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Transcript
1 Atrial Dysrhythmias John Miller The Cardiac Cycle and Cardiac Output Systole and diastole Cardiac output (CO) = HR × SV Factors influencing CO o Activity level o Metabolic rate o Physiologic and psychologic stress responses o Age o Body size Heartrate, Contractility, and Preload Heart rate o Direct stimulation by sympathetic, parasympathetic nerves Contractility o Ability of cardiac muscle fibers to shorten Preload o Amount of cardiac muscle fiber tension at the end of diastole Afterload and Indicators of Cardiac Output Afterload o Force the ventricles must overcome to eject their blood volume o Pressure in the arterial system ahead of the ventricles Clinical indicators of CO o Cardiac index (CI) Adjusted for patient's body surface area (BSA) The Conduction System of the Heart Intrinsic conduction o Complex electrical circuit that perpetuates cardiac cycle Sinoatrial (SA) node Atrioventricular (AV) node Cardiac rate and rhythm assessment Tachycardia or bradycardia Dysrhythmia Sinus node o Decrease in number of pacemaker cells The Patient with a Cardiac Dysrhythmia Disturbance or irregularity in the electrical system of the heart Reasons for development o Not all pathologic o Exercise o Fear 2 Properties that allow effective heart function Automaticity o Altered rates caused by various pacemaker cells. o Example: sinus bradycardia Excitability Conductivity o Speed at which impulse travels through the SA, AV node and Purkinje fibers. o Example: AV heart block Reentry of impulses o Reactivated muscle for a second time by the same impulse. o Example: atrial fibrillation Contractility Cardiac conduction system SA node AV node o Atrial kick Extra bolus of blood to ventricles before they contract Pathophysiology Categories of dysrhythmias o Tachydysrhythmias o Bradydysrhythmias o Ectopic rhythms Ectopic beats Heart block Reentry phenomenon o Functional reentry Risk factors Myocardial ischemia: angina and MI Hypoxia Vagal stimulation (autonomic nervous system) Lactic acidosis Electrolyte imbalances Drug toxicity Shock Sources of Cardiac Impulses Supraventricular rhythms Ventricular rhythms AV conduction blocks Assessment Reduced cardiac output o Palpitation, dizziness, syncope, pallor, diaphoresis, altered mental status, hypotension / shock, edema, oliguria, SOB, chest pain, fatigue, seizures o Heart rate below 50 or above 140, very irregular heart rate, or rate that does not change with exercise. 3 Electrocardiogram Assessment EKG (ECG) Lead Patterns o Electricity travels from the negative electrode to the positive one. o Lead II Right arm or shoulder lead is negative. Left leg or abdomen/lower chest is positive. Third lead is a ground. Follows the same direction as an impulse traveling from SA node to ventricles. o MCL1 is a modification of a 12 lead’s V1 lead. o Twelve lead EKG Twelve different pictures with four extremity leads and five chest leads. 12 Lead ECG The basics of the ECG in 5 min https://youtu.be/HDyqXNHLjug Cardiac Conduction System and Understanding ECG, Animation. https://youtu.be/RYZ4daFwMa8 ECG Waves P wave o First upright wave, close to atrial contraction QRS wave o 3 waves or less o Q is first downward wave, R is second upright wave, and S is second downward wave. o Close to ventricular contraction. P-R interval o Space between beginning of P-wave and the beginning of the Q wave (if Q absent, then the R wave) o Impulse traveling from the SA node into the AV node. ST segment, T wave o Ventricular repolarization QT Interval ECG Waves EKG analysis basic steps Calculate heart rate, which should be between 60-100. Measure regularity of R waves (R to R interval) and P waves (P to P interval). Examine P waves for their preceding each QRS (R wave) and their sameness. Measure the P-R interval, which should be between 0.12-0.20 seconds. Measure the duration (or width) of the QRS, which should be less than 0.12 seconds. Examine the ST segment, which should be neither elevated or depressed. Examine the T wave, which should be upright and 1/3 the height of the QRS. Examine the QT interval. Calculate heart rate Count the number of small squares between two R-waves and divide it into 1500. This method is more accurate than others. EKG paper EKG paper has small boxes on it. As it comes out of the machine, the horizontal axis of the boxes measures time in seconds. Each small box represents 0.04 seconds. 4 Supraventricular rhythms Normal sinus rhythm Sinus node dysrhythmias o Sinus arrhythmia o Sinus tachycardia o Sinus bradycardia o Sick sinus syndrome Supraventricular dysrhythmias o Premature atrial contractions (PAC) o Paroxysmal supraventricular tachycardia (PSVT) o Atrial flutter o Atrial fibrillation Increases risk for formation of thromboembolism ECG Paper Boxes Normal Sinus Rhythm (NSR or SR) Rhythm o Regular P-P and R-R intervals, varying only up to 3 mm (less than 3 small boxes). Rate o 60-100 beats / minute P waves (atrial contraction) o One precedes each QRS (ventricular contraction) P-R interval: 0.12-0.20 seconds QRS complex: less than 0.12 seconds QT interval: less than 0.40 seconds The ECG Course - Sinus Rhythms https://youtu.be/vK0XgMIYAqs Normal Sinus Rhythm Dysrhythmia Management Control the dysrhythmia rate. Remove the dysrhythmia. Reduce potential complications. Sinus Bradycardia Assessment Etiology/risk factors o Vagal stimulation (including Valsalva), drugs, MI, hyperkalemia, athletes Clinical manifestations o ECG: NSR except for HR < 60 o Symptoms of low cardiac output Assess for reduced cardiac output. Sinus Bradycardia Sinus Bradycardia Treatment If symptomatic: o Treat cause o First line of drugs: Atropine o Second line of drugs: Epinephrine or dopamine o Temporary pacemaker (transcutaneous) Stop digoxin, beta blockers (i.e. metoprolol, etc.), and calcium channel blockers (i.e. diltiazem, verapamil, nifedipine, etc. 5 Epinephrine http://www.mediccast.com/blog/wp-content/uploads/2014/12/epi-1-10000.jpg Atropine, http://www.pharmedium.com/uploads/cms/images/Atropine_Front.jpg/imagefull;max$900,900.ImageHandler External Cardiac Pacing https://youtu.be/rePqJpt7RoQ Sinus Tachycardia Assessment Etiology/risk factors o Heart failure, fluid loss, shock, respiratory distress, drugs, exercise, stress, pain Clinical manifestations o ECG: NSR except for HR > 100 Assess for reduced cardiac output. Sinus Tachycardia Sinus Tachycardia Treatment Treat cause, O2 Beta Blockers or Calcium Channel Blockers IV fluids Reduce stimulants. Paroxysmal Supraventricular Tachycardia Assessment Also known as SVT, PSVT, PAT Etiology and risk factors o CAD, MI, cardiomyopathy, extreme emotions, caffeine, cor pulmonale, digitalis toxicity, hypokalemia. Clinical manifestations o Assess for reduced cardiac output. Palpitations, dizziness Supraventricular tachycardia (SVT) https://youtu.be/eCrQDI1OAeU Paroxysmal Supraventricular Tachycardia Paroxysmal Supraventricular Tachycardia Treatment Carotid sinus massage (vagal stimulation) Beta or calcium channel blockers, digoxin, amiodarone, propafenone Cardioversion Ablation Premature Atrial Contraction (PAC) Assessment Etiology/risk factors o Ectopic foci o Valve problems, CHF (atrial enlargement) o Stress, CAD, medications, pulmonary problems o Palpitation ECG o PAC: P wave is early, differ from the other P waves, and an early QRS follows the early P. May be early sign of atrial fibrillation or flutter. o Stretching of atrial causes ectopic beats. o Assess for CHF. 6 Premature Atrial Contractions Premature Atrial Contraction (PAC) Treatment Treat cause, O2 Digoxin, metoprolol, verapamil Atrial Flutter Assessment Etiology/risk factors o Ectopic foci or rapid reentry, with atrial contraction up to 350 times per minute o CAD, mitral valve disease, PE, cardiac surgery Clinical manifestations o ECG: inverted or bidirectional, saw-toothed P-waves, with possibly a constant P-wave to QRS ratio such as 2:1 or 3:1 from AV blocking. Assess for low cardiac output. Atrial flutter (AFL) https://youtu.be/0URl8p39wQo Atrial Flutter Atrial Flutter Treatment Cardioversion (similar to defibrillation) or Drugs: o Convert to NSR: procainamide, flecainide, propafenone, dofetilide, ibutilide o Slow ventricular response: verapamil, diltiazem, amiodarone, adenosine Emergency Cardioversion https://youtu.be/xCtQ-ESsvqM Atrial Fibrillation Assessment Etiology/risk factors o Rapid chaotic atrial depolarization, up to 700 times per minute. o No atrial contraction: loss of atrial kick (decreasing cardiac output 20-30%), thrombi formation in atria o AV node blocking of some impulses o Apical-radial pulse deficit o Hypoxia, CHF Clinical manifestations o ECG: erratic baseline without P-waves, very irregular R to R intervals o Assess for low cardiac output. Atrial Fibrillation Anatomy, ECG and Stroke, Animation. https://youtu.be/tPqs4xKPG3A Atrial Fibrillation Atrial Fibrillation Treatment Thrombi and embolism prevention o Parenteral anticoagulation: Heparin (unfractionated or LMWH) o Oral anticoagulation Warfarin Direct thrombin inhibitors Dabigatran, rivaroxaban, apixaban Reduce ventricular rate 7 o Digoxin, beta or calcium channel blockers Stop dysrhythmia o Chemical cardioversion Class I drugs: Flecainide, dofetilide, propafenone, ibutilide Class IIa drugs: Amiodarone o Electrical cardioversion MAZE surgery, ablation New Anticoagulants for Stroke Prevention in Atrial Fibrillation https://youtu.be/p-gNmqiTCEw MAZE Procedure. The most effective and reliable treatment of Atrial Fibrillation (AF) https://youtu.be/UA2-B3o_sAA Catheter Ablation For Atrial Fibrillation (AFIB) https://youtu.be/SZ_uIfj-hIQ Treatment Goals for Dysrhythmias Generally Major goals of care o Identify the dysrhythmia o Evaluate its effect on physical and psychosocial well-being o Treat the underlying cause Diagnosis for Dysrhythmias Generally o Serum electrolytes o Drug levels o Arterial blood gases o Electrocardiogram o Cardiac monitoring Continuous cardiac monitoring Telemetry Home monitoring o Electrophysiology studies Nursing Care Diagnoses, outcomes, and interventions o Decreased Cardiac Output Continuity of care o Coping strategies o Lifestyle changes o Discuss fears related to treatment, implanted devices Diagnoses, outcomes, and interventions o Ineffective Tissue Perfusion: Cerebral o Impaired Spontaneous Ventilation o Spiritual Distress o Disturbed Thought Processes o Fear Risk for future episode of near SCD Community training in CPR ECG Apps for phones and tablets Play Store: https://play.google.com/store/search?q=ecg%20simulator&hl=en ITunes The 6 Second ECG Simulator http://www.skillstat.com/tools/ecg-simulator ECG Simulator Practical Clinical Skills.com http://www.practicalclinicalskills.com/ecg-simulator.aspx