Chapter 4. Atrial Rhythms

Transcription

1 Chapter 4 Atrial Rhythms 1

2 Objectives Explain the concepts of altered automaticity, triggered activity, and reentry. Explain the terms bigeminy, trigeminy, quadrigeminy, and run when used to describe premature complexes. Describe the ECG characteristics, possible causes, signs and symptoms, and initial emergency care for premature atrial complexes (PACs). Explain the difference between a compensatory and noncompensatory pause. Explain the terms wandering atrial pacemaker and multifocal atrial tachycardia. Describe the ECG characteristics, possible causes, signs and symptoms, and initial emergency care for wandering atrial pacemaker (multiformed atrial rhythm). 2

3 Objectives Describe the ECG characteristics, possible causes, signs and symptoms, and initial emergency care for multifocal atrial tachycardia (MAT). Describe the ECG characteristics, possible causes, signs and symptoms, and initial emergency care for atrial tachycardia (AT). Discuss preexcitation syndrome and name its three major forms. Explain the terms paroxysmal atrial tachycardia (PAT) and paroxysmal supraventricular tachycardia (PSVT). List four examples of vagal maneuvers. Discuss the indications and procedure for synchronized cardioversion. 3

4 Objectives Describe the ECG characteristics, possible causes, signs and symptoms, and initial emergency care for atrioventricular nodal reentrant tachycardia (AVNRT). Describe the ECG characteristics, possible causes, signs and symptoms, and initial emergency care for atrioventricular reentrant tachycardia (AVRT). Describe the ECG characteristics, possible causes, signs and symptoms, and initial emergency care for atrial flutter. Describe the ECG characteristics, possible causes, signs and symptoms, and initial emergency care for atrial fibrillation (AFib). 4

5 Introduction Atria Thin-walled, lowpressure chambers Receive blood from systemic circulation and lungs Atrial kick 5

6 Atrial Dysrhythmias: Mechanisms Atrial dysrhythmias reflect abnormal electrical impulse formation and conduction in the atria. 6

7 Atrial Dysrhythmias: Mechanisms Atrial dysrhythmias may occur because of: Altered automaticity Triggered activity Reentry Altered automaticity and triggered activity are disorders in impulse formation Reentry is a disorder in impulse conduction 7

8 Altered Automaticity Can occur in: Normal pacemaker cells Myocardial working cells that do not normally function as pacemaker sites These cells depolarize and initiate impulses before a normal impulse 8

9 Triggered Activity Results from abnormal electrical impulses that sometimes occur during repolarization (afterdepolarizations), when cells are normally quiet Requires a stimulus to initiate depolarization 9

10 Reentry (Reactivation) A condition in which an impulse returns to stimulate tissue that was previously depolarized 10

11 Reentry (Reactivation) Reentry requires: A potential conduction circuit or circular conduction pathway A block within part of the circuit Delayed conduction with the remainder of the circuit 11

12 Reentry (Reactivation) Reentry results in a single premature beat or repetitive electrical impulses resulting in short periods of rapid rhythms 12

13 Atrial Dysrhythmias Most atrial dysrhythmias are not lifethreatening Some are associated with extremely fast ventricular rates An excessively rapid heart rate may compromise cardiac output 13

14 Premature Complexes Premature beats may be produced by: Atria AV junction Ventricles Premature beats appear early, that is, they occur before the next expected beat 14

15 Premature Complexes Premature beats are identified by their site of origin Premature atrial complexes (PACs) Premature junctional complexes (PJCs) Premature ventricular complexes (PVCs) 15

16 Premature Complexes Patterns Pairs (coupled) Two premature beats in a row Runs or bursts Three or more premature beats in a row Bigeminy Every other beat is a premature beat Trigeminy Every third beat is a premature beat Quadrigeminy Every fourth beat is a premature beat 16

17 Premature Atrial Complexes Occur when an irritable site within the atria discharges before the next SA node impulse is due to discharge The P wave of a PAC may be: Biphasic (partly positive, partly negative) Flattened Notched Pointed Lost in the preceding T wave 17

18 PACs How Do I Recognize Them? Rate Rhythm Usually within normal range, but depends on underlying rhythm Regular with premature beats 18

19 PACs How Do I Recognize Them? S = SA node; = atrial beat P waves Premature (occurring earlier than the next expected sinus P wave), positive (upright) in lead II, one before each QRS complex, often differ in shape from sinus P waves may be flattened, notched, pointed, biphasic, or lost in the preceding T wave 19

20 PACs How Do I Recognize Them? PR interval QRS duration May be normal or prolonged depending on the prematurity of the beat Usually 0.10 sec or less but may be wide (aberrant) or absent, depending on the prematurity of the beat; the QRS of the PAC is similar in shape to those of the underlying rhythm unless the PAC is abnormally conducted 20

21 PACs How Do I Recognize Them? Sinus tachycardia at 111 bpm with three PACs 21

22 PACs How Do I Recognize Them? Rate Rhythm P waves PR interval QRS duration Usually within normal range, but depends on underlying rhythm Regular with premature beats Premature (occurring earlier than the next expected sinus P wave), positive (upright) in lead II, one before each QRS complex, often differ in shape from sinus P waves may be flattened, notched, pointed, biphasic, or lost in the preceding T wave May be normal or prolonged depending on the prematurity of the beat Usually 0.10 sec or less but may be wide (aberrant) or absent, depending on the prematurity of the beat; the QRS of the PAC is similar in shape to those of the underlying rhythm unless the PAC is abnormally conducted 22

23 Compensatory/Noncompensatory Pause A noncompensatory (incomplete) pause often follows a PAC Represents the delay during which the SA node resets its rhythm for the next beat 23

24 Compensatory/Noncompensatory Pause To determine whether a pause following a premature complex is compensatory or noncompensatory: Measure the distance between three normal beats Compare that distance between three beats, one of which includes the premature complex 24

25 Compensatory/Noncompensatory Pause The pause is termed noncompensatory (incomplete) if the normal beat following the premature complex occurs before it was expected When the distance is NOT the same The pause is compensatory (complete) if the normal beat following the premature complex occurs when expected When the distance is the same 25

26 Aberrantly Conducted PACs PACs associated with a wide QRS complex are called aberrantly conducted PACs Indicates conduction through ventricles is abnormal 26

27 Nonconducted PACs A PAC may occur very prematurely and close to the T wave of the preceding beat Only a P wave may be seen with no QRS after it (appearing as a pause) This is a nonconducted or blocked PAC P wave occurred too early to be conducted 27

28 PACs What Causes Them? Emotional stress Congestive heart failure Acute coronary syndromes Mental and physical fatigue Atrial enlargement Digitalis toxicity Valvular heart disease Electrolyte imbalance Hyperthyroidism Stimulants: caffeine, tobacco, cocaine 28

29 PACs What Do I Do About Them? Occasional PACs usually do not require treatment Frequent PACs may initiate episodes of atrial fibrillation, atrial flutter, or PSVT Frequent PACs are treated by correcting the underlying cause: Stress reduction Reduced consumption of caffeine-containing beverages Treatment of congestive heart failure Correction of electrolyte imbalance 29

30 Wandering Atrial Pacemaker Multiformed atrial rhythm Updated term for the rhythm formerly known as wandering atrial pacemaker Size, shape, and direction of P waves vary 30

31 Wandering Atrial Pacemaker How Do I Recognize It? Rate Usually bpm, but may be slow. If the rate is more than 100 bpm, the rhythm is termed multifocal (or chaotic) atrial tachycardia Rhythm May be irregular as pacemaker site shifts from SA node to ectopic atrial locations and AV junction 31

32 Wandering Atrial Pacemaker How Do I Recognize It? P Waves PR Interval QRS Size, shape, and direction may change from beat to beat Variable Usually 0.10 sec or less unless an intraventricular conduction delay exists 32

33 Wandering Atrial Pacemaker How Do I Recognize It? Rate Rhythm P Waves PR Interval QRS Usually bpm, but may be slow. If the rate is greater than 100 bpm, the rhythm is termed multifocal (or chaotic) atrial tachycardia. May be irregular as the pacemaker site shifts from the SA node to ectopic atrial locations and the AV junction Size, shape, and direction may change from beat to beat. At least three different P wave configurations (seen in the same lead) are required for a diagnosis of wandering atrial pacemaker or multifocal atrial tachycardia. Variable Usually 0.10 sec or less unless an intraventricular conduction delay exists 33

34 Wandering Atrial Pacemaker What Causes It? May be observed in normal, healthy hearts (particularly in athletes) and during sleep May also occur with some types of organic heart disease and with digitalis toxicity 34

35 Wandering Atrial Pacemaker What Do I Do About It? Usually produces no signs and symptoms unless associated with a slow rate If the rhythm occurs because of digitalis toxicity, the drug should be withheld 35

36 Multifocal Atrial Tachycardia How Do I Recognize It? When wandering atrial pacemaker is associated with a ventricular rate greater than 100 bpm, the rhythm is called multifocal atrial tachycardia (MAT) or chaotic atrial tachycardia 36

37 Multifocal Atrial Tachycardia Most often seen in: Severe COPD Hypoxia What Causes It? Acute coronary syndromes Digoxin toxicity Rheumatic heart disease Theophylline toxicity Electrolyte imbalances Hypokalemia Hypomagnesemia 37

38 Multifocal Atrial Tachycardia What Do I Do About It? Treatment is directed at the underlying cause If patient is symptomatic but you are uncertain rhythm is MAT: Vagal maneuvers, adenosine If you know the rhythm is MAT and the patient is symptomatic, consult cardiologist 38

39 Vagal Maneuvers Coughing Squatting Breath-holding Carotid sinus massage Application of a cold stimulus to the face Valsalva s maneuver Gagging 39

40 Carotid Sinus Massage 40

41 Carotid Sinus Massage 41

42 Carotid Sinus Massage 42

43 Adenosine Can interrupt reentry pathways that involve the AV node Rapid onset of action Short half-life 43

44 Supraventricular Arrhythmias Begin above the bifurcation of the bundle of His Includes rhythms that begin in the: SA node Atrial tissue AV junction 44

45 Types of Supraventricular Tachycardias 45

46 Atrial Tachycardia Atrial tachycardia is a series of rapid beats from an atrial ectopic focus This rapid atrial rate overrides the SA node and becomes the pacemaker 46

47 Atrial Tachycardia Atrial tachycardia 3 or more PACs in a row at a rate of more than 100 bpm Paroxysmal atrial tachycardia (PAT) Atrial tachycardia that starts or ends suddenly 47

48 Atrial Tachycardia 48

49 Atrial Tachycardia How Do I Recognize It? Atrial tachycardia is shown that ends spontaneously with the abrupt resumption of sinus rhythm. The P waves of the tachycardia (rate: about 150 bpm) are superimposed on the preceding T waves. 49

50 Atrial Tachycardia How Do I Recognize It? Rate Rhythm P Waves PR Interval QRS bpm Regular One P wave precedes each QRS complex in lead II; P waves differ in shape from sinus P waves; an isoelectric baseline is usually present between P waves; if the atrial rhythm originates in the low portion of the atrium, P waves will be negative in lead II. With rapid rates, it is difficult to distinguish P waves from T waves May be shorter or longer than normal 0.10 sec or less unless an intraventricular conduction delay exists 50

51 Atrial Tachycardia Paroxysmal atrial tachycardia with block 51

52 Stimulant use Atrial Tachycardia What Causes It? Caffeine, albuterol, theophylline, cocaine Infection Electrolyte imbalance Acute illness with excessive catecholamine release Myocardial infarction 52

53 Atrial Tachycardia What Do I Do About It? Possible signs and symptoms: Asymptomatic Palpitations Fluttering sensation in the chest Chest pressure Dyspnea Fatigue Dizziness or lightheadedness Syncope or near-syncope 53

54 Atrial Tachycardia What Do I Do About It? If symptomatic due to rapid rate: Vagal maneuvers Adenosine drug of choice Calcium channel blockers Beta-blockers Amiodarone 54

55 Amiodarone Coronary and peripheral vasodilator Suppresses SA node function Prolongs PR, QRS, and QT intervals Slows conduction at the AV junction 55

56 Amiodarone Hypotension and bradycardia most common adverse effects Slow infusion rate or discontinue if seen Additive effect with other medications that prolong the QT interval 56

57 Synchronized Cardioversion Delivery of an electrical shock to the heart timed to occur during QRS 57

58 Cardioversion Indications Tachycardias (except sinus tachycardia) with a ventricular rate greater than 150 bpm that have a clearly identifiable QRS complex (such as some narrow QRS tachycardias and ventricular tachycardia) 58

59 Cardioversion Procedure 59

60 Cardioversion Procedure 60

61 Cardioversion Procedure 61

62 Cardioversion Procedure 62

63 Cardioversion Procedure 63

64 Cardioversion Procedure 64

65 AV Nodal Reentrant Tachycardia (AVNRT) Most common type of SVT Caused by reentry in the area of the AV node 65

66 AVNRT How Do I Recognize It? AVNRT is usually precipitated by a PAC Electrical circuit allows impulse to spin around in a circle Results in a very rapid and regular rhythm Rate: bpm 66

67 AVNRT How Do I Recognize It? 67

68 AVNRT How Do I Recognize It? Rate Rhythm P Waves PR Interval QRS bpm (usually 180 to 200 bpm in adults) Regular Usually not identifiable; P wave usually hidden in T wave of preceding beat Not measurable 0.10 sec or less unless an intraventricular conduction delay exists 68

69 Paroxysmal Supraventricular Tachycardia (PSVT) Regular, narrow-qrs tachycardia that starts or ends suddenly P waves usually hidden in T waves of preceding beats 69

70 AVNRT What Causes It? Common in individuals with no structural heart disease Triggers: Hypoxia Stress Anxiety Caffeine Smoking Sleep deprivation Many medications 70

71 AVNRT What Causes It? AVNRT also occurs in individuals with: COPD Coronary artery disease Valvular heart disease Congestive heart failure Digitalis toxicity 71

72 AVNRT What Do I Do About It? Possible signs and symptoms: Palpitations (common) Lightheadedness Neck vein pulsations Syncope or nearsyncope Dyspnea Weakness Nervousness, anxiety Chest pain or pressure Signs of shock Congestive heart failure 72

73 Stable patient AVNRT What Do I Do About It? Oxygen, IV access, cardiac monitor Vagal maneuvers Adenosine 73

74 AVNRT What Do I Do About It? If the patient is unstable: Oxygen, IV access, cardiac monitor Consider medication administration Consider sedation If the patient is awake and time permits Synchronized cardioversion 74

75 AV Reentrant Tachycardia (AVRT) Atrioventricular reentry tachycardia (AVRT) involves a pathway of impulse conduction outside the AV node and bundle of His 75

76 AV Reentrant Tachycardia Preexcitation (AVRT) Impulse begins above the ventricles but travels via a pathway other than AV node and bundle of His Supraventricular impulse excites the ventricles earlier than normal 76

77 AV Reentrant Tachycardia (AVRT) 77

78 WPW How Do I Recognize It? Short PR interval Delta wave QRS widening Secondary ST segment and T wave changes 78

79 WPW How Do I Recognize It? 79

80 WPW How Do I Recognize It? Rate Rhythm P Waves PR Interval QRS Usually bpm, if the underlying rhythm is sinus in origin Regular, unless associated with atrial fibrillation Normal and positive in lead II unless WPW is associated with atrial fibrillation If P waves are observed, less than 0.12 sec Usually greater than 0.12 second; slurred upstroke of the QRS complex (delta wave) may be seen in one or more leads 80

81 AVRT Three main types of tachydysrhythmias that occur in WPW: AVRT (most common) Atrial fibrillation Atrial flutter 81

82 WPW What Causes It? Common cause of tachydysrhythmias in infants and children Accessory pathway in WPW is likely to be congenital in origin 82

83 AVRT What Do I Do About It? Common signs and symptoms associated with AVRT: Palpitations Lightheadedness Shortness of breath Anxiety Weakness Dizziness Chest discomfort Signs of shock 83

84 AVRT What Do I Do About It? Consultation with a cardiologist is recommended Stable but symptomatic patient Oxygen, IV access, and IV medications such as amiodarone Unstable patient Synchronized cardioversion 84

85 Atrial Flutter Ectopic atrial rhythm in which an irritable site fires regularly at an extremely rapid rate Type I atrial flutter Type II atrial flutter 85

86 Atrial Flutter How Do I Recognize It? Atrial flutter with 2:1 conduction Atrial flutter with 4:1 conduction 86

87 Atrial Flutter How Do I Recognize It? Rate Rhythm P Waves PR Interval QRS Atrial rate bpm, typically 300 bpm; ventricular rate variable determined by AV blockade; ventricular rate will usually not exceed 180 bpm due to intrinsic conduction rate of AV junction Atrial regular, ventricular regular or irregular depending on AV conduction/blockade No identifiable P waves; saw-toothed flutter waves are present Not measurable 0.10 sec or less but may be widened if flutter waves are buried in the QRS complex or an intraventricular conduction delay exists 87

88 Atrial Flutter What Causes It? Atrial flutter is usually a paroxysmal rhythm precipitated by a PAC May last for seconds to hours and occasionally lasts 24 hours or more Chronic atrial flutter is unusual Rhythm usually converts to sinus rhythm or atrial fibrillation, on its own or with treatment 88

89 Conditions Associated with Atrial Flutter Hypoxia Pulmonary embolism Chronic lung disease Mitral or tricuspid valve stenosis or regurgitation Pneumonia Complication of myocardial infarction Ischemic heart disease Cardiomyopathy Hyperthyroidism Digitalis or quinidine toxicity Cardiac surgery Pericarditis/myoca rditis 89

90 Atrial Flutter What Do I Do About It? Cardiologist consult recommended If rapid ventricular rate, control ventricular response If rapid ventricular rate and serious signs and symptoms, synchronized cardioversion 90

91 Atrial Fibrillation (AFib) 91

92 Atrial Fibrillation How Do I Recognize It? 92

93 Atrial Fibrillation How Do I Recognize It? AFib can occur with complete AV block Ventricular rhythm will be slow and regular 93

94 Atrial Fibrillation How Do I Recognize It? Rate Rhythm P Waves PR Interval QRS Atrial rate usually bpm; ventricular rate variable Ventricular rhythm usually irregularly irregular No identifiable P waves, fibrillatory waves present; erratic, wavy baseline Not measurable 0.10 sec or less but may be widened if an intraventricular conduction delay exists 94

95 Atrial Fibrillation What Causes It? Can occur in patients with or without detectable heart disease or related symptoms Increased stroke risk Atria do not contract effectively Blood pools within the atria, forming clots Clot dislodges and moves to artery in the brain 95

96 Conditions Associated with Atrial Fibrillation Idiopathic (no clear cause) Hypertension Ischemic heart disease Advanced age Rheumatic heart disease Cardiomyopathy Congestive heart failure Congenital heart disease Sick sinus syndrome WPW syndrome Pericarditis Pulmonary embolism Chronic lung disease After surgery Diabetes Stress Sympathomimetics Excessive caffeine Hypoxia Hypokalemia Hypoglycemia Systemic infection Hyperthyroidism Electrocution 96

97 Atrial Fibrillation What Do I Do About It? Cardiologist consult recommended If rapid ventricular rate, control ventricular response If rapid ventricular rate and serious signs and symptoms, synchronized cardioversion Anticoagulation recommended if AFib has been present for 48 hours or longer 97

98 Questions? 98