McCann Paramedic Program: Cardiology Lecture 2-EKG's

1. Cardiovascular Emergencies
Part II
Dale A. LeCrone Sr NRP
Instructor

2. • ECG monitor can be
used to:
• Monitor during
transport.
• Print strip for
dysrhythmia
interpretation.
• Print 12-lead ECG for
diagnosis.

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. • 12-lead ECG devices contain interpretation software.
• Use as only one party of assessment
• Some can transmit ECGs to receiving facility.

5. • Predetermined spots
• Usually adhesive with
gel center

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. • 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. • 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. • Limb leads (cont’d)
• For 12-lead ECG:
• White—right wrist
• Black—left wrist
• Red—left ankle
• Green—right ankle

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. • 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. • Precordial leads
• Six additional
electrodes on the
anterior chest

13. • Right-sided ECGs
• Used to evaluate the
electrical activity of the
right ventricle
• Precordial leads are
placed on the right
anterior thorax

14. • Posterior ECGs
• Evaluates left ventricle
posterior wall electrical
activity
• Three precordial leads
placed on left posterior
thorax

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. • 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

18. • 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

19. • Wave moves toward a positive electrode: deflection above baseline
• Wave moves toward a negative electrode: deflection below baseline

20. • 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)

21. • 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

23. • The ECG rhythm
components
correspond to electrical
events in the heart.

24. • P wave: represents atrial depolarization
• Smooth, round, upright shape
• Normal duration of less than 100 ms
• Amplitude less than 2.5 mm tall

25. • PR interval (PRI):
includes atrial
depolarization and
conduction of impulse
through AV junction
• Normal duration of 0.12
to 0.20 seconds

26. • 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

27. • QRS complex (cont’d)
• Q wave: First negative deflection
• R wave: First upward deflection
• S wave: Downward deflection after the R wave

28. • 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

29. • T wave: represents
ventricular
repolarization
• First half represents
absolute refractory
period (ARP)
• Second half represents
the relative refractory
period (RRP)

30. • 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

31. • Method to interpret dysrhythmias
• Identify the waves (P-QRS-T).
• Measure the PRI.
• Measure the QRS duration.
• Determine rhythm regularity.
• Measure the heart wave.

32. • Measure distance between R waves
• Regular: distance between R waves is the same

33. • Measure distance between R waves (cont’d)
• Irregularly irregular: no two R waves equal
• Regularly irregular: R waves are irregular but follow a pattern

34. • 6-second method
• Count the number of QRS complexes in a
6-second strip and multiply by 10.

35. • 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

36. • 1500 method
• Count the number of
small boxes between
any two QRS complexes.
• Divide by 1500.

37. • 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

38. • Dysrhythmia classifications
• Disturbances of automaticity or conduction
• Tachydysrhythmias or bradydysrhythmias
• Life threatening or non-life threatening
• By site from which they arise

39. • Normal sinus rhythm
• Intrinsic rate of 60 to 100 beats/min
• Upright P wave preceding each QRS complex

40. • Sinus bradycardia
• Rate of less than 60 beats/min
• Upright P wave preceding every QRS complex

41. • 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.

42. • Sinus tachycardia
• Rate is more than 100 beats/min.
• Upright P waves precede QRS complexes.

43. • Sinus tachycardia (cont’d)
• Hypoxia, metabolic alkalosis, hypokalemia, and hypocalcemia can lead to
electrical instability.
• Circus reentry may occur.

44. • Sinus dysrhythmia
• Slight variation in sinus rhythm cycling
• Upright P waves precede QRS complexes

45. • Sinus dysrhythmia (cont’d)
• More prominent with respiratory cycle fluctuation
• Increased filling pressures during inspiration stimulate Bainridge reflex
• Increase in BP stimulates baroreceptor reflex

46. • Sinus arrest
• SA node fails to initiate an impulse
• Upright P waves precede QRS complexes.

47. • 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.

48. • 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

49. • 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

50. • 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

51. • 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

52. • Atrial fibrillation
• Atria fibrillate or quiver
• Random depolarization from atria cells depolarizing independently

53. • Atrial fibrillation (cont’d)
• Irregularly irregular appearance
• Usually signs of serious heart problem
• Tendency to cause clots
• Prehospital treatment is rare.

54. • 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

55. • Supraventricular tachycardia (cont’d)
• Called paroxysmal SVT (PSVT) because of tendency to begin and end abruptly
• May greatly reduce CO

56. • Premature atrial complex
• A particular complex within another rhythm
• Upright P wave precedes each QRS complex

57. • 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

58. • 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)

59. • Wandering atrial pacemaker (cont’d)
• Most common with significant lung disease
• Treatment in the prehospital setting is not usually indicated.

60. • 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.

61. • Multifocal atrial tachycardia (cont’d)
• PR interval: 120 to 200 ms
• Most common with significant lung disease
• Therapies for SVT generally ineffective

62. • 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.

63. • 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

64. • 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.

65. • 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

66. • Junctional tachycardia
• Junctional rhythm rate higher than 100 beats/min
• Regular rhythm, little variation between
R-R intervals
• Seldom requires prehospital treatment

67. • 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

68. • 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.

69. • 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

70. • 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

71. • 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

72. • 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

73. • 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

74. • Idioventricular rhythm
• Occurs when SA and VA nodes fail
• May or may not result in a palpable pulse
• Treatment includes improving the CO.

75. • Accelerated idioventricular rhythm
• Occurs when idioventricular rhythm exceeds
40 beats/min but less than 100 beats/min
• Rarely treated in the prehospital setting

76. • Ventricular tachycardia
• Occurs when SA and AV nodes fail, and rate exceeds 100 beats/min
• QRS complexes usually have uniform tops and bottoms (monomorphic).

77. • Ventricular tachycardia (cont’d)
• Occasionally QRS complex will vary in height
• Torsades de pointes
• Requires treatment to maintain adequate CO

78. • 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

79. • Premature ventricular
complex (cont’d)
• Unifocal: from same
spot within ventricle
• Multifocal: two
premature complexes
with different
appearances

80. • 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

81. • 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

82. • Ventricular fibrillation
• Entire heart is fibrillating without organized contraction
• Occurs when many different heart cells become depolarized independently

83. • Ventricular fibrillation (cont’d)
• Coarse (early stages): chaotic wave height high
• Fine: great reduction in chaotic wave height

84. • Asystole (flat line)
• Entire heart no longer contracting
• Heart cells no longer have energy
• Complete absence of electrical activity

85. • Asystole (cont’d)
• Agonal rhythm: Flat baseline is interrupted by a small sinusoidal complex
• Generally considered a confirmation of death

86. • 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

87. • Newer pacemakers—sensors identify rate of spontaneous
depolarization
• Generate impulses when natural pacemakers have slowed

88. • 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