EKG Lab

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EKG Lab

• NURS 228
• Janie Best, MSN, RN, APRN, BC

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Cardiac Conduction
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ECG Paper

• ECG paper is graph paper made up of small and
  larger, heavy-lined squares
• Smallest squares are 1 mm wide and 1 mm high
• 5 small squares between the heavier black lines
• 25 small squares within each large square

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ECG Complex
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P wave PR Interval

• Normal P wave small, round, upright
• PR Interval
• Begins with the onset of the P wave and ends with
  the onset of the QRS complex
• Normally measures 0.12 to 0.20 seconds

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QRS Complex

• A QRS complex normally follows each P wave
• Consists of Q wave, R wave, and S wave
• Represents the spread of electrical impulse
  through the ventricles (ventricular
  depolarization)
• Normal - 0.04 0.10 seconds

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ST segment T wave

• Begins with the end of the QRS complex and ends
  with the onset of the T wave and is on the same
  line as the PR interval
• ST segment depression of more than 1 mm is
  suggestive of myocardial ischemia
• ST segment elevation of more than 1 mm is
  suggestive of myocardial injury or Pericarditis

• T wave - Represents ventricular repolarization
• The beginning of the T wave is identified as the
  point where the slope of the ST segment appears
  to become abruptly or gradually steeper
• The T wave ends when it returns to the baseline

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ECG and the Cardiac Cycle
Isometric line
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Steps of Rhythm Analysis

• What is the rate?
• Ventricular
• Atrial
• Is the rhythm regular or irregular?
• Is there 1 P wave before each QRS?
• Is the PR interval WNL (0.12-0.20)?
• Is the QRS narrow or wide (0.04-0.10)?
• Interpret the rhythm
• Is the rhythm clinically significant?

• Also look at
• ST segment
• T wave

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Normal Sinus Rhythm (NSR)

• Ventricular rate 60-100 Regular rhythm
• Atrial Same as ventricular
• P consistent shape always positive
• P-R interval 0.12-0.20
• P wave for every QRS
• QRS complex 0.04-0.10

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Dysrhythmias

• Manifestation of abnormal electrical activity
• Some are serious, others are not
• Classified by site of origin
• Sinoatrial (SA) node
• Atrial tissue
• Atrioventricular (AV) node
• Junctional
• Ventricular tissue

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Tachydysrhythmias

• Coronary artery blood flow occurs during diastole
  (aortic valve closed)
• Shorter diastolic time ? coronary artery
  perfusion time
• ? workload of heart, ? myocardial O2 demand
• CAD (? blood flow)
• Rate gt 100 bpm (beats per minute)

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Sinus Tachycardia

• Etiology
• ? CNS response Anxiety Pain Fever Anemia
  Meds Compensatory hypovolemia
• Is client symptomatic?
• Interventions
• Identify cause, Select best Treatment
• Goal ? HR to normal levels
• ASA, ß-blockers, ACE Inhibitors
• Meds of concern

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Sinus Tachycardia

• Ventricular rate gt 100 (up to 180 bpm)
  Regular rhythm
• Atrial Same as ventricular
• P consistent shape
• P-R interval Normal
• P wave for every QRS
• QRS complex Normal

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Paroxysmal Supraventricular Tachycardia (PSVT)

• Paroxysmal supraventricular tachycardia is a
  term used to describe SVT that starts and ends
  suddenly

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Bradydysrhythmias

• HR lt 60 bpm
• ? myocardial O2 demand
• Prolongs diastole
• Coronary perfusion pressure may ? if HR too slow
  to provide adequate CO BP
• If BP adequate, will tolerate slow rate
• If BP not adequate, symptomatic (may lead to
  myocardial ischemia, MI, HF)

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Sinus Bradycardia

• Etiology
• PNS dominant Excessive vagal (Valsalva)
  stimulation to the heart (? SA node discharge ?
  HR, ? conduction)
• Is client symptomatic?
• Interventions
• Atropine Tx of choice
• Volume replacement
• Pacemaker placement

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Sinus Bradycardia

• Ventricular rate lt 60 regular rhythm
• Atrial same as ventricular
• P consistent shape
• P-R interval Normal
• P wave for every QRS
• QRS complex Normal

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Atrial Flutter

• Etiology
• AV node selectively blocks impulses that reach
  ventricles (protective mechanism)
• Rheumatic Heart disease, CHF, AV valve disease,
  post cardiac surgery
• Clinical manifestations dependent upon
  ventricular response
• Interventions
• O2
• Meds amiodarone, Cardizem, verapamil (older and
  seldom used drug choice)

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Atrial Flutter

• Ventricular rate Variable, Regular rhythm
• Atrial 250-300/minute, Regular rhythm
• P shape sawtooth formation
• P-R interval Absent
• No P wave
• QRS complex
• Normal

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Atrial Fibrillation

• Etiology
• Most common dysrhythmia in US
• Aging, MI, HF, MS, Cardiomyopathy
• Multiple, rapid impulses many atrial foci Atrial
  depolarization disorganized and chaotic
• No atrial contraction, Irregular ventricular
  response
• Can lead to formation of multiple thrombi in
  cardiac chambers

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Atrial Fibrillation

• Symptoms
• SOB
• Fatigue
• Weakness,
• Distended neck veins
• Anxiety
• Syncope
• Palpitations
• Chest discomfort
• Irregular pulse

• Commonly seen after cardiac surgery (transient)
• Can be intermittent or chronic

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Atrial Fibrillation

• Interventions
• If initial Atrial fib lt 48 hrs the treatment is
  aimed to ? ventricular response convert to NSR
• ß-blockers, Ca channel blockers
• Antiarrhythmics (conversion to NSR)
• Cardioversion synchronized countershock
• If in atrial fib gt 48 hrs
• Anticoagulant therapy

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Atrial Fibrillation

• Ventricular rate lt 100 (controlled), irregular
• Atrial Unable to determine (lt 350)
• No P waves (fibrillatory waves)
• P-R interval Absent
• QRS complex Normal

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Atrial Fibrillation
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Premature Ventricular Contractions (PVC)

• Etiology
• Early ventricular complexes, followed by pause
• Ventricular contraction originating in an ectopic
  focus outside ventricles
• Aging, MI, HF, Caffeine, ? K
• Assessment
• Asymptomatic or Symptomatic
• Palpitations, Chest Pain (lack of perfusion)
• Can be warning (onset of VT, VF, R on T
  phenomenon) AMI

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Premature Ventricular Contractions

• Interventions
• If symptomatic
• Identify eliminate cause
• O2, Antiarrhythmics (lidocaine)
• MONA
• Morphine
• Oxygen
• Nitroglycerine
• ASA

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Premature Ventricular Contractions

• Interrupts basic rhythm
• Occurs early in the R-R cycle
• No P wave w/ PVC
• QRS wide and unusual

PVC
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PVCs
Unifocal PVCs
Multi-focal PVCs
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Refractory The extent to which a cell is able
to respond to a stimulus

• Absolute refractory period
• Onset of QRS complex to approximately peak of T
  wave
• Cardiac cells cannot be stimulated to conduct an
  electrical impulse, no matter how strong the
  stimulus
• Relative refractory period
• Corresponds with the downslope of the T wave
• Cardiac cells can be stimulated to depolarize if
  the stimulus is strong enough

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R on T phenomenon

• Appearance of PVC on T wave of preceding normal
  beat
• Can lead to Ventricular Fibrillation
• May see with MI

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Ventricular Tachycardia (V Tach)

• Etiology
• Repetitive firing of an irritated ventricular
  ectopic focus
• Intermittent, nonsustained VTach (NSVT)
• Sustained gt 15-30 sec
• SA node discharges independently (atria
  depolarize, not the ventricles AV dissociation)
• P waves seldom seen in sustained V Tach
• AMI, CAD, K imbalance, gt QT interval, Cardiac
  surgery, Digoxin toxicity

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V Tach

• Assessment
• Depends on ventricular rate
• Slower rates better tolerated
• Interventions Treat cause
• Sustained
• O2, ECG, Antiarrhythmics (amiodarone)
• Elective cardioversion
• Unstable
• Emergency cardioversion, O2, antiarrhythmics
• Pulseless
• Defibrillation

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Ventricular Tachycardia (V Tach)

• Unable to determine rhythm
• Regular ventricular rate (100-250)
• No P waves present
• QRS complex gt 0.10 sec

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V Tach
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V Fib

• Chaotic electrical activity
• No discernable P-QRS-T complexes
• Cardiac arrest
• Etiology
• Ventricles quiver, consume lots of O2, No
  cardiac output, no perfusion
• AMI, ? K, ? Mg
• Rapidly fatal (3-5 min)

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V Fib

• Assessment
• LOC, Absence of Pulse
• Apnea
• Seizures
• Development of respiratory metabolic acidosis
• Treatment
• CPR (ACLS)
• Defibrillation - pulseless
• Drug of choice Amiodarone, Lidocaine, Magnesium
  Sulfate (for hypomagnesemia or torsades de
  pointes)

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Ventricular Fibrillation (V Fib)
Coarse
Fine
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Asystole

• Ventricular standstill
• Complete absence of any ventricular rhythm
• Etiology
• No electrical impulses, No depolarization
• No cardiac output, VS
• No impulses reach ventricles if SA fires
• Cardiac arrest, Unresponsive
• Intervention ACLS
• Make sure not in Fine V Fib

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Heart Blocks

• Occur when there is a delay in the conduction of
  the impulse through the AV node
• PR is gt 0.20 seconds
• SA node function is normal

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Heart Blocks Overview

• 1st degree
• PR interval gt 0.20 seconds
• All impulses reach the ventricles
• 2nd degree (2 types)
• Mobitz I each impulses takes longer to conduct
  until 1 is blocked and a QRS complex is dropped
  and a pause occurs then cycle repeats
• Mobitz II Impulses are blocked at a regular
  interval causing dropped QRS complexes
• 3rd degree
• None of the atrial impulses reach the ventricles
• Activity of the atria and ventricles is
  divorced
• Results in inadequate cardiac output
• Requires pacemaker

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Pacemakers
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Ventricular pacemaker
Atrial Ventricular pacemaker
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Pacemakers
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Analysis

• Expected Outcomes
• Return to baseline HR
• No adventitious breath sounds
• Cognitive status intact
• Baseline skin color/temp
• VS, BP WDL

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Analysis

• Altered Tissue Perfusion r/t ? cardiac output
• Decreased cardiac output r/t mechanical and/or
  electrical dysfunctions