Docstoc

EKG_Class

Document Sample
EKG_Class Powered By Docstoc
					   EKG
                     What you as the
                     medic needs to
                     know

SPC Farrar, Shawna
  Task, Conditions, Standards
• Task: To instruct 68W in understanding
  and recognizing specific cardiac rhythms

• Conditions: Classroom setting full of
  highly motivated Lifeline Medics

• Standard: Ensure all personnel in
  attendance understand the basic rhythms
  and can identify basic components on an
  EKG
            EKG vs ECG
• Electrocardiogram (EKG) measures the
  electrical activity of the heart
• Echocardiogram (ECG) uses sounds
  waves to generate images of the heart,
  similar to an ultra sound of the heart
EKG
Electrical Conduction System
EKG is recorded at a speed of 25 mm/sec, and the voltages are
calibrated so that 1 mV = 10 mm in the vertical direction. Therefore,
each small 1-mm square represents 0.04 sec (40 ms) in time and 0.1
mV in voltage.

P Wave represents the wave of depolarization that spreads from the
SA node throughout the atria. Shape of the wave can change if the
“pacemaker” of the heart moves from the SA node.

QRS complex represents ventricular depolarization.

Isoelectric Period (ST segment) following the QRS is the time at
which the entire ventricle is depolarized and roughly corresponds to
the plateau phase of the ventricular action potential.

T wave represents ventricular repolarization and is longer in duration
than depolarization (i.e., conduction of the repolarization wave is
slower than the wave of depolarization).
Sometimes a small positive U wave may be seen following the T
wave It represents the last remnants of ventricular repolarization.

Q-T interval represents the time for both ventricular depolarization
and repolarization to occur.

No distinctly visible wave representing atrial repolarization because
it occurs during ventricular depolarization. Because the wave of
atrial repolarization is relatively small in amplitude it is masked by
the much larger ventricular-generated QRS complex.

You can calculate the heart rate by counting the small squares and
dividing the number by 1500. (i.e., 21 small squares. 21/1500 =
.014. Heart beats ONCE every 1.4 seconds, or roughly 43 bpm)
                    Normal Values
P wave rate 60-100 bpm with <10%
variation
     Height of wave < 2.5 mm in lead II
     Width <.11 s in lead II
PR Interval 0.12  0.20 s (3-5 small
squares)
QRS Complex < 0.12 s duration (3 small
squares)
QT interval (QTc) = dividing QT interval
by square root of preceeding R-R interval.
  Normal = .42 s (380-420 ms)
ST segment = no elevation/depression
T wave
U wave
      Artifacts in the EKG Reading



Artifact occurs when something causes a disruption in
monitoring. Some common causes are:
•AC interference -causes 60 cycle artifact
•Muscle tremors
•Respiratory artifact-wandering baseline
•Loose electrode
•Broken lead wire
•Faulty Wiring in the EPTF
                 The Heart
• Every cell in the heart can act as a
  pacemaker.
• The SA node has an intrinsic heart beat
  generation of 60-80 bpm. “Pacemaker” of
  the heart.
• The AV node has a rate of 40-60 bpm.
  Responsible for “holding” the impulse until
  the ventricles are ready to receive them.
• The ventricles generate rates of 20-40
  bpm.
           The Heart (con’t)
• The ventricles may kick in if the cells of the
  upper chambers fail or if the electrical
  signals to the ventricle are blocked.
• A normal heart pushes at least 50-60% of
  the blood in the ventricle out to the body
  when it beats
• Heart has 2 types of cells, electrical
  (conductive) and mechanical (contracting)
• EKG evaluates the electrical cells.
  Pulse/BP evaluates the mechanical cells.
• Premature Atrial Contractions (PACs) –
  when the atrium beats early

• Premature Ventricular Contraction (PVCs)
  – when the ventricle beats early

• Everyone has the occasional palpitation,
  PAC, PVC. It becomes an issue when it
  begins to occur regularly
Rate         normal or accelerated
             usually have a different morphology than sinus
P wave       P waves because they originate from an ectopic
             pacemaker
QRS          normal
             normal, however the ectopic beats may have a
Conduction
             different P-R interval.
             PAC's occur early in the cycle and they usually
Rhythm
             do not have a complete compensatory pause.
Rate            variable
P wave          usually obscured by the QRS, PST or T wave of the PVC

                wide > 0.12 seconds; morphology is bizarre with the ST segment and the T wave
QRS
                opposite in polarity. May be multifocal and exhibit different morphologies.

                the impulse originates below the branching portion of the Bundle of His; full
Conduction
                compensatory pause is characteristic.
                irregular. PVC's may occur in singles, couplets or triplets; or in bigeminy,
Rhythm
                trigeminy or quadrigeminy.


         PVCs can occur in healthy hearts. For example, an increase in
         circulating catecholamines can cause PVCs. They also occur in
            diseased hearts and from drug (such as digitalis) toxicities
      Abnormal Rhythms


  Rhythm disturbances are classified
 according to whether they arise from the
 atrium or the ventricle, whether they are
fast or slow, and whether they are regular
                or irregular
            Tachycardia
Rapid heart rates can originate from either
 the atrium or the ventricle. Rhythms from
the ventricle are more often considered life
                 threatening.
               Bradycardia
• Usually due to heart blockage and the
  aging of the electrical wiring of the heart.
  Can be treated utilizing a pacemaker
         Sinus Tachycardia
• (Sinus = from SA node, Tachy=rapid,
  Cardia=heart) Rapid Regular Heartbeat
• Occurs when the body asks the heart to
  pump more blood, or when the electrical
  system is stimulated by chemicals
• Occurs most frequently during times of
  physiologic stress, exercise, dehydration,
  ingestion of medications/drugs, hormones
  within the body
Rate         101-160/min
P wave       sinus
QRS          normal
Conduction   normal
Rhythm       regular or slightly irregular



       The clinical significance of this dysrhythmia depends on
         the underlying cause. It may be normal. Underlying
        causes include: increased circulating catecholamines,
       CHF, hypoxia, physical exercise, increased temperature,
                       stress, response to pain .
         Sinus Bradycardia
• (sinus=sa node, brady=slow, cardia=heart)
• Heart beat generated by SA node at rate
  slower than 60 bpm.
• May be normal for people who are
  active/athletic, or pt’s taking medications
  designed to slow heart rate (beta blockers
  or Ca channel blockers)
Rate         40-59 bpm
P wave       sinus
QRS          normal (.06-.12)
             P-R normal or slightly prolonged at slower
Conduction
             rates

Rhythm       regular or slightly irregular




   This rhythm is often seen as a normal
   variation in athletes, during sleep, or in
       response to a vagal maneuver.
        Vasovagal Syncope
• Episode of profound sinus bradycardia
  associated with noxious stimulus where
  the vagal system of the body kicks in.
• Sympathetic system of the body is
  mediated by adrenaline.
• Parasympathetic system is mediated by
  vagus nerve and chemical acetylcholine;
  promotes opposite body reaction than
  adrenaline
      Ventricular Tachycardia
• Rapid heart rhythm that originates from
  the lower chambers (ventricles) of the
  heart
• Prevents heart from filling adequately with
  blood; less blood is able to pump through
  the body
             usually between 100 to 220/bpm, but can be as rapid as
Rate
             250/bpm

P wave       obscured if present and are unrelated to the QRS complexes.
QRS          wide and bizarre morphology
Conduction   as with PVCs
             three or more ventricular beats in a row; may be regular or
Rhythm
             irregular.


Ventricular tachycardia almost always occurs in diseased hearts.
Some common causes are CAD, acute MI, digitalis toxicity, CHF,
                      ventricular aneurysms.
      Patients are often symptomatic with this dysrhythmia.
 Ventricular tachycardia can quickly deteriorate into ventricular
                             fibrillation
  Ventricular Fibrillation (V Fib)
• Heart has ceased to beat, ventricles do
  not have a coordinated electrical pattern.
  Ventricles do not beat, but “jiggle”
Rate         unattainable
P wave       may be present, but obscured by ventricular waves
QRS          not apparent
Conduction   chaotic electrical activity
Rhythm       chaotic electrical activity




   This dysrhythmia results in the absence of cardiac output.
  Almost always occurs with serious heart disease, especially
                           acute MI.
      Atrial Fibrillation (A Fib)
• Atrium has lost ability to beat in a
  coordinated fashion.
• SA node fails to generate single electrical
  signal; numerous areas of atrium become
  irritated and produce electrical impulses.
• Atrium “jiggles” rather than beat; causes
  ventricles to fire irregularly, often quickly
Rate         atrial rate usually between 400-650/bpm.

P wave       not present; wavy baseline is seen instead.

QRS          normal

             variable AV conduction; if untreated the ventricular response
Conduction
             is usually rapid.

             irregularly irregular. (This is the hallmark of this
Rhythm
             dysrhythmia).


  Atrial fibrillation may occur suddenly, but often becomes chronic.
  It is usually associated with COPD, CHF or other heart disease
              Heart Blocks
• When involving ventricles, often
  asymptomatic and of little consequence
• When involving atrium, classified as first,
  second, and third degree
• Heart beats slowly, causing decreased
  cardiac output
Rate                     normal or bradycardia
P wave                   those present are normal
QRS                      normal
Conduction               normal
Rhythm                   basic rhythm is regular*.

  In a type I SA block, the P-P interval shortens until one P
                       wave is dropped.

 In a type II SA block, the P-P intervals are an exact multiple
    of the sinus cycle, and are regular before and after the
                        dropped P wave.
       1st Degree Heart Block
• Common and of little significance
• Slight delay in getting the electrical signal
  from the SA node to the AV node
• Heart functions normally
Rate         variable
P wave       normal
QRS          normal
             impulse originates in the SA node but has prolonged
Conduction   conduction in the AV junction; P-R interval is > 0.20
             seconds.
Rhythm       regular


This is the most common conduction disturbance. It occurs
   in both healthy and diseased hearts. Causes include
inferior MI, digitalis toxicity, hyperkalemia, increased vagal
          tone, acute rheumatic fever, myocarditis.
      2nd Degree Heart Block
• Two Types: Mobitz I & Mobitz II
• Mobitz II can be precursor to life
  threatening rhythm problem
Rate            variable
P wave          normal morphology with constant P-P interval
QRS             normal

                the P-R interval is progressively longer until one P wave is
Conduction
                blocked; the cycle begins again following the blocked P wave.

Rhythm          irregular



Second degree AV block type I occurs in the AV node above the
Bundle of His. It is often transient and may be due to acute inferior
MI or digitalis toxicity. Often asymptomatic.
Rate         variable
P wave       normal with constant P-P intervals

             usually widened because this is usually associated with a bundle
QRS
             branch block.

             P-R interval may be normal or prolonged, but it is constant until
Conduction
             one P wave is not conducted to the ventricles.

Rhythm       usually regular when AV conduction ratios are constant


This block usually occurs below the Bundle of His and may
progress into a higher degree block. It can occur after an acute
anterior MI due to damage in the bifurcation or the bundle
branches. More serious than the type I block.
      3rd Degree Heart Block
• Describes complete loss of connection
  between electrical activity of the atrium
  and the ventricle
• 2nd & 3rd Degree heart blocks are
  diagnosed by analyzing heart rhythm
  strips and EKGs
               atrial rate is usually normal; ventricular rate is usually less than 70/bpm. The
Rate
               atrial rate is always faster than the ventricular rate.

P wave         normal with constant P-P intervals, but not "married" to the QRS complexes.
               may be normal or widened depending on where the escape pacemaker is
QRS
               located in the conduction system
               atrial and ventricular activities are unrelated due to the complete blocking of
Conduction
               the atrial impulses to the ventricles.
Rhythm         irregular


   Complete block of the atrial impulses occurs at the A-V junction,
  common bundle or bilateral bundle branches. Another pacemaker
   distal to the block takes over in order to activate the ventricles or
  ventricular stand still will occur. May be caused by digitalis toxicity,
    acute infection, MI, and degeneration of the conductive tissue
QUESTIONS

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:29
posted:9/25/2012
language:English
pages:42