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Chapter_36 dysrhythmias [Autosaved].pptx

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Chapter_36 dysrhythmias [Autosaved].pptx

  1. NURSING MANAGEMENT DYSRHYTHMIAS Chapter 36 This chapter describes basic principles of electrocardiographic monitoring and recognition and treatment of common dysrhythmias. In addition, it presents ECG changes that are associated with acute coronary syndrome (ACS).
  2. OBJECTIVES 1. Examine the nursing management of patients requiring continuous electrocardiographic (ECG) monitoring. 2. Differentiate the clinical characteristics and ECG patterns of normal sinus rhythm, common dysrhythmias, and acute coronary syndrome (ACS). 3. Compare the nursing and collaborative management of patients with common dysrhythmias and ECG changes associated with ACS. 4. Differentiate between defibrillation and cardioversion, including indications for use and physiologic effects. 5. Describe the management of patients with pacemakers and implantable cardioverter-defibrillators. 6. Select appropriate interventions for patients undergoing electrophysiologic testing and radiofrequency catheter ablation therapy
  3. KeyTerms  asystole, p. 795  atrial fibrillation, p. 796  atrial flutter, p. 795  automatic external defibrillator (AED), p. 802  cardiac pacemaker, p. 803  complete heart block, p. 798  dysrhythmias, p. 787  premature atrial contraction (PAC), p. 794  premature ventricular contraction (PVC), p. 799  telemetry monitoring, p. 790  ventricular fibrillation (VF), p. 800  ventricular tachycardia (VT),  atrial systole  bundle of His  Cardiac cycle
  4. Dysrhythmia  (also called arrhythmia) is an abnormal or irregular heartbeat.  An abnormal heart rate means that your heart rate is either too fast (typically over 100 beats per minute) or too slow (typically below 60 beats per minute).  On the other hand, an irregular heartbeat means that your heart’s rhythm is disrupted in some way.  For instance, the electrical signal that controls your heartbeat might be interrupted due to scar tissue in the heart.  Or, the electrical signal might start too soon and give you the feeling of your heart skipping a beat. In that case, you’ll notice a stronger heartbeat right after the brief pause. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  5. Cardiac Conduction System  The heart’s electrical conduction system initiates an impulse whose purpose is to stimulate the mechanical cells of the heart to contract.  A normal cardiac impulse begins in the sinoatrial (SA) node in the upper right atrium.  It spreads over the atrial myocardium via interatrial and internodal pathways, causing atrial contraction.  The impulse then travels to the atrioventricular (AV) node, through the bundle of His, and down the left and right bundle branches.  It ends in the Purkinje fibers, which transmit the impulse to the ventricles. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  6. PROPERTIES OF CARDIAC CELLS Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 6
  7. Cardiac Cycle  A cardiac cycle is the period from the beginning of one heartbeat to the beginning of the next.  The cardiac cycle is the electrical representation of the impulse that stimulates contraction and relaxation of the atria and ventricles.  Within the normal cardiac cycle, there is a P wave, a QRS complex, and a T wave Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 7
  8. Nervous Control of the Heart  Stimulation of the vagus nerve causes a decreased rate of firing of the SA node and slowed impulse conduction of the AV node.  Stimulation of the sympathetic nerves increases SA node firing, AV node impulse conduction, and cardiac contractility. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  9. ELECTROCARDIOGRAM  The electrocardiogram (ECG) is a graphic tracing of the electrical impulses produced in the heart.  The electrical activity of the heart is seen either with an ECG that shows the activity for that moment when the ECG is obtained or with continuous cardiac monitoring.  Electrodes placed on the patient’s skin allow various views of the heart’s electrical activity to be seen.  Each view of the heart is referred to as a lead.  A 12-lead ECG provides 12 different views of the heart’s electrical activity, 9
  10. Electrocardiogram Graph Paper  ECG paper consists of large (heavy lines) and small (light lines) squares.  Each large square consists of 25 smaller squares (five horizontal and five vertical).  Horizontally, each small square (1 mm) represents 0.04 second.  This means that one large square equals 0.20 second and that 300 large squares equal 1 minute.  Vertically, each small square (1 mm) represents 0.1 millivolt (mV). This means that one large square equals 0.5 mV. 10
  11. THE ECG LEADS  The ECG has 12 recording leads.  Six of the leads measure electrical forces in the frontal plane.  The remaining six unipolar leads (V1 throughV6) measure the electrical forces in the horizontal plane (precordial leads).  The 12-lead ECG may show changes suggesting structural changes, conduction disturbances, damage (e.g., ischemia, infarction), electrolyte imbalance, or drug toxicity.  Obtaining 12 ECG views of the heart is also helpful in the assessment of dysrhythmias. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 11
  12. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  13. INTERPRETATION OF CARDIAC RHYTHMS  Six-Step Process for Dysrhythmia Interpretation  A 6-second ECG tracing is used when interpreting rhythms  Step 1. Regularity of the Rhythm  Step 2. Heart Rate  Step 3. P Waves  Step 4. PR Interval  Step 5. QRS Interval  Step 6. QT Interval Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 13
  14. INTERPRETATION OF CARDIAC RHYTHMS Regularity of the Rhythm  The regularity of the rhythm can be determined by looking at the R-to-R spacing on the ECG.  Count the number of small squares between each R wave, which normally should remain the same. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 14
  15. INTERPRETATION OF CARDIAC RHYTHMS  Step 2. Heart Rate  1. Count the number of small (0.04-second) squares between two R waves and divide that number into 1500. This gives the beats per minute, because 1500 small squares equals 1 minute  This method is used only for regular rhythms and is very accurate.  2. Six-second method: the 6-second method is used for irregular rhythms. Count the number of R waves in a 6- second strip and multiply the total by 10. Inc., an affiliate of Elsevier Inc. 15
  16. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  17. INTERPRETATION OF CARDIAC RHYTHMS  Step 3. PWaves  The P waves on the ECG tracing are examined to see if (1) there is one P wave in front of every QRS,  (2) the P waves are regularly occurring, and (3) the P waves all look alike Inc., an affiliate of Elsevier Inc. 17
  18. INTERPRETATION OF CARDIAC RHYTHMS  Step 4. PR Interval  All PR intervals are measured to determine whether they are normal (0.12–0.20 seconds) and constant. Inc., an affiliate of Elsevier Inc. 18
  19. INTERPRETATION OF CARDIAC RHYTHMS Inc., an affiliate of Elsevier Inc. 19 The QRS intervals are measured to determine whether they are all within normal range (0.06–0.10 seconds).
  20. INTERPRETATION OF CARDIAC RHYTHMS Inc., an affiliate of Elsevier Inc. 20 Step 6. QT Interval  The QT interval is measured from the onset of the QRS complex to the end of the T wave.  QT interval represents the duration of ventricular electrical systole, which includes ventricular activation and recovery.  excessive extension of the QT interval is strongly associated with ventricular arrhythmias including Torsade de Pointes (TdP), an acceleration in cardiac rhythm that can lead to heart attack.
  21. NORMAL SINUS RHYTHM  Normal sinus rhythm (NSR) is the heart’s normal rhythm  It originates in the SA node and has complete, regular cardiac cycles at 60 to 100 bpm.  NORMAL SINUS RHYTHM RULES  1. Rhythm: regular  2. Heart rate: 60 to 100 bpm  3. P waves: rounded, upright, precede each QRS  complex, alike  4. PR interval: 0.12 to 0.20 seconds  5. QRS interval: less than or equal to 0.10 seconds. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  22. DYSRHYTHMIAS  Two terms are used for rhythm disturbances: arrhythmia (irregularity or loss of rhythm of the heartbeat) and dysrhythmia (abnormal, disordered, or disturbed rhythm).  Several mechanisms can cause a dysrhythmia. Examples:  disturbance in the formation of an impulse  the impulse may arise from the atria, the AV node, or the ventricles rather than the SA node.  May lead to an increased or decreased heart rate, early or late beats, or atrial or ventricular fibrillation disturbance in the conduction of the impulse.  there may be normal formation of the impulse, but it becomes blocked within the electrical conduction.  system, resulting in abnormal conduction (as in heart block or bundle branch blocks). Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  23. Dysrhythmias Originating in the Sinoatrial Node  Rhythms arising from the SA node are referred to as sinus rhythms  Disturbances in conduction from the SA node can cause irregular rhythms or abnormal heart rates  Sinus Bradycardia  SinusTachycardia Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 23
  24. Dysrhythmias Originating in the Sinoatrial Node  Sinus Bradycardia  the conduction pathway is the same as that in sinus rhythm  the SA node fires at a rate less than 60 beats/minute  May be a normal in aerobically trained athletes and in some people during sleep  also occurs in response to carotid sinus massage, Valsalva maneuver, hypothermia, vagal stimulation, and administration of certain drugs (e.g., β-adrenergic blockers, calcium channel blockers, Digoxin). Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 24
  25. Sinus Bradycardia  SIGNS AND SYMPTOMS.  Usually, asymptomatic  With symptomatic bradycardia:  decreased BP, respiratory distress, diminished or absent peripheral pulses, fatigue, or syncope can occur.  Treatment can include intravenous (IV) atropine, or infusions of dopamine or epinephrine. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 25
  26. Sinus Tachycardia  a heart rate greater than 100 bpm that originates from the SA node.  Has the same components as NSR except the rate is faster  ETIOLOGY.  physical activity; hemorrhage; shock; medications such as epinephrine, atropine, or nitrates; dehydration; fever; MI; electrolyte imbalance; fear; and anxiety.  Tachycardia occurs as a compensatory mechanism for hypoxia when additional cardiac output is needed to deliver oxygen to tissues. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 26
  27. Sinus Tachycardia  SIGNS AND SYMPTOMS.  can be asymptomatic.  But if the rate is very rapid (usually >150 bpm) and sustained for long periods, the patient may experience angina, dyspnea, syncope, or tachypnea.  THERAPEUTIC MEASURES.  If stable, obtain an ECG and treat the cause.  Medications such as adenosine, calcium channel blockers, or beta blockers can be used to slow the heart rate Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 27
  28. Dysrhythmias Originating in the Atria  The SA node is the primary pacemaker, but if the atria initiate impulses faster than the SA node, they become the primary pacemaker.  Atrial rhythms are usually faster than 100 bpm and can exceed 200 bpm.  When an impulse originates outside the SA node, the P waves produced look different (flatter, notched, or peaked) from the rounded P waves from the SA node.  This indicates that the SA node is not controlling the heart rate.  These atrial impulses travel to the ventricles to initiate a normal QRS complex after each P wave. 28
  29. Dysrhythmias Originating in the Atria  Atrial Fibrillation  ETIOLOGY.  aging (increases after age 60 and is the most common sustained dysrhythmia)  History of cigarette smoking,  rheumatic or ischemic heart diseases,  heart failure,  hypertension,  pericarditis,  pulmonary embolism,  And some medications. 29
  30. Atrial Fibrillation  1. Rhythm: irregularly irregular  2. Heart rate: atrial rate not measurable; ventricular rate under 100 is controlled response; greater than 100 is rapid ventricular response  3. P waves: no identifiable P waves  4. PR interval: none can be measured because no P waves are seen  5. QRS interval: less than or equal to 0.10 seconds. 30
  31. Atrial Fibrillation  SIGNS AND SYMPTOMS.  most patients feel the irregular rhythm.  Many describe it as palpitations or a skipping heartbeat.  A patient’s radial pulse may be faint because of a decreased stroke volume  If the ventricular rhythm is rapid and sustained, the patient can go into left-sided heart failure. 31
  32. Atrial Fibrillation  THERAPEUTIC MEASURES.  The focus of AF treatment is to control rate, prevent thromboembolism, and restore normal rhythm.  If the patient is unstable, synchronized cardioversion is done immediately to try to return the heart to NSR.  For the patient who is stable, medications to control the ventricular rate such as beta blockers, calcium channel blockers, or digoxin are used.  Anticoagulant therapy is given to reduce thrombi, which can cause a stroke. 32
  33. Paroxysmal SupraventricularTachycardia. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  34. Ventricular Dysrhythmias PREMATURE VENTRICULAR CONTRACTION  Premature ventricular contractions (PVCs) originate in the ventricles from an ectopic focus (a site other than the SA node).  The ventricles are irritable and fire prematurely, before the SA node does.  When the ventricles fire first, the impulses are not conducted normally through the electrical pathway.  This results in a wide (>0.10 seconds), bizarre QRS complex on an ECG.  SIGNS AND SYMPTOMS.  PVCs may be felt by the patient and are described as a skipped beat or palpitations. With frequent PVCs, cardiac output can be decreased, leading to fatigue, dizziness, or more severe 34
  35. Ventricular Dysrhythmias PREMATURE VENTRICULAR CONTRACTION  THERAPEUTIC MEASURES.  Occasional PVCs do not usually require treatment.  However, if the PVCs are more than six per minute, regularly occurring, multifocal, falling on the T wave (known as “R-on-T phenomenon,” which can trigger life-threatening dysrhythmias),  Or caused by an acute MI, they can be dangerous. Antidysrhythmic.  drugs that depress myocardial activity are used to treat PVCs such as amiodarone and beta blockers 35
  36. Ventricular Dysrhythmias Ventricular Tachycardia  The occurrence of three or more PVCs in a row is referred to as ventricular tachycardia (VT)  VT results from the continuous firing of an ectopic ventricular focus.  During VT, the ventricles rather than the SA node become the pacemaker of the heart.  The pathway of the ventricular impulses is different from normal conduction, producing a  wide (>0.10 seconds), bizarre QRS complex. 36
  37. Ventricular Tachycardia  ETIOLOGY.  Myocardial irritability, MI, and cardiomyopathy are common causes of VT. Respiratory acidosis, hypokalemia, digoxin toxicity, cardiac catheters, and pacing wires can also produce VT. 37
  38. Pathophysiology of Primary Hypertension  Altered Renin-Angiotensin- Aldosterone Mechanism  High plasma renin activity (PRA) results in the increased conversion of angiotensinogen to angiotensin I.  This alteration in the RAAS may contribute to the development of hypertension. 38
  39. Pathophysiology of Primary Hypertension  Stress and Increased Sympathetic Nervous System Activity.  Physiologic responses to stress, which are normally protective, may persist to a pathologic degree, resulting in a prolonged increase in SNS activity.  Increased SNS stimulation produces increased vasoconstriction, increased HR, and increased renin release.  Increased renin activates the RAAS, leading to elevated BP.  People exposed to high levels of repeated psychologic stress develop hypertension to a greater extent than those who experience less stress. 39
  40. Insulin Resistance and Hyperinsulinemia  Insulin resistance is a risk factor in the development of hypertension and CVD.  High insulin levels stimulate SNS activity and impair nitric oxide– mediated vasodilation.  Additional pressor effects of insulin include vascular hypertrophy and increased renal sodium reabsorption.40
  41. Joint National Committee (JNC) 8 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  42. Clinical Manifestations  Hypertension is often called the “silent killer” because it is frequently asymptomatic until it becomes severe and target organ disease occurs.  secondary symptoms include fatigue, dizziness, palpitations, angina, and dyspnea. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 42
  43. Complications  Coronary Artery Disease  The mechanisms by which hypertension contributes to the development of atherosclerosis are not fully known.  The “response-to-injury” theory of atherogenesis suggests that hypertension disrupts the coronary artery endothelium. This results in a stiff arterial wall with a narrowed lumen, and accounts for a high rate of CAD, angina, and MI.  Left Ventricular Hypertrophy.  Sustained high BP increases the cardiac workload and produces left ventricular hypertrophy (LVH)  Progressive LVH, especially in the presence of CAD, is associated with the development of heart failure.  Heart Failure  Heart failure occurs when the heart’s compensatory mechanisms are overwhelmed, and the heart can no longer pump enough blood to meet the body’s demands Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  44. Complications  Cerebrovascular Disease.  Atherosclerosis is the most common cause of cerebrovascular disease.  Hypertension is a major risk factor for cerebral atherosclerosis and stroke  Peripheral Vascular Disease.  Hypertension speeds up the process of atherosclerosis in the peripheral blood vessels. This leads to the development of peripheral vascular disease, aortic aneurysm, and aortic dissection.  Intermittent claudication (ischemic leg pain precipitated by activity and relieved with rest) is a classic symptom of peripheral vascular disease. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  45. Complications  Nephrosclerosis.  Hypertension is one of the leading causes of chronic kidney disease  Renal disease results from ischemia caused by the narrowing of the renal blood vessels.  Laboratory indications of renal disease are microalbuminuria, proteinuria, microscopic hematuria, and elevated serum creatinine and blood urea nitrogen (BUN)  levels. The earliest manifestation of renal disease is usually nocturia  Retinal Damage.  Damage to the retinal vessels provides an indication of related vessel damage in the  heart, brain, and kidneys.  Manifestations of severe retinal damage include blurring of vision, retinal hemorrhage, and loss of vision. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  46. Diagnostic Studies Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 46
  47. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. Ambulatory Blood Pressure Monitoring. Some patients have elevated BP readings in a clinical setting and normal readings when BP is measured elsewhere. This phenomenon is referred to as “white coat” hypertension. Self- monitoring of BP is an easy, cost-effective approach that may be chosen before ambulatory BP monitoring (ABPM).
  48. Collaborative Care  Goals include achieving and maintaining goal BP and reducing cardiovascular risk and target organ disease.  Lifestyle modifications are indicated for all patients with prehypertension and hypertension. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 48
  49. Collaborative Care  Lifestyle Modifications.  Lifestyle modifications are directed toward reducing the patient’s BP and overall cardiovascular risk. Modifications include  (1) weight reduction  (2) Dietary Approaches to Stop Hypertension (DASH) eating plan  (3) dietary sodium reduction,  (4) moderation of alcohol consumption,  (5) regular physical activity,  (6) avoidance of tobacco use (smoking and chewing)  (7) management of psychosocial risk factors Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 49
  50. Drug Therapy Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 50 The drugs currently available for treating hypertension have two main actions: (1)they decrease the volume of circulating blood (2)they reduce SVR
  51. Site and method of action of various antihypertensive drugs Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 51
  52. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  53. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 53
  54. Nursing Management: Primary HTN. 54 • Assessment • Subjective data • Objective Data • Nursing Diagnosis • Priority Diagnosis • Collaborative problems • Planning • Overall Goals: Patient will: • (1) achieve and maintain the goal BP; (2) understand • and follow the therapeutic plan; (3) experience minimal or no unpleasant side effects of therapy; and (4) be confident of the ability to manage and cope with this condition.
  55. Nursing Management: Primary HTN. 55 • Implementation • Health Promotion • Individual Patient Evaluation • Blood Pressure Measurement • Screening Programs • Cardiovascular Risk Factor Modification
  56. GERONTOLOGIC CONSIDERATIONS  The lifetime risk of developing hypertension is approximately 90% for middle-aged (ages 55 to 65) and older (over 65) normotensive men and women  Isolated systolic hypertension (ISH) is the most common form of hypertension in people over 50 years of age.  In the older adult who is taking antihypertensive medication, absorption of some drugs may be altered as a result of decreased blood flow to the gut.  Metabolism and excretion of drugs may also be prolonged.  Some older people have a wide gap between the first Korotkoff sound and subsequent beats. This is called the auscultatory gap. Failure to inflate the cuff high enough may result in underestimating SBP Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 56
  57. GERONTOLOGIC CONSIDERATIONS  The pathophysiology of hypertension in the older adult  involves the following age-related physical changes:  (1) loss of elasticity in large arteries from atherosclerosis,  (2) increased collagen content and stiffness of the myocardium.  (3) increased peripheral vascular resistance,  (4) decreased adrenergic receptor sensitivity,  (5) blunting of baroreceptor reflexes.  (6) decreased renal function.  (7) decreased renin response to sodium and water depletion. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 57
  58. GERONTOLOGIC CONSIDERATIONS  Because of varying degrees of impaired baroreceptor reflexes, orthostatic hypotension often occurs in older adults, especially in those with ISH.  Older adults experience postprandial drops in BP.  The greatest decrease occurs approximately 1 hour after eating.  BP returns to preprandial levels 3 to 4 hours after eating.  Avoid giving vasoactive medications with meals.7 Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 58
  59. HYPERTENSIVE CRISIS 59 • is a term used to indicate either a hypertensive urgency or emergency. This is determined by the degree of target organ disease and how quickly the BP must be lowered. • BP is severely elevated (often above 220/140 mm Hg) with clinical evidence of target organ disease. • Hypertensive urgency develops over days to weeks. This is a situation in which a patient’s BP is severely elevated (usually above 180/110 mm Hg), but there is no clinical evidence of target organ disease Hypertensive urgencies usually do not require IV medications but can be managed with oral agents.
  60. HYPERTENSIVE CRISIS 60 Clinical Manifestations  A hypertensive emergency is often manifested as hypertensive encephalopathy, a syndrome in which a sudden rise in BP is associated with severe headache, nausea, vomiting, seizures, confusion, and coma.  The manifestations of encephalopathy are the result of increased cerebral capillary permeability.  This leads to cerebral edema and a disruption in cerebral function.
  61. HYPERTENSIVE CRISIS 61  In treatment of hypertensive emergencies, the mean arterial pressure (MAP) is often used instead of BP readings to guide and evaluate drug therapy. Antihypertensive drugs administered IV have a rapid (within seconds to minutes) onset of action. Assess the patient’s BP and pulse every 2 to 3 minutes during the initial administration of these drugs.
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