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Basic ECG

Basic ECG. Objectives. Identify the functions of the electrical conduction system of the heart. Demonstrate accurate ECG rhythm interpretation. Identify key characteristics of normal and abnormal rhythms. Sinoatrial Node (SA Node). Located in RA near SVC Normal pacemaker of heart

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Basic ECG

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  1. Basic ECG

  2. Objectives • Identify the functions of the electrical conduction system of the heart. • Demonstrate accurate ECG rhythm interpretation. • Identify key characteristics of normal and abnormal rhythms.

  3. Sinoatrial Node(SA Node) • Located in RA near SVC • Normal pacemaker of heart • Initiates an impulse • Intrinsic rate of 60-100

  4. Intra-Atrial Pathways • Located in atrial tissue between SA & AV nodes • Conducts impulse from SA  atrial musculature  AV node • Anterior, middle, and posterior tracts

  5. Atrioventricular Node(AV Node) • Located near tricuspid valve • Delays impulse from atria • Allows for ventricular filling • Protective mechanism against rapid supraventricular impulses

  6. Junctional Tissue • Tissue in lower AV node • Back-up pacemaker • Intrinsic rate of 40-60

  7. Bundle of His & R & L Bundle Branches • Bundle of His connects AV node to Right & Left bundle branches • R bundle carries impulse to RV • L bundle carries impulse to LV

  8. Ventricular Tissue • Back-up pacemaker • Intrinsic rate 20-40

  9. Purkinje System • Distal to the bundle branches • Rapidly conducts impulses to ventricular subendocardial layers

  10. ECG Paper • Horizontal axis represents time • small box = 0.04 seconds • 5 small boxes = 1 large block = 0.20 seconds • 5 large boxes = 1 second • Normal strip = 30 large boxes = 6 seconds

  11. ECG Paper cont... • Vertical axis measures: • amplitude in millimeters (mm) • electrical voltage in millivolts (mV) • 1 small block = 1 mm or 0.1 mV • 1 large block = 5 mm or 0.5 mV

  12. Terminology • Depolarization • The electrical activation of a cardiac cell • Repolarization Electrical recovery of the cardiac cell

  13. The P Wave • Atrial depolarization • Characteristics: • precedes the QRS • 2-3 mm high • 0.06-0.12 seconds • round & upright

  14. QRS Complex • Ventricular depolarization • Characteristics: • follows PR interval • < 0.12 seconds

  15. T Wave • Ventricular repolarization • Characteristics: • follows S wave • round & smooth

  16. PR Interval • Atrial impulse to the AV node-bundle of His-R & L bundles • Characteristics: • beginning of P wave to beginning of QRS complex • 0.12-0.20 seconds

  17. ST Segment • Early Ventricular Repolarization • Characteristics: • from end of QRS complex to beginning of T wave

  18. QT Interval • Ventricular depolarization & repolarization • Characteristics: • beginning of QRS to end of T wave • 0.35 to 0.45 seconds

  19. Monitoring • Five leads

  20. Electrodes & Leads • Electrodes measure the direction of electrical current • The current is transformed into waveforms • The ECG records the waveform information from different views & leads

  21. Leads • Provide different views of the heart’s electrical activity • Lead • view between a + pole & a - pole • the axis refers to the direction of the current moving through the heart • direction of the waveform on the ECG

  22. Lead Selection • Based on patient history

  23. Calculation of Heart Rates • R-R….. SMALL BOXES….. DIVIDE into 1500 • 6 SECOND METHOD • RATE CHART

  24. Determine the Rate • 1,500 method • use with regular rhythms, most accurate • 1,500 small squares = 1 minute • count small squares between 2 consecutive P waves • divide into 1,500 to get atrial rate (1500/30 = 50 bpm) • count small squares between 2 consecutive R waves • divide into 1,500 to get ventricular rate

  25. Determine the Rate cont.. • 6 Second method • good method if rhythm is irregular • use a 6 second strip • count the number of P waves for the atrial rate and multiply by 10 • count the number of R waves for the ventricular rate and multiply by 10

  26. Determine the Rate cont... • Sequence method-memorization of: 300-150-100-75-60-50-43 • for atrial rate, locate a P wave on a heavy black line • assign the next heavy black line 300 & begin counting backwards until you reach the next P wave • for ventricular rate, repeat the same sequence

  27. ECG - HOW TO READ IT? CHECK THE ATRIAL and VENTRICULAR RHYTHM Is it REGULAR OR IRREGULAR? CALCULATE THE ATRIAL AND VENTRICULAR RATE Same or different? LOOK FOR P, Q, R, S, AND T Is there a P wave for every QRS? Is there a QRS for every P? PR Interval? QRS width? FIND THE ORIGIN Sinus, Atrial, Junctional, or Ventricular? KNOW THE MECHANISM Fast, slow, premature, late, fib, flutter or blocked, paced

  28. Measure the PR Interval • Is the duration 0.12-0.20 seconds? • Is the interval consistent?

  29. Measure the Duration of the QRS Complex • Is the duration < 0.12 seconds? • Are all of the complexes the same size & shape? • Is there a QRS after each P wave?

  30. Checkpoint 1.The ECG provides information about: a. the contractility of the heart b. the electrical activity of the heart c. cardiac output and resistance d. all of the above 2. In the electrocardiogram, the QRS represents: a. ventricular contraction b. atrial contraction c. ventricular depolarization d. discharge of impulse from the sinus node 3. Indicate the intrinsic rate of the following: Sinus node Junctional tissue _______ Ventricular tissue

  31. Sinus Rhythms • Normal Sinus Rhythms (NSR) • Sinus Tachycardia (ST) • Sinus Bradycardia (SB) • Sinus Dysrhythmia (SD) • Sinus Pause (Sinus Arrest)

  32. Normal Sinus Rhythm The SA node (normal Pacemaker) of the heart is in control Rhythm: Regular Rate: 60-100/min P Wave Precedes each QRS, normal. PR: 0.12-0.20Sec QRS: < 0.12 sec & Constant

  33. Sinus Tachycardia SA node fires faster than 100/min Rhythm: Regular Rate: 100-160/min P Wave: Normal, precedes each QRS PR: 0.12 - 0.20 sec QRS: <0.12 sec

  34. Sinus Tachycardia Causes: * Anemia, Hypoxia, Hypovolemia, Hypotension * Exercise, Emotion, Anxiety, Pain * Fever * Drug related-Caffeine, Epinephrine, Cocaine * Early sign of CHF * Theophylline toxicity * Hyperthyroidism Management: * Assess for cause & treat it * Beta Blockers for primary tachycardia

  35. Sinus Bradycardia SA Node fires slower than 60/min Rhythm: Regular Rate: < 60/min P Wave: normal, precedes each QRS PR: 0.12 - 0.20 secQRS: < 0.12 sec

  36. Causes Normal in healthy, young, athletes Vagal stimulation… MI, Vomiting, Straining at stool, Pharyngeal suctioning Drug effect… Beta blockers Increased ICP Hypokalemia Sick Sinus syndrome Significance If severe or prolonged, may cause decrease in cardiac output and syncope At risk for escape rhythm and or premature beats to gain control due to long pauses Sinus Bradycardia

  37. Sinus Bradycardia Interventions Assess patient Hold digoxin, if digoxin toxicity Relieve source of vagal stimulation, if possible (treat nausea, shorten periods of suctioning, no valsalvas) May need to adjust drug regimen If symptomatic, treat with Atropine May require temporary pacemaker

  38. Sinus Dysrhythmia (Sinus Arrhythmia) Irregular heart rate; Sinus node in charge; usually varies with respiratory cycle Rhythm :IrregularRate :60 - 100 P wave : Normal PR :Normal QRS: Normal The longest R-R interval - the shortest R-R interval= > 0.12 seconds

  39. Sinus Dysrhythmia Significance: Usually none Causes: Common in children & outgrown in teens Variation of Sinus rhythm Vagal stimulation Treatment: Usually none R/O more serious irregular rhythm Minimize vagal stimulation

  40. Sinus Pause (Arrest) Sinus node fails to generate an impulse for one or more beats; usually reset by sinus node but escape beats/rhythms may occur Rhythm: Regular except for pause PR: normal Rate: depends on underlying rhythm QRS: normal No P wave preceding pause

  41. Sinus Pause • SIGNIFICANCE • Vagal stimulation • Sick Sinus syndrome • Dig. Toxicity • Beta blockers • Ca channel blockers • Ischemia of SA node • Pericarditis • Hyperkalema • Amiodarone INTERVENTIONS • Treat cause • Atropine for acute bradycardia • If asleep, wake the patient • Pause over 3 seconds… Evaluation for a pacemaker (External or permanent) CAUSES • May decrease CO • Duration of pause determines the seriousness of dysrhythmia

  42. Checkpoint True or False 1. Sinus dysrhythmia is dangerous and requires immediate intervention. 2. The treatment of choice for sinus tachycardia is related to the cause. 3. Sinus dysrhythmia is characterized by a slowing and speeding of the rate. 4. The first nursing action in relation to a rhythm disturbance is to check the patient and assess level of consciousness.

  43. Atrial Rhythms • Premature Atrial Complex (PAC) • Supraventricular Tachycardia (SVT) • Atrial Flutter • Atrial Fibrillation

  44. Premature Atrial Complexes • Originates outside the SA node • Single or multiple ectopic focus • Various shapes of P waves • PR - normal; QRS - normal

  45. PACs

  46. SVT ABSOLUTELY REGULAR RHYTHM ! USUALLY OCCURS SUDDENLY RATE: 160-240/min P WAVE: MAY NOT BE SEEN PR : NOT MEASURABLE QRS: NORMAL

  47. Significance - SVT • If rapid, can decrease cardiac output • Can cause • anxiety • angina • palpitations • shortness of breath • decreased level of consciousness • decreased BP • shock • pulmonary congestion • CHF • acute MI

  48. Causes - SVT

  49. Carotid Massage By MDs only! Both diagnose & terminate PSVT Auscultate first for bruit Never compress both carotids simultaneously!

  50. Cardioversion Synchronized cardioversion delivers electrical stimulus during depolarization - depolarizes all cells simultaneously, allowing SA node to resume the pacemaker role QRS complex must be present Usually elective Potassium, digoxin level,emergency equipment,O2, NPO, IV, TEE, Sedation

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