular area
  • Multifocal PVC's arise from different foci and may look different; several irritable areas in the ventricle
  • PVC's occur when the ventricle beats early
  • Rhythm: PVC's interrupt rhythm
  • Heart rate: Per underlying rhythm
  • P waves: Absent in PVC's
  • PR interval: None for PVC's
  • QRS interval: PVC's > 0.10 seconds
  • Repetitive cycles or patterns of PVC's: Bigeminy, trigeminy, quadrigeminy, couplet, run of PVC's
• • Signs and symptoms: Palpitations, fatigue, dizziness, severe arrhythmias
  • Therapeutic interventions: None, antiarrhythmics if dangerous, beta blocker, calcium channel blocker
• Ventricular Tachycardia:

  • 3 or more PVC's in a row
  • Rhythm: Usually regular
  • Heart rate: 150 to 250 ventricular beats per minute
  • Slow ventricular tachycardia (VT) < 150 beats per minute
  • P waves: Absent
  • PR interval: None
  • QRS interval: WIDE; > 0.10 seconds
  • Ventricles rather than the SA node become the pacemaker of the heart
  • Signs and symptoms: Sudden onset of rapid heart rate, dyspnea, palpitations, lightheadedness, angina, cardiac arrest “pulseless VT”
• • Causes: Myocardial irritability, MI, cardiomyopathy, respiratory acidosis, hypokalemia, digoxin toxicity, cardiac catheters, pacing wires
  • Therapeutic interventions: Antiarrhythmics if stable, CPR, immediate defibrillation for pulseless VT, ACLS protocol: epinephrine, amiodarone
• • Signs and symptoms: Unconscious, no heart sounds, peripheral pulses, or blood pressure, respiratory arrest, cyanosis, pupil dilation
  • Therapeutic interventions: Immediate defibrillation “shock”, CPR, endotracheal intubation and oxygen, ACLS protocols, epinephrine, amiodarone
• Ventricular Fibrillation:

  • Rhythm: Chaotic, extremely irregular
  • Heart rate: Not measurable
  • P waves: None
  • PR interval: None
  • QRS interval: None
  • Ventricular activity chaotic
  • No discernible waves
  • Ventricle quivers
  • Unable to initiate a contraction
  • Complete loss of cardiac output
  • Death occurs if not immediately corrected
  • Causes: Hyperkalemia, hypomagnesemia, electrocution, coronary artery disease, MI, placement of intracardiac catheters, cardiac pacing wires
• Asystole:

  • NO ELECTRICAL ACTIVITY; “CARDIAC ARREST”
  • Rhythm: None
  • Heart rate: None
  • P waves: None
  • PR interval: None
  • QRS interval: None
  • Causes: Hyperkalemia, VF, or a loss of a majority of functional cardiac muscle due to an MI
  • VF usually precedes asystole. VF must be reversed immediately to help prevent asystole
  • Cardiac arrest
  • Signs and symptoms: Unconscious, unresponsive, no heart sounds, peripheral pulses, or blood pressure
  • Therapeutic interventions: CPR, endotracheal intubation with oxygen, ACLS protocols, epinephrine, treat cause, no shock for asystole
• Cardiac Pacemakers:

  • Generate an electrical impulse
  • Traditional types: External and temporary, internal and permanent
  • Leads placed in atria, ventricle, or both
  • Spike (vertical line) on ECG begins paced beat
• Patient Pacemaker Education:

  • Incision care, dressing removal, keeping it clean and dry, resuming showers
  • Activity restrictions: Limit raising arm on pacemaker side, driving, returning to work
  • Symptoms or infection signs to report
  • Carry pacemaker ID card
  • Periodic pacemaker checks
• Review Question:

  • On the ECG paper, one small square is equal to 0.02 seconds of time
  • What is seen on an ECG tracing when there is no electrical activity being produced? Isoelectric line
  • What is the normal PR interval? 0.12 to 0.20 seconds
  • Which of the following arrhythmias may be defibrillated? Ventricular Fibrillation, Pulseless Ventricular Tachycardia