Adult Care Nursing I/Theory 2024-2025 Lectures 12-14 PDF

Adult Care Nursing I / Theory 2024-2025 Lectures 12-14 Unit 6, Chapter 25: Assessment of Cardiovascular Function  Objectives Describe the relationship between the anatomic structures and the physiologic function of the cardiovascular system. D...

Adult Care Nursing I / Theory 2024-2025 Lectures 12-14 Unit 6, Chapter 25: Assessment of Cardiovascular Function  Objectives Describe the relationship between the anatomic structures and the physiologic function of the cardiovascular system. Discuss the clinical indications, patient preparation, and other related nursing implications for common tests and procedures used to assess cardiovascular function and diagnose cardiovascular diseases. Anatomy of the Heart Cardiac Conduction System: Electrophysiology (60-100) (40-60) (20-40) (20-40) Pulmonary and Systemic Circulation  Cardiac Hemodynamics Stroke Volume(SV): Amount of blood ejected with each heartbeat (about 60 to 130 mL at rest). – Preload: Degree (amount) of stretch of cardiac muscle fibers at the end of diastole.(EDV) – Afterload: Resistance to ejection of blood from ventricle. Ejection Fraction: (SV/EDV), Percent % of end diastolic volume ejected with each heartbeat (measured for left ventricle, normal range 55%-65%). Cardiac Output (CO): Amount of blood pumped by ventricle in liters per minute. CO = SV × HR (L/min). (about 4 to 6 L/min at rest).  Assessment  Health history  Physical Examination Family History Heart inspection, palpation, auscultation Medications Vital Signs Nutrition Sexuality, Reproduction Elimination Coping, Stress Tolerance Activity, Exercise Prevention Strategies Sleep, Rest Risk factors Self-perception, Self- o Modifiable concept o Nonmodifiable Roles, Relationships  Diagnostic Evaluation  Laboratory Tests  Cardiac Biomarkers: Lipid Profile Creatine kinase (CK), CK Brain (B-type) natriuretic isoenzymes (CK-MB) peptide Myoglobin C-reactive protein Troponin T and I : most Homocysteine indicative of cardiac (atherosclerosis) damage Blood chemistry, hematology, coagulation & Proteins:  Electrocardiography 12-lead ECG, 15-lead ECG, and 18-lead ECG Continuous monitoring: hardwire, telemetry, lead systems & ambulatory monitoring. I. Continuous ambulatory monitoring (Holter monitor) II. Continuous Real-Time Monitors III. Cardiac Event Recorders IV. Cardiac Implantable Electronic Devices  Electrocardiography  Cardiac Stress Testing Exercise stress testing – Pt walks on treadmill with intensity progressing according to protocols – Terminated when target HR is achieved (50%-85% of MAX HR). MAX HR= 220 minus age – ECG, V/S, symptoms monitored Pharmacologic stress testing: - Vasodilating agents given to mimic exercise  Electrocardiography Echocardiography Noninvasive ultrasound test that is used to: – Measure the ejection fraction – Examine the size, shape, and motion of cardiac structures (such as valves and ventricular walls) o Transthoracic or Transesophageal  Diagnostic Tests Radionuclide Imaging Additional Imaging – Myocardial Perfusion – Computed Tomography (CT Imaging: Single Photon scan) Emission Computed Tomography (SPECT), and – Magnetic Resonance Positron Emission Angiography (MRA) Tomography (PET) – Test of ventricular function, wall motion  Cardiac Catheterization Invasive procedure used to diagnose structural & functional diseases of the heart & great vessels. Used to measure cardiac chamber pressures & assess patency of coronary arteries.  Right Heart Cath: to assess the function of the right ventricle and tricuspid and pulmonary valves o Pulmonary artery pressure and oxygen saturations may be obtained; biopsy of myocardial tissue may be obtained  Left Heart Cath:to evaluate the aortic arch & its major branches, patency of the coronary arteries, & the function of the left ventricle & mitral and aortic valves o Involves use of contrast agent  Nursing Interventions-Cardiac Cath Assessment prior to test; allergies, blood work. Patient education pre- and post-procedure. Post procedure; Observe cath site for bleeding, hematoma Assess peripheral pulses Evaluate temp, color, and cap refill of affected extremity Screen for dysrhythmias Activity restrictions; Maintain bed rest 2 to 6 hours Instruct patient to report chest pain or dyspnea Monitor for contrast-induced nephropathy Ensure patient safety Cardiac Catheterization Cardiac Catheterization Cardiac Catheterization Animation  Adult Care Nursing I / Theory 2024-2025 Unite 6; Chapter 26: Management of Patients With Dysrhythmias & Conduction Problems  Normal Electrical Conduction SA node (sinus node) (60-100) AV node (40-60) Conduction Bundle of His (20-40) (20-40) Right and left bundle branches Purkinje fibers Depolarization = Electrical Stimulation = Systole Repolarization = Electrical Relaxation = Diastole The Electrocardiogram (ECG) Interpretation  The ECG reflects ECG Interpretation electrical activity of the heart. – P wave Electrode placement – QRS complex – Electrode adhesion – T wave Types of ECG: – U wave  12, 15, or 18 lead ECG – PR interval  Hardwire monitoring – ST segment  Telemetry – QT interval  Holter monitor – TP interval – PP interval 12-lead ECG: Precordial & Limb Lead Placement Diagram  ECG Graph and Commonly Measured Components  Each small box represent 0.04 second on the horizontal axis &1 mm or 0.1 millivolt on the vertical axis.  Time & rate are measured on the horizontal axis of the graph, & amplitude or voltage is measured on the vertical axis.  When an ECG waveform moves toward the top of the paper, it is called a positive deflection. When it moves toward the bottom of the paper, it is called a negative deflection.  P wave & QRS Complex  P Wave  Represents Atrial Depolarization, electrical impulses at the SA node  Normally it is 0.11 sec by duration, and 2.5mm in height or less.  QRS Complex  Represents Ventricular Depolarization  It is less than 0.12 sec in duration  Composed of three waves: Q, R, S  When a wave is less than 5 mm in height, small letters (q, r, s) are used  QRS Complex  Q wave is the first negative deflection after P wave – It is less than.04 sec by duration  R wave is the first positive deflection after P wave  S wave is the first negative deflection after R wave  T wave – Represents Ventricular Repolarization (Resting state) – Follows the QRS complex and usually has the same direction (deflection) of QRS complex  U wave – Represents Repolarization of Purkinje Fibers – (Rare); Not always present, seen in hypokalemia, heart disease, & hypertension – U wave follows the T wave & is usually smaller than the P wave but if tall could be mistaken for an extra P wave.  PR Interval  Represents the time needed for  SA stimulation +  Atrial depolarization +  Conduction through the AV node before ventricular depolarization (end of bundle of His)  It is onset of Atrial depolarization to the onset of Ventricular depolarization  Measured from the beginning of the P wave to the beginning of the QRS complex  It is 0.12 - 0.20 sec in duration  ECG  QT Interval:  Represents the total time for ventricular depolarization & repolarization.  Is measured from the beginning of the QRS complex to the end of the T wave.  The QT interval varies with heart rate, gender, and age  The QT interval is usually 0.32 to 0.40 seconds in duration if the heart rate is 65 to 95 bpm  ECG  TP Interval: Is measured from the end of the T wave to the beginning of the next P wave—an isoelectric period When no electrical activity is detected, the line on the graph remains flat; this is called the isoelectric line. The ST segment is compared with the TP interval to detect ST segment changes.  ST Segment  Represents early Ventricular Repolarization  lasts from the end of the QRS complex to the beginning of the T wave  Is analyzed to identify whether it is isoelectric or not (ST segment is normally isoelectric)  ST segment depression: may indicate cardiac ischemia.  ST segment elevation: may indicate cardiac injury.  ECG  PP Interval:  Represents Atrial cycle (i.e., beginning of the P wave to the beginning of the next P wave  Determines Atrial rate & rhythm  RR Interval:  Used to determines Ventricular rate and rhythm  Measured from one QRS to the next QRS complex.  Determining Heart Rhythm From ECG Use P-P intervals to determine Atrial rhythm Use R-R intervals to determine Ventricular rhythm Equal intervals means regular rhythm If the intervals are different, the rhythm is called irregular. A 1-minute (60 seconds) rhythm strip contains 300 large boxes and 1,500 small boxes. Determining Heart Rhythm From ECG – 1 small box = 0.04 sec – 1 big box = 0.2 sec – 5 large boxes = 1 sec – 30 large boxes = 6 sec – 300 large boxes = 1500 small boxes = 60 second  Determining Heart Rate From ECG  Regular rhythm – 1500 divided by the number of small boxes between two R waves (Heart Rate = 1500/No of small boxes) Or – 300 divided by the number of large boxes between two R waves (HR = 300/ No of large boxes) For example, if there are 10 small boxes (2 large boxes) between two R waves, the heart rate is 1,500/10 =150 bpm; HR = 300/2= 150 bpm If there are 25 small boxes (5 large boxes) , the heart rate is 1,500/25 = 60 bpm; 300/5 = 60 bpm (see Fig. 26-4A).  Determining Heart Rate From ECG  Irregular rhythm  Count the number of RR or PP intervals in 6 seconds (30 large boxes) and multiply that number by 10.  The top of the ECG paper is usually marked at 3-second intervals, which is 15 large boxes horizontally Less accurate method  For example, if there are approximately 7 RR intervals in 6 seconds, so there are about 70 RR intervals in 60 seconds (7 × 10 = 70). The ventricular HR is 70 bpm (see Fig. 26-4B).  Heart Rate Determination Figure 26-4 A. Ventricular & atrial heart rate determination with a regular rhythm: 1,500 divided by the number of small boxes between two P waves (atrial rate) or between two R waves (ventricular rate). In this example, there are 25 small boxes between both R waves & P waves, so the heart rate (HR) is 60 bpm. B. Heart rate determination if the rhythm is irregular. There are approximately 7 RR intervals in 6 seconds, so there are about 70 RR intervals in 60 seconds (7 × 10 = 70). The ventricular HR is 70 bpm.  Dysrhythmias Disorders of formation or conduction (or both) of electrical impulses within heart. Can cause disturbances of: Rate, Rhythm, Both rate & rhythm Dysrhythmias can be life-threatening and can occur in the Atria, Ventricles, or in both. Potentially can alter blood flow & cause hemodynamic changes (change pumping action of the heart & decrease BP). Diagnosed by analysis of ECG waveform Their treatment is based on the frequency & severity of symptoms produced.  Consequences of Dysrhythmias Dysrhythmias interfere with the heart’s pumping ability Bradycardic rhythms impair blood flow to vital organs by decreasing total cardiac output (CO). Tachycardic rhythms shorten diastolic filling time which will lead to decrease stroke volume (SV) and overall cardiac output and decrease coronary artery perfusion. In addition, it will increase myocardial workload and O2 demands. Atrial dysrhythmias reduce the overall cardiac output by 20%. Ventricular dysrhythmias can dramatically reduce diastolic filling to a point where CO is severely diminished producing absence of pulse and blood pressure.  Etiology- Dysrhythmias Hypoxia Pulmonary Disorders Shock Electrolyte imbalances Poisoning Metabolic Imbalances Drug Ingestion Myocardial Infarction (MI) Congestive Heart Failure (CHF)  Manifestations of Dysrhythmias Irregular rate and rhythm, Numbness of Arms palpitation Weakness and Fatigue Chest, neck, shoulder, or arm pain Cold Skin Dizziness Nausea and Vomiting Dyspnea Decreased Blood Pressure (BP) Extreme restlessness Decreased O2 Saturation Decreased level of Consciousness  Normal Sinus Rhythm Normal sinus rhythm occurs when the electrical impulse starts at a regular rate & rhythm in the SA node & travels through the normal conduction pathway. Ventricular & Atrial rate 60-100 in an adult, & regular rhythm QRS shape & duration usually normal (less than.12 sec) P wave normal & consistent shape, always in front of QRS. PR interval consistent (0.12-0.20 seconds) P:QRS ration 1:1  Normal Sinus Rhythm (NSR) Ventricular and Atrial Rate 60 -100 b/min Ventricular and Atrial Rhythm Regular P wave Normal & consistent shape (Upright), always in front of the QRS Normal ( less than QRS shape & duration 0.12 sec) P-R interval Constant, duration : 0.12 - 0.20 sec P : QRS ratio 1:1  Types of Dysrhythmias:  Sinus Node Dysrhythmias: (originate in the SA node) Sinus Bradycardia (abnormally slow heart rates). Sinus Tachycardia (rapid heart rates). Sinus Arrhythmia  Atrial Dysrhythmias (originate in the atria) Atrial Flutter, Atrial Fibrillation (AF) & Premature atrial complexes (PACs)  Junctional Dysrhythmias (originate within AV nodal)  Ventricular Dysrhythmias (originate in the ventricle) Ventricular Tachycardia (VT), Ventricular Fibrillation (VF) Ventricular asystole (absence of rhythm formation)  Sinus Bradycardia Discharge rate (impulse) from the SA node is slower than normal rate. Rate < 60 beats/min, Regular rhythm Sinus Bradycardia Ventricular and Atrial Rate Less than < 60 b/min Ventricular and Atrial rhythm Regular QRS shape & duration Normal ( less than 0.12 sec) P wave Normal and consistent in shape, always in front of the QRS P-R interval Constant interval duration : 0.12- 0.20 second P : QRS ratio 1:1 Sinus Bradycardia  Sinus Bradycardia Causes: – Lower metabolic needs (e.g., sleep, athletic training, hypothyroidism) – Vagal stimulation (e.g., vomiting, suctioning, severe pain) – Medications (e.g., Beta blockers: metoprolol; ca+ ch. Blockers: nifedipine) – Coronary Artery Disease (CAD) (e.g., MI) – Hypoxemia – Idiopathic sinus node dysfunction – Altered mental status (Delirium) – Increased Intracranial Pressure (ICP)  Sinus Bradycardia  Medical Management: Depends on cause & symptoms Treat underlying causes If the bradycardia produces signs & symptoms of clinical instability (e.g., acute alteration in mental status, chest discomfort, or hypotension), 0.5 mg of Atropine given rapidly as (IV) bolus & repeated every 3-5 minutes until a maximum dosage of 3 mg is given. Atropine blocks vagal stimulation Rarely if No response to Atropine: emergency transcutaneous pacing & Catecholamines such as Dopamine or Epinephrine, are given. Sinus Tachycardia SA node creates an impulse faster-than-normal rate (e.g., vagal inhibition, sympathetic stimulation) HR in an adult is >100 beats/min but usually 100 b/min (usually less than 120 b/min) Ventricular & Atrial rhythm Regular QRS shape & duration Normal (less than 0.12 sec) P wave Normal and consistent in shape, always in front of the QRS may be buried in the preceding T wave P-R interval Constant interval between 0.12- 0.20 sec P : QRS ratio 1:1 Sinus Tachycardia Sinus Tachycardia  Causes: Physiologic or psychological stress (e.g., acute blood loss, anemia, shock, hypo/hypervolemia, heart failure, pain, fever, exercise, anxiety) Stimulants of the sympathetic response: – Medications (e.g., Atropine, Catecholamines) – Stimulants (e.g., Caffeine, Nicotine) – illicit drugs (e.g., amphetamines , cocaïne) Excessive sympathetic tone Autonomic dysfunction (e.g., Postural Orthostatic Tachycardia Syndrome POTS)  Sinus Tachycardia Medical Management: – Depends on cause & symptoms – Goal to reduce HR & decrease myocardial oxygen consumption – Treat underlying causes – Persistent tachycardia with hemodynamic instability- synchronized cardioversion – Vagal maneuver and Adenosine administration – Beta blockers and Calcium channel blockers  Sinus Arrhythmia SA node creates an impulse at an irregular rhythm Rate increase with inspiration and decreases with expiration.  Causes: – Heart disease and rarely valvular disease  Medical Management: Not typically treated because it does not cause any significant hemodynamic effect. Sinus Arrhythmia Ventricular and Atrial rate 60 to 100 b/min Ventricular and Atrial Irregular rhythm QRS shape & duration Normal (less than 0.12 sec) Normal and consistent in shape, P wave always in front of the QRS Constant interval between P-R interval 0.12- 0.20 sec P : QRS ratio 1:1 Sinus Arrhythmia  Atrial Dysrhythmias Atrial dysrhythmias originate from foci (somewhere else) within the atria and not the SA node. Examples – Atrial Flutter – Atrial Fibrillation (AF) – Premature atrial complexes (PACs)  Atrial Flutter  Atrial flutter is related to conduction defect in the atrium, results in a rapid (250 to 400 b/min) and regular Atrial rate.  Because atrial rate is faster than the AV node can conduct, not all atrial impulses are conducted into the ventricle, causing a therapeutic block at the AV node.  Electrical impulses take an abnormal path through the Atria (circulating) Atrial Flutter Ventricular and Atrial rate Atrial rate: 250 – 400 b/m Ventricular rate: 75 -150 b/m Ventricular and Atrial rhythm Atrial: Regular Ventricular usually Regular but may be irregular because of a change in the AV conduction. QRS Normal shape & duration P wave Saw-toothed shape or F waves P-R interval Difficult to be determined Because of the flutter waves' proximity to the QRS complex P : QRS ratio 2:1 or 3 :1 or 4 :1 Atrial Flutter 3:1 Atrial flutter 4:1 Atrial flutter Atrial Flutter Mostly associated with cardiovascular disease – Valvular disease – HTN – CAD & Cardiomyopathy – Open Heart Surgery Seen in other conditions (Hyperthyroidism, PH, COPD) Atrial flutter can cause serious signs and symptoms, such as chest pain, shortness of breath, and low blood pressure. Atrial Flutter  Medical Management: – Vagal maneuver – Adenosine IV by rapid administration, & immediately followed by a 20-mL saline flush & elevation of the arm with the IV line to promote rapid circulation of the medication. – Electrical Cardioversion: converting atrial flutter to sinus rhythm – Antithrombotic therapy Atrial Fibrillation  Uncoordinated Atrial electrical activation that causes a rapid, disorganized, and uncoordinated twitching of Atrial musculature. The most common sustained dysrhythmia. Highly linked with stroke, dementia, and premature death. Patients are at increased risk of heart failure, myocardial ischemia, & embolic events such as stroke Atrial Fibrillation  Increase risk of stroke by five folds, thus requires Anticoagulation therapy (Warfarin) as prophylaxis if Atrial fibrillation is persistent. Atrial Fibrillation Ventricular and Atrial Atrial: 300 – 600 b/m rate Ventricular: 120–200 b/m Ventricular and Atrial Highly irregular rhythm QRS shape & duration Usually normal P wave Not definite wave ; irregular waves that vary in amplitude & shape are seen & referred to as fibrillatory or f waves P-R interval Cannot be measured P : QRS ratio Many : 1  Atrial Fibrillation Causes: – The exact cause is unknown. – Open Heart Surgery / Valvular heart disease (Mitral/Tricuspid) – Inflammatory of infiltrative disease (e.g., Pericarditis, Myocarditis) – Cardiomyopathies (e.g., dilated or restrictive) – Coronary Artery Disease & Heart Failure – Hypertension, DM and Congenital disorders – Can be found with obstructive sleep apnea, PH, PE, Alcohol abuse.  Atrial Fibrillation Medical Management: – History & physical exam – 12-lead ECG, Echocardiogram, & blood tests (thyroid, hepatic, & renal functions) – Chest x-ray, Exercise test, Holter monitoring – Treatment depends on cause, pattern, and duration of the dysrhythmia. – Cardioversion with hemodynamic instability – Antithrombotic agents (e.g., Warfarin) – Other drugs (e.g., Amiodarone, Beta blockers) – Cardiac rhythm therapies, catheter ablation  Ventricular Dysrhythmias Ventricular dysrhythmias originate from foci within the ventricles Ventricular arrhythmias result from ventricular cell ischemia (as seen with acute MI), Electrolyte imbalances (hypokalemia , hypoxia) and Digitalis. HR is not measurable, P wave is not visible, PR interval and the QRS interval are not measurable.  Ventricular Tachycardia (VT)  VT is defined as three or more Premature Ventricular Complex (PVCs) in a row, occurring at a rate exceeding 100 beats/m. Causes: cardiac ischemia or infarction, increased workload on the heart (e.g., HF and tachycardia), digitalis toxicity, hypoxia, acidosis, or electrolyte imbalances, especially hypokalemia, with higher risk if associated with MI and low ejection fraction (EF). Manifestations: VT is an emergency, unresponsive, pulseless, hemodynamic loss, etc.  Ventricular Tachycardia Ventricular and Atrial Atrial: depends on rate underlying rhythm Ventricular:100-200b/m Ventricular and Atrial Regular rhythm QRS shape & duration 0.12 seconds or longer with bizarre and abnormal shape P wave Very difficult to detect P-R interval Very irregular P : QRS ratio Difficult to determine  Ventricular Tachycardia Medical Management – Depends on the rhythm, assessment of patients, obtain ECG. – Defibrillation for pulseless VT. If VT is witnessed with no defibrillator, precordial thumb may be used. – May need Antiarrhythmic medications (e.g., Amiodarone, Lidocaine) – Cardioversion for monophasic VT (consistent QRS shape and rate) – Long-term treatment- if ejection fraction is 35%, managed by Amiodarone.  Ventricular Fibrillation (VF) Is a rapid, disorganized ventricular rhythm that causes ineffective quivering of the ventricles. Most common dysrhythmia in patients with cardiac arrest. No atrial activity is seen on ECG. Causes: CAD, MI, untreated VT, cardiomyopathy, electrical shock.  Ventricular Fibrillation Ventricular rate Ventricular >300 bpm Ventricular rhythm Extremely irregular without a specific pattern QRS shape & duration Irregular, undulating waves without recognizable QRS complexes P wave Very difficult to detect P-R interval Very irregular P : QRS ratio Difficult to determine  Ventricular Fibrillation Medical Management: Characterized by absent pulse and respiration. Cardiac arrest and death imminent if not treated Immediate Defibrillation, or CPR if defibrillator is not available. 5 cycles of CPR after Defibrillation Intubation Epinephrine, Amiodarone, etc. Monitor for complications  Ventricular Asystole - Flatline Characterized by absent QRS complexes, P waves may be apparent for a short duration. There is no heartbeat, no palpable pulse, & no respiration Without immediate treatment, ventricular asystole is fatal. Ventricular asystole is treated by high-quality CPR with minimal interruptions Nursing Process: Care of the Patient with a Dysrhythmia—Assessment Causes of dysrhythmia, contributing factors Assess indicators of cardiac output and oxygenation Health history: previous occurrences of decreased cardiac output, possible causes of the dysrhythmia All medications (prescribed & over-the-counter OTC) Psychosocial assessment: patient’s “perception” of dysrhythmia  Assessment Physical assessment include: – Skin (pale and cool) – Signs of fluid retention (jugular veins distended, lung auscultation) – Signs of decreased CO (altered loss of consciousness) – Rate, rhythm of apical, peripheral pulses – Heart sounds – Blood pressure, pulse pressure  Nursing Diagnoses Decreased cardiac output related to inadequate ventricular filling or altered heart rate Anxiety related to fear of the unknown outcome of altered health state Deficient knowledge about the dysrhythmia and its treatment Collaborative Problems and Potential Complications Cardiac arrest Heart Failure (HF) Thromboembolic event, especially with Atrial fibrillation (AF).  Nursing Interventions Monitor and manage the Dysrhythmia Reduce Anxiety Promote home- and community-based care Educate the patient about self-care Continuing care  Nursing Intervention: Monitor and Manage the Dysrhythmia Assess vital signs on an ongoing basis Assess for lightheadedness, dizziness, fainting  If hospitalized: – Obtain 12-lead ECG – Continuous monitoring – Monitor rhythm strips periodically Antiarrhythmic medications – “6-minute walk test” which is used to identify the patient’s ventricular rate in response to exercise Nursing Intervention: Minimize Anxiety Stay with patient Maintain safety and security Discuss emotional response to Dysrhythmia Help patient develop a system to identify factors that contribute to episodes of the Dysrhythmia Maximize the patient’s control Nursing Intervention: Promote Home and Community-Based Cared Educate the patient – Treatment options – Therapeutic medication levels – How to take pulse before medication administration – How to recognize symptoms of the Dysrhythmia – Measures to decrease recurrence – Plan of action in case of an emergency – CPR (Family)  Adjunctive Modalities and Management  Used when medications alone are ineffective against dysrhythmia Pacemakers / for bradycardias Cardioversion / for acute tachydysrhythmia Defibrillation / for acute tachydysrhythmia  The device name called a defibrillator  The electrical voltage required to defibrillate the heart is usually greater than that required for cardioversion.  Nurse responsible for assessment of the patient’s understanding regarding the mechanical therapy Adjunctive Modalities and Management The amount of voltage used varies from 50 to 360 joules, depending on the type & duration of the dysrhythmia, and hemodynamic status of patient  Cardioversion and Defibrillation Treat tachydysrhythmias by delivering electrical current that depolarizes critical mass of myocardial cells. – When the cells repolarize, SA node usually able to recapture role as the heart pacemaker The difference between cardioversion & defibrillation is the timing of the delivery of electrical current In cardioversion, the delivery of electrical current is synchronized with patient’s electrical events; ECG  Electrical impulse discharges during ventricular depolarization (QRS complex) In defibrillation, the delivery of current is immediate and unsynchronized. Used in emergency for VF, pulseless VT, & unconscious patients.  Safety Measures Ensure good contact between skin, pads, and paddles – Use conductive medium, 20 to 25 pounds of pressure Place paddles so they do not touch bedding or clothing and are not near medication patches or oxygen flow If cardioverting, turn synchronizer on If defibrillating, turn synchronizer off Do not charge device until ready to shock Call “clear” three times; follow checks required for clear – Ensure no one is in contact with patient, bed, or equipment