Cardio 2

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McCann Paramedic Program: Cardiology Lecture 2-EKG's

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Cardio 2

  1. 1. Cardiovascular Emergencies Part II Dale A. LeCrone Sr NRP Instructor
  2. 2. • ECG monitor can be used to: • Monitor during transport. • Print strip for dysrhythmia interpretation. • Print 12-lead ECG for diagnosis.
  3. 3. • Three standard limb leads (Leads I, II, and II) for continuous monitoring • 12-lead ECG provides detailed information about the heart’s conduction system • Records activity from 12 separate angles • Electrical “snapshot” of a part of the heart
  4. 4. • 12-lead ECG devices contain interpretation software. • Use as only one party of assessment • Some can transmit ECGs to receiving facility.
  5. 5. • Predetermined spots • Usually adhesive with gel center
  6. 6. • Basic principles: • It may be necessary to shave body hair. • Rub the site with an alcohol swab before application. • Attach the electrodes to the ECG cable before placement and confirm correct location. • Turn on the monitor, and print a sample strip.
  7. 7. • Artifacts can give false readings. • Straight line may indicate a loose or disconnected lead • Wavy baseline may be caused by movement or muscle tremor
  8. 8. • Limb leads (I, II, III, and aVR, aVL, aVF) • For continuous monitoring: • White—right upper chest near shoulder • Black—left upper chest near shoulder • Red—left lower abdomen • Green—right lower abdomen
  9. 9. • Limb leads (cont’d) • For 12-lead ECG: • White—right wrist • Black—left wrist • Red—left ankle • Green—right ankle
  10. 10. • Limb leads (cont’d) • Einthoven’s theory: Every time the heart contracts, electrical energy is emitted. • Lead I—between right and left arms • Lead II—between right arm and left leg • Lead III—between left arm and left leg
  11. 11. • Limb leads (cont’d) • Augmented violated (aV) leads created using four limb electrodes • Leads aVR, aVL, and aVF: combine two limb leads and use the other lead as the other pole.
  12. 12. • Precordial leads • Six additional electrodes on the anterior chest
  13. 13. • Right-sided ECGs • Used to evaluate the electrical activity of the right ventricle • Precordial leads are placed on the right anterior thorax
  14. 14. • Posterior ECGs • Evaluates left ventricle posterior wall electrical activity • Three precordial leads placed on left posterior thorax
  15. 15. • 15-lead ECG: standard 12-lead ECG plus leads V4R, V7, and V8. • Allows view of right ventricle and posterior wall of left ventricle • 18-lead ECG: standard tracing plus leads V4R through V6R and V7 through V9
  16. 16. • Unipolar versus bipolar leads • Leads I, II, III: bipolar leads containing positive and negative poles • Leads aVR, aVL, and aVF: unipolar leads • One true pole • Other end referenced against a combination of other leads
  17. 17. • Lead polarity • Bipolar leads have a negative and positive end. • Lead I: left arm is the positive terminal • Lead II: left leg is the positive terminal • Lead III: left leg is the positive terminal
  18. 18. • Wave moves toward a positive electrode: deflection above baseline • Wave moves toward a negative electrode: deflection below baseline
  19. 19. • Baseline represents electrically silent period in cardiac cycle • Perpendicular wave results in: • A perfectly flat line • A line with a positive and a negative component (biphasic waves)
  20. 20. • Graph paper moves past stylus at 25 mm/s • One 1-mm box — 0.04 seconds • One large box — 0.20 seconds • Vertical axis represents amplitude • Standard amplitude calibration — 10 mm/mV
  21. 21. • The ECG rhythm components correspond to electrical events in the heart.
  22. 22. • P wave: represents atrial depolarization • Smooth, round, upright shape • Normal duration of less than 100 ms • Amplitude less than 2.5 mm tall
  23. 23. • PR interval (PRI): includes atrial depolarization and conduction of impulse through AV junction • Normal duration of 0.12 to 0.20 seconds
  24. 24. • QRS complex: Three waveforms representing depolarization of two contracting ventricles • From beginning of Q wave to end of S wave • Sharp pointed waves, less than 120 ms • Indicates that impulse has proceeded normally
  25. 25. • QRS complex (cont’d) • Q wave: First negative deflection • R wave: First upward deflection • S wave: Downward deflection after the R wave
  26. 26. • J point: where QRS complex ends and ST segment begins • End of depolarization and beginning of repolarization • ST segment: begins at J point and ends at T wave
  27. 27. • T wave: represents ventricular repolarization • First half represents absolute refractory period (ARP) • Second half represents the relative refractory period (RRP)
  28. 28. • QT interval: represents all electrical activity of one completed ventricular cycle • Begins at onset of Q wave • Ends at the T wave • Normally lasts 360 to 440 ms
  29. 29. • Method to interpret dysrhythmias • Identify the waves (P-QRS-T). • Measure the PRI. • Measure the QRS duration. • Determine rhythm regularity. • Measure the heart wave.
  30. 30. • Measure distance between R waves • Regular: distance between R waves is the same
  31. 31. • Measure distance between R waves (cont’d) • Irregularly irregular: no two R waves equal • Regularly irregular: R waves are irregular but follow a pattern
  32. 32. • 6-second method • Count the number of QRS complexes in a 6-second strip and multiply by 10.
  33. 33. • Sequence method • Find R wave; count off above sequence until next R wave. • If interval spans fewer than three boxes, rate is greater than 100 • If more than five boxes, rate is less than 60
  34. 34. • 1500 method • Count the number of small boxes between any two QRS complexes. • Divide by 1500.
  35. 35. • Induced by many events • Flow of electricity through damaged or oxygen-deprived tissue may appear as irregularities • Many can be traced to ischemia • Most common cause of cardiac arrest
  36. 36. • Dysrhythmia classifications • Disturbances of automaticity or conduction • Tachydysrhythmias or bradydysrhythmias • Life threatening or non-life threatening • By site from which they arise
  37. 37. • Normal sinus rhythm • Intrinsic rate of 60 to 100 beats/min • Upright P wave preceding each QRS complex
  38. 38. • Sinus bradycardia • Rate of less than 60 beats/min • Upright P wave preceding every QRS complex
  39. 39. • Sinus bradycardia (cont’d) • Serious causes include: • SA node disease • AMI, which may stimulate vagal tone • Increased intracranial pressure • Use of beta blockers, calcium channel blockers, morphine, quinidine, or digitalis • Treatment focuses on tolerance and cause.
  40. 40. • Sinus tachycardia • Rate is more than 100 beats/min. • Upright P waves precede QRS complexes.
  41. 41. • Sinus tachycardia (cont’d) • Hypoxia, metabolic alkalosis, hypokalemia, and hypocalcemia can lead to electrical instability. • Circus reentry may occur.
  42. 42. • Sinus dysrhythmia • Slight variation in sinus rhythm cycling • Upright P waves precede QRS complexes
  43. 43. • Sinus dysrhythmia (cont’d) • More prominent with respiratory cycle fluctuation • Increased filling pressures during inspiration stimulate Bainridge reflex • Increase in BP stimulates baroreceptor reflex
  44. 44. • Sinus arrest • SA node fails to initiate an impulse • Upright P waves precede QRS complexes.
  45. 45. • Sinus arrest (cont’d) • Common causes: • Ischemia of the SA node • Increased vagal tone • Carotid sinus massage • Use of certain drugs • Treatment may include a pacemaker.
  46. 46. • Sick sinus syndrome (SSS) • Variety of rhythms, poorly functioning SA • It shows on an ECG as: • Sinus bradycardia • Sinus arrest • SA block • Alternating patterns of bradycardia and tachycardia
  47. 47. • Any atrial area may originate an impulse. • Rhythms have upright P waves preceding each QRS complex. • Not as well-rounded • Heart rates usually from 60 to 100 beats/min
  48. 48. • Atrial flutter • Atria contract too fast for ventricles to match • Resemble a saw tooth or picket fence • F waves get blocked by AV node, creating several F waves before each QRS complex
  49. 49. • Atrial flutter (cont’d) • Usually a sign of a serious heart problem • Treatment is usually medication or electrical cardioversion • Only done in field if condition is critical
  50. 50. • Atrial fibrillation • Atria fibrillate or quiver • Random depolarization from atria cells depolarizing independently
  51. 51. • Atrial fibrillation (cont’d) • Irregularly irregular appearance • Usually signs of serious heart problem • Tendency to cause clots • Prehospital treatment is rare.
  52. 52. • Supraventricular tachycardia (SVT) • Tachycardic rhythm from pacemaker • Regular rhythm, rate exceeding 150 beats/min • QRS complexes: 40 to 120 ms. • May have cannon “A” waves
  53. 53. • Supraventricular tachycardia (cont’d) • Called paroxysmal SVT (PSVT) because of tendency to begin and end abruptly • May greatly reduce CO
  54. 54. • Premature atrial complex • A particular complex within another rhythm • Upright P wave precedes each QRS complex
  55. 55. • Premature atrial complex (cont’d) • Non-conducted PAC: P wave occurs early on the ECG and is not followed by a QRS complex. • Can result from drugs or organic heart disease • Not treated in prehospital setting
  56. 56. • Wandering atrial pacemaker • Pacemaker moves from SA node to other areas • Upright P wave precedes each QRS (at least 3 shapes of P waves within a strip)
  57. 57. • Wandering atrial pacemaker (cont’d) • Most common with significant lung disease • Treatment in the prehospital setting is not usually indicated.
  58. 58. • Multifocal atrial tachycardia (MAT) • Pacemaker moves within various atrial areas • Rate of more than 100 beats/min • Upright P wave preceding each QRS complex • P waves vary.
  59. 59. • Multifocal atrial tachycardia (cont’d) • PR interval: 120 to 200 ms • Most common with significant lung disease • Therapies for SVT generally ineffective
  60. 60. • The AV node will take over if the SA node fails. • Rhythms of AV node origin are known as “junctional” rhythms • Have inverted or missing P waves • An impulse generated in the AV node travels down into the ventricles and up toward the SA node.
  61. 61. • Three possibilities: • Upside-down P wave immediately followed by QRS complex • Smaller P wave hidden within QRS complex • Inverted P wave after the QRS complex • Rates of 40 to 60 beats/min
  62. 62. • Junctional (escape) rhythm • Occur when SA node does not function • AV node becomes the pacemaker • Most common with significant SA node problems • Treatment is usually an implanted pacemaker.
  63. 63. • Accelerated junction rhythm • Present with rate exceeding 60 beats/min but less than 100 beats/min • Regular rhythm, little variation between R-R intervals • Seldom treated in the prehospital setting
  64. 64. • Junctional tachycardia • Junctional rhythm rate higher than 100 beats/min • Regular rhythm, little variation between R-R intervals • Seldom requires prehospital treatment
  65. 65. • Premature junctional complex • Particular complex within another rhythm • P wave will be inverted and upside down • PR interval: less than 120 ms • QRS complex: 40 to 120 ms • Rarely treated in the prehospital setting
  66. 66. • SA node initiates impulses resulting in heart contractions • Delayed when they reach AV node so atria can contract and fill the ventricle • Sometimes impulses are delayed longer than usual, causing heart blocks.
  67. 67. • First-degree heart block • Occurs when each impulse is delayed slightly longer than normal • Least serious type of block • Rarely treated in a prehospital setting
  68. 68. • Second-degree heart block: Mobitz type I (Wenckebach) • Occurs when each impulse is delayed a little longer, until an impulse cannot continue • P wave followed by P wave, followed by QRS complex with normal PR interval • Not treated in the prehospital setting
  69. 69. • Second-degree heart block: Mobitz type II (classical) • Occurs when several impulses cannot continue • Upright P wave precedes some QRS complexes, with an always constant PR interval • Only treated in the field if with bradycardia
  70. 70. • Third-degree heart block • Occurs when all impulses cannot continue, causing a QRS complex • Ventricles develop their own pacemaker. • Identified by nonconductor P waves • Treated in the field only if with bradycardia
  71. 71. • Ventricles may become the pacemaker if AV node does not take over after SA node fails • Wide QRS complexes and missing P waves • Impulses must travel cell by cell. • The impulses will travel more slowly. • Normally 20 to 40 beats/min
  72. 72. • Idioventricular rhythm • Occurs when SA and VA nodes fail • May or may not result in a palpable pulse • Treatment includes improving the CO.
  73. 73. • Accelerated idioventricular rhythm • Occurs when idioventricular rhythm exceeds 40 beats/min but less than 100 beats/min • Rarely treated in the prehospital setting
  74. 74. • Ventricular tachycardia • Occurs when SA and AV nodes fail, and rate exceeds 100 beats/min • QRS complexes usually have uniform tops and bottoms (monomorphic).
  75. 75. • Ventricular tachycardia (cont’d) • Occasionally QRS complex will vary in height • Torsades de pointes • Requires treatment to maintain adequate CO
  76. 76. • Premature ventricular complex (ectopic complex) • Particular complex within another rhythm • Occurs earlier than expected, causing a R-R interval between it and the previous complex
  77. 77. • Premature ventricular complex (cont’d) • Unifocal: from same spot within ventricle • Multifocal: two premature complexes with different appearances
  78. 78. • Premature ventricular complex (cont’d) • Couplet: Two complexes occurring together • Salvos: Three or more occurring in a row • Bigeminy: Salvos alternate with normal complex • Trigeminy: Third beat is a premature complex
  79. 79. • Premature ventricular complex (cont’d) • Usually from ischemia in ventricular tissue • May occur when ventricles are not fully repolarized, resulting in ventricular fibrillation • Rarely treated in the field
  80. 80. • Ventricular fibrillation • Entire heart is fibrillating without organized contraction • Occurs when many different heart cells become depolarized independently
  81. 81. • Ventricular fibrillation (cont’d) • Coarse (early stages): chaotic wave height high • Fine: great reduction in chaotic wave height
  82. 82. • Asystole (flat line) • Entire heart no longer contracting • Heart cells no longer have energy • Complete absence of electrical activity
  83. 83. • Asystole (cont’d) • Agonal rhythm: Flat baseline is interrupted by a small sinusoidal complex • Generally considered a confirmation of death
  84. 84. • Ventricular pacemaker: attached to ventricles • Spike followed by a wide QRS complex • Another is attached to atria and ventricle • Spike followed by a P wave and another spike followed by a wide QRS complex
  85. 85. • Newer pacemakers—sensors identify rate of spontaneous depolarization • Generate impulses when natural pacemakers have slowed
  86. 86. • If pacemaker is failing, spikes will be visible but not followed by a QRS complex. • “Loss of capture” • Patients need TCP as quickly as possible. • May fail because of a “runaway” pacemaker

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