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ECGs

ECGs. Arrhythmias. Abnormal cardiac rhythms Prompt assessment of abnormal cardiac rhythm and patient’s response is critical. Phases of Cardiac Action Potential. Fig. 35-1. 12-Lead ECG. Fig. 35-3. Assessment of Cardiac Rhythm. Fig. 35-5. Assessment of Cardiac Rhythm. Fig. 35-6.

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ECGs

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  1. ECGs

  2. Arrhythmias • Abnormal cardiac rhythms • Prompt assessment of abnormal cardiac rhythm and patient’s response is critical

  3. Phases of Cardiac Action Potential Fig. 35-1

  4. 12-Lead ECG Fig. 35-3

  5. Assessment of Cardiac Rhythm Fig. 35-5

  6. Assessment of Cardiac Rhythm Fig. 35-6

  7. Assessment of Cardiac Rhythm Fig. 35-9

  8. Sinus Bradycardia • Sinus node discharges at a rate < 60 bpm • Normal rhythm in aerobically trained athletes and during sleep

  9. Sinus Bradycardia Fig. 35-11, A

  10. Sinus Bradycardia Clinical Association • Occurs in response to • Carotid sinus massage • Hypothermia • Increased vagal tone • Administration of parasympathomimetic drugs

  11. Sinus Bradycardia Clinical Association • Occurs in disease states • Hypothyroidism • Increased intracranial pressure • Obstructive jaundice • Inferior wall MI

  12. Sinus Bradycardia Significance • Hypotension with decreased CO may occur • An acute MI may predispose the heart to escape arrhythmias and premature beats

  13. Sinus Bradycardia Treatment • Consists of atropine • Pacemaker may be required

  14. Sinus Tachycardia • Discharge rate from the sinus node is increased as a result of vagal inhibition and is > 100 bpm

  15. Sinus Tachycardia Fig. 35-11, B

  16. Sinus Tachycardia Clinical Associations • Associated with physiologic stressors • Exercise • Hypotension • Hypovolemia • Myocardial ischemia • CHF

  17. Sinus Tachycardia Significance • Patients may have symptoms of dizziness and hypotension may occur • Increased myocardial oxygen consumption is associated with increased HR

  18. Sinus Tachycardia Significance • Angina or increase in infarct size may accompany persistent tachycardia in patient with acute MI

  19. Sinus Tachycardia Treatment • Determined by underlying causes • -adrenergic blockers to reduce HR and myocardial oxygen consumption

  20. Atrial Flutter • Atrial tachyarrhythmia identified by recurring, regular, sawtooth-shaped flutter waves • Associated with slower ventricular response

  21. Atrial Flutter Fig. 35-14, A

  22. Atrial Flutter Clinical Associations Usually occurs with: • CAD • Mitral valve disorders • Pulmonary embolus • Chronic lung disease • Cardiomyopathy

  23. Atrial Flutter Significance • High ventricular rates with atrial flutter can decrease CO and cause serious consequences such as heart failure • Risk for stroke because of risk of thrombus formation in the atria • Coumadin used for atrial flutter > 48h

  24. Atrial Flutter Treatment • Primary goal is to slow ventricular response by increasing AV block • Electrical cardioversion may be used to convert atrial flutter to sinus rhythm in emergency situation

  25. Atrial Flutter Treatment • Diltiazem, digoxin, and -adrenergic blockers used to control ventricular rate • Antiarrhythmic drugs used to convert atrial flutter to sinus rhythm or maintain sinus rhythm • Radiofrequency catheter ablation used as curative therapy

  26. Atrial Fibrillation • Total disorganization of atrial activity without effective atrial contraction • Chronic or intermittent

  27. Atrial Fibrillation Fig. 35-14, B

  28. Atrial Fibrillation Clinical Associations • Usually occurs with • Underlying heart disease, such as rheumatic heart disease • Cardiomyopathy • CHF • Pericarditis

  29. Atrial Fibrillation Clinical Associations • Often acutely caused by • Thyrotoxicosis • Alcohol intoxication • Caffeine use • Electrolyte disturbance • Cardiac surgery

  30. Atrial Fibrillation Significance • Can often result in decrease in CO because of ineffective atrial contractions and rapid ventricular response

  31. Atrial Fibrillation Significance • Thrombi may form in atria and may pass to brain, causing stroke • Risk for stroke increases five-fold in atrial fibrillation • Risk even higher in structural heart disease, HTN, and an age over 65

  32. Atrial Fibrillation Significance • Anticoagulation with Coumadin used to prevent stroke

  33. Atrial Fibrillation Treatment • Goals are decreased in ventricular response and conversion to sinus rhythm • Drugs for rate control include digoxin, - adrenergic blockers, and calcium channel blockers

  34. Atrial Fibrillation Treatment • Antiarrhythmic drugs used for conversion • DC cardioversion may be used to convert atrial fibrillation to normal sinus rhythm

  35. Atrial Fibrillation Treatment • Anticoagulant therapy recommended for 3 to 4 weeks in atrial fibrillation > 48 h before attempt at conversion to sinus rhythm

  36. First-Degree AV Block • Every impulse is conducted to the ventricles, but duration of AV conduction is prolonged

  37. First-Degree AV Block Fig. 35-16, A

  38. First-Degree AV Block Clinical Associations Usually occurs with: • Chronic ischemic heart disease • MI • Rheumatic fever • Vagal stimulation • Drugs such as digitalis, -adrenergic blockers, flecainide, and IV verapamil

  39. First-Degree AV Block Significance • May be a precursor to higher degrees of AV block • No treatment

  40. Second-Degree AV Block, Type 1 • Includes gradual lengthening of the PR interval, which occurs because of prolonged AV conduction time • Most commonly occurs at AV node, but can occur in His-Purkinje system

  41. Second-Degree AV Block, Type 1 Fig. 35-16, B

  42. Second-Degree AV Block, Type 1 Clinical Associations • May result from drugs such as digoxin or -adrenergic blockers • Associated with ischemic cardiac disease and other diseases slowing AV conduction

  43. Second-Degree AV Block, Type 1 Significance • Usually a result of myocardial ischemia on an inferior MI • May be warning signal of impending significant AV conduction disturbance

  44. Second-Degree AV Block, Type 1 Treatment • If symptomatic, atopine is used to increase HR or pacemaker may be needed • If asymptomatic, rhythm closely observed with transcutaneous pacemaker on standby

  45. Second-Degree AV Block, Type 2 • P wave not conducted without progressive antecedent PR lengthening • Almost always occurs when bundle branch block is present • Certain number of impulses from the sinus node are not conducted to the ventricles

  46. Second-Degree AV Block, Type 2 Fig. 35-16, C

  47. Second-Degree AV Block, Type 2 Clinical Associations • Associated with rheumatic heart disease, CAD, acute anterior MI, and digitalis toxicity

  48. Second-Degree AV Block, Type 2 Significance • Often progresses to third-degree and is associated with poor prognosis • May result in decreased CO with subsequent hypotension and myocardial ischemia

  49. Second-Degree AV Block, Type 2 Treatment • Before the insertion of a permanent pacemaker may involve use of temporary transvenous or transcutaneous pacemaker • Temporary drug measures to increase HR until pacemaker is available

  50. Third-Degree AV Heart Block • Complete heart block • Constitutes one-fourth of AV dissociation in which no impulses from atria are conducted to ventricles

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