Unit 4: Electrocardiography (ECG) Basic Interpretation PDF

UNIT 4: ELECTROCARDIOGRAPHY (ECG) BASIC INTERPRETATION Learning outcomes: 1. Relate concepts in cardiac anatomy and physiology 2. Apply techno-intelligent care systems and processes in the care of patients 3. Perform and interpret ECG accurately 4. Communicate effectively using cultur...

UNIT 4: ELECTROCARDIOGRAPHY (ECG) BASIC INTERPRETATION Learning outcomes: 1. Relate concepts in cardiac anatomy and physiology 2. Apply techno-intelligent care systems and processes in the care of patients 3. Perform and interpret ECG accurately 4. Communicate effectively using culturally appropriate language 5. Demonstrate caring as the core of nursing, love of God, love of country and love of people 6. Formulate a documentation regarding client’s response to the procedure 7. Generate an assessment using case scenario 8. Formulate appropriate nursing diagnoses from the given case 9. Construct a plan of care using available data from the case 10. Implement safe and quality interventions of a given simulated client’s case. 11. Evaluates the expected outcomes of simulated plan of care 12. Devise and implement health education plan to meet identified client’s learning needs. 13. Adhere to ethico-legal standards when providing safe, quality and professional nursing care in multiple contexts. 14. Collaborate with other members of the health team in the implementation of services Why do we need to learn how to interpret ECG? ECG is the most used diagnostic test for evaluating cardiac status. It graphically records the electrical currents (electrical potential) generated by the heart as waveforms that depicts depolarization (contraction) and repolarization (relaxation). This current radiates from the heart in all directions, and on reaching the skin, is measured by electrodes connected to an amplifier and strip chart recorder. It is used to diagnose and monitor certain disorders, such as myocardial infarction and pericarditis. It also allows identification of rhythm disturbances, conduction abnormalities, and electrolyte imbalances. Image source: https://speciality.medicaldialogues.in/new-drug-treatment-heart-attack-prevention- heart-failure/ Cardiovascular disease is the top cause of mortality accounting for 30% of all deaths recorded in 2010, and this figure is expected to increase in the future (WHO. 2011). CARDIAC ARREST, or Myocardial infarction (MI) or heart attack in layman’s term is one of the most fatal among cardiovascular diseases, and knowing how to interpret your patient’s ECG will prevent progression, if not, prompt earlier intervention which will prevent further damage to the heart muscles. All nurses, therefore, especially working in ER and ICU must be able to know how to read or can interpret basic ECG. Image source: https://speciality.medicaldialogues.in/new-drug-treatment-heart-attack- prevention-heart-failure/ The heart’s valves Tricuspid - AV valve between the right atrium and right ventricle Mitral - AV valve between the left atrium and left ventricle Aortic - semilunar valve between the left ventricle and the aorta Pulmonic - semilunar valve between the right ventricle and the pulmonary artery Blood flow Deoxygenated blood from the body returns to the right atrium and then flows to the right ventricle. The right ventricle pumps blood into the lungs where it’s oxygenated. Then the blood returns to the left atrium and flows to the left ventricle. Oxygenated blood is pumped to the aorta and the body by the left ventricle Coronary arteries and veins Right coronary artery - supplies blood to the right atrium and ventricle and part of the left ventricle Left anterior descending artery - supplies blood to the anterior wall of the left ventricle, interventricular septum, right bundle branch, and left anterior fasciculus of the left bundle branch Circumflex artery - supplies blood to the lateral walls of the left ventricle, left atrium, and left posterior fasciculus of the left bundle branch Cardiac veins - collect blood from the capillaries of the myocardium Coronary sinus - returns blood to the right atrium Cardiac cycle dynamics Atrial kick - atrial contraction, contributing about 30% of the cardiac output Cardiac output - the amount of blood the heart pumps in 1 minute, calculated by multiplying heart rate times stroke volume Stroke volume - the amount of blood ejected with each ventricular contraction (it’s affected by preload, afterload, and contractility) Preload - the passive stretching exerted by blood on the ventricular muscle at the end of diastole Afterload - the amount of pressure the left ventricle must work against to pump blood into the aorta Contractility - the ability of the heart muscle cells to contract after depolarization Innervation of the heart Two branches of the autonomic nervous system supply the heart: Sympathetic nervous system - increases heart rate, automaticity, AV conduction, and contractility through release of norepinephrine and epinephrine Parasympathetic nervous system - vagus nerve stimulation reduces heart rate and AV conduction through release of acetylcholine. Transmission of electrical impulses Generation and transmission of electrical impulses depend on these cell characteristics: Automaticity - a cell’s ability to spontaneously initiate an impulse, such as found in pacemaker cells Excitability - how well a cell responds to an electrical stimulus Conductivity - the ability of a cell to transmit an electrical impulse to another cardiac cell Contractility - how well the cell contracts after receiving a stimulus Depolarization-repolarization cycle Cardiac cells undergo the following cycles of depolarization and repolarization as impulses are transmitted: Phase 0: Rapid depolarization - the cell receives an impulse from a nearby cell and is depolarized Phase 1: Early repolarization - early rapid repolarization occurs Phase 2: Plateau phase - a period of slow repolarization occurs Phase 3: Rapid repolarization - the cell returns to its original state Phase 4: Resting phase - the cell rests and readies itself for another stimulus. Cardiac conduction The electrical impulse begins in the SA node and travels through the internodal tracts and Bachmann’s bundle to the AV node. From the AV node, the impulse travels down the bundle of His, along the bundle branches, and through the Purkinje fibers. Intrinsic firing rates SA node - 60 to 100/minute AV junction - 40 to 60/minute Purkinje fibers - 20 to 40/minute 1. SA node: It is the heart’s main pacemaker (generator of sinus rhythm) 2. Internodal pathways: main function is to transmit the pacing impulse from the SA node to the AV node 3. AV node: It delays impulse from atria to the ventricles ensuring that the atria have ejected their blood into the ventricles before the ventricles contract 4. Bundle of HIS: Transmits the electrical impulses from the AV node to the point of the apex of the fascicular branches 5. Left bundle branch: Transmit signal from the bundle of HIS to the left anterior fascicle and left posterior fascicle that will innervate the left ventricle 6. Left anterior fascicle: Conveys signal from the left bundle branch to the purkinje cells that will innervate the posterior and inferior aspect of the left ventricle 7. Left posterior fascicle: Conveys signal from the left bundle branch to the purkinje cells that will innervate the posterior and inferior aspect of the left ventricle 8. Right bundle branch: Transmit signal for the bundle of HIS to the purkinje fibers that will innervate the left ventricles 9. Purkinje fibers: They directly innervate the myocardial muscles and initiate the ventricular depolarization and enables the heart to contract in a coordinated fashion.