Atrial Fibrillation

Epidemiology and Etiology

Epidemiology

• Most common form of cardiac arrhythmia
• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency increases with age
• 70% of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with atrial fibrillation (AF) are > 65 years old
• More common in men (but if affected, women are more likely to be symptomatic and develop complications)
• More common in Caucasians than African Americans, Hispanics, and Asians

General risk factors for cardiovascular disease

• Advanced age
• Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
• Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus
• Smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases
• Obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity
• Sleep apnea Sleep apnea Repeated cessation of breathing for > 10 seconds during sleep and results in sleep interruption, fatigue, and daytime sleepiness. Obstructive Sleep Apnea

Risk factors for AF

• Usually associated with some underlying heart disease
• Most common chronic disease associations are hypertensive heart disease and coronary heart disease Coronary heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease
• 15%–30% of cases are idiopathic Idiopathic Dermatomyositis or not associated with any known risk factor

Pathophysiology and Classification

Pathophysiology

• AF is caused by re-entrant electric conduction.
• Re-entrant pathways can be due to:
  • Fibrosed tissue
  • Atrial dilation (e.g., congenital Congenital Chorioretinitis defect, post-MI, valvular disease, hypertensive heart disease)
  • Abnormal accessory pathways (e.g., WPW syndrome)
• Most common site of the rapid atrial firing that triggers AF is the pulmonary veins Pulmonary veins The veins that return the oxygenated blood from the lungs to the left atrium of the heart. Lungs: Anatomy.

• Heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology: 
  • Atrial rate > 300/min
  • Some beats are irregularly modulated by the atrioventricular (AV) node
  • Ventricular rate = 90–170/min
• Effects: 
  • Atrial remodeling: irregular impulses and contractions lead to progressive dilation and fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans of the atria → higher risk for AF → vicious cycle of pathology 
  • Asynchronous contractility → atria lose systolic function 
  • Rapid uncontrolled atrial contractions ( > 300/min) → slower pass through the AV node → uncoordinated ventricular contractions (90–170/min) → tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children
  • Decreased cardiac output Cardiac output The volume of blood passing through the heart per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with stroke volume (volume per beat). Cardiac Mechanics → stasis of blood →  promotes thromboembolism Thromboembolism Obstruction of a blood vessel (embolism) by a blood clot (thrombus) in the blood stream. Systemic Lupus Erythematosus 
  • Decreased cardiac output Cardiac output The volume of blood passing through the heart per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with stroke volume (volume per beat). Cardiac Mechanics → heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR)

Classification

• Paroxysmal: AF that starts spontaneously and terminates spontaneously or with intervention within 7 days of onset; episodes may occur with variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables frequency
• Persistent: AF that fails to self-terminate within 7 days, requires pharmacologic or electrical cardioversion to terminate
• Long-standing persistent: AF that has lasted for more than 12 months
• Permanent: AF that is unresponsive to treatment, patient and doctor decide to no longer pursue a rhythm control strategy
• Lone: paroxysmal, persistent, or permanent AF with no structural heart disease, typically in persons < 60 years old, the lowest risk of complications → patients have a CHA₂DS₂-VASc score of “0”
• Secondary: due to underlying condition, treatment focuses on the underlying condition to resolve AF
• Subclinical: AF in asymptomatic individuals without a prior diagnosis of AF, often found in the context of implantable cardiac monitoring devices

Clinical Presentation

• AF is often asymptomatic.
• If patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship experience symptoms, these are often nonspecific and variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables.
  • Palpitations Palpitations Ebstein’s Anomaly
  • Tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children
  • Chest pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
  • Fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia
  • Dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea
  • Syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope
  • Confusion
  • Mild dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea
  • Embolic event
• If symptoms are atypical → notice signs of the underlying disorder (e.g., exophthalmos in hyperthyroidism Hyperthyroidism Hypersecretion of thyroid hormones from the thyroid gland. Elevated levels of thyroid hormones increase basal metabolic rate. Thyrotoxicosis and Hyperthyroidism, murmur in the case of a valvular defect)
• Complications of long-standing AF:
  • Signs of heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR) ( pulmonary edema Pulmonary edema Pulmonary edema is a condition caused by excess fluid within the lung parenchyma and alveoli as a consequence of a disease process. Based on etiology, pulmonary edema is classified as cardiogenic or noncardiogenic. Patients may present with progressive dyspnea, orthopnea, cough, or respiratory failure. Pulmonary Edema, orthopnea Orthopnea Pulmonary Edema, paroxysmal nocturnal dyspnea Paroxysmal nocturnal dyspnea A disorder characterized by sudden attacks of respiratory distress in at rest patients with heart failure and pulmonary edema. It usually occurs at night after several hours of sleep in a reclining position. Patients awaken with a feeling of suffocation, coughing, a cold sweat, and tachycardia. When there is significant wheezing, it is called cardiac asthma. Pulmonary Edema, dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea at rest, pitting edema Pitting edema Edema caused by excess fluid without excess colloid. Leaves “pits” due to fluid displacement when pressure is applied to the area Edema, S3 S3 Heart Sounds, S4 S4 Heart Sounds)
  • Signs of embolization Embolization A method of hemostasis utilizing various agents such as gelfoam, silastic, metal, glass, or plastic pellets, autologous clot, fat, and muscle as emboli. It has been used in the treatment of spinal cord and intracranial arteriovenous malformations, renal arteriovenous fistulas, gastrointestinal bleeding, epistaxis, hypersplenism, certain highly vascular tumors, traumatic rupture of blood vessels, and control of operative hemorrhage. Gastrointestinal Bleeding (stroke/ transient ischemic attack Transient ischemic attack Transient ischemic attack (TIA) is a temporary episode of neurologic dysfunction caused by ischemia without infarction that resolves completely when blood supply is restored. Transient ischemic attack is a neurologic emergency that warrants urgent medical attention. Transient Ischemic Attack (TIA) [ TIA TIA Transient ischemic attack (TIA) is a temporary episode of neurologic dysfunction caused by ischemia without infarction that resolves completely when blood supply is restored. Transient ischemic attack is a neurologic emergency that warrants urgent medical attention. Transient Ischemic Attack (TIA)] presenting with focal neurologic deficits Neurologic Deficits High-Risk Headaches such as paresis Paresis A general term referring to a mild to moderate degree of muscular weakness, occasionally used as a synonym for paralysis (severe or complete loss of motor function). In the older literature, paresis often referred specifically to paretic neurosyphilis. ‘general paresis’ and ‘general paralysis’ may still carry that connotation. Bilateral lower extremity paresis is referred to as paraparesis. Spinal Disk Herniation, vision Vision Ophthalmic Exam loss, or renal, splenic, or intestinal infarct Infarct Area of necrotic cells in an organ, arising mainly from hypoxia and ischemia Ischemic Cell Damage)

Diagnosis

Electrocardiogram Electrocardiogram An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) ( ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG)): confirms diagnosis

• Irregularly irregular (pathognomonic)
• RR RR Relative risk (RR) is the risk of a disease or condition occurring in a group or population with a particular exposure relative to a control (unexposed) group. Measures of Risk intervals follow no repetitive pattern
• No distinct P waves
• Narrow QRS complexes (< 0.12 seconds)

Echocardiogram Echocardiogram Transposition of the Great Vessels: used to identify etiology and complications, not for diagnosis

• Transthoracic echocardiogram Transthoracic echocardiogram Endocarditis ( TTE TTE Imaging of the Heart and Great Vessels):
  • Used to assess cardiac function
  • Rules out or confirms structural cardiac disease (e.g., valve stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS))
• Transesophageal echocardiogram Echocardiogram Transposition of the Great Vessels ( TEE TEE Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues using a transducer placed in the esophagus. Imaging of the Heart and Great Vessels):
  • Rules out or confirms the structural cardiac disease
  • Indicated if AF lasted for > 48 hrs HRS Hepatorenal syndrome (HRS) is a potentially reversible cause of acute kidney injury that develops secondary to liver disease. The main cause of hrs is hypovolemia, often as a result of forced diuresis or drainage of ascites. This leads to renal vasoconstriction resulting in hypoperfusion of the kidneys. Hepatorenal Syndrome or if the duration is unknown
  • Indicated if planning cardioversion on patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship who haven’t received anticoagulation Anticoagulation Pulmonary Hypertension Drugs therapy for at least 3 weeks
  • Used to detect thrombi within the left atrium or left atrial appendage

Other tests to rule out underlying conditions:

• Cardiac enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes → myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction
• BNP BNP A peptide that is secreted by the brain and the heart atria, stored mainly in cardiac ventricular myocardium. It can cause natriuresis; diuresis; vasodilation; and inhibits secretion of renin and aldosterone. It improves heart function. It contains 32 amino acids. Renal Sodium and Water Regulation → heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR)
• TSH/fT4 → hyperthyroidism Hyperthyroidism Hypersecretion of thyroid hormones from the thyroid gland. Elevated levels of thyroid hormones increase basal metabolic rate. Thyrotoxicosis and Hyperthyroidism
• CBC → infection/ sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock
• BUN, creatinine → kidney function
• CT pulmonary angiography Angiography Radiography of blood vessels after injection of a contrast medium. Cardiac Surgery → pulmonary embolism Pulmonary Embolism Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Pulmonary Embolism
• Electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes ( potassium Potassium An element in the alkali group of metals with an atomic symbol k, atomic number 19, and atomic weight 39. 10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the water-electrolyte balance. Hyperkalemia, calcium Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Electrolytes, or magnesium Magnesium A metallic element that has the atomic symbol mg, atomic number 12, and atomic weight 24. 31. It is important for the activity of many enzymes, especially those involved in oxidative phosphorylation. Electrolytes) → electrolyte imbalances
• Urine drug screen → cocaine Cocaine An alkaloid ester extracted from the leaves of plants including coca. It is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake. Local Anesthetics, amphetamines Amphetamines Analogs or derivatives of amphetamine. Many are sympathomimetics and central nervous system stimulators causing excitation, vasopressin, bronchodilation, and to varying degrees, anorexia, analepsis, nasal decongestion, and some smooth muscle relaxation. Stimulants, digoxin Digoxin A cardiotonic glycoside obtained mainly from digitalis lanata; it consists of three sugars and the aglycone digoxigenin. Digoxin has positive inotropic and negative chronotropic activity. It is used to control ventricular rate in atrial fibrillation and in the management of congestive heart failure with atrial fibrillation. Its use in congestive heart failure and sinus rhythm is less certain. The margin between toxic and therapeutic doses is small. Cardiac Glycosides, or alcohol
• Exercise testing → ischemic heart disease Ischemic heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease, also guides pharmacotherapy

Management

AF management consists of the following:

• Determination of hemodynamic status
• Rate control OR rhythm control
• Anticoagulation Anticoagulation Pulmonary Hypertension Drugs therapy
• Treatment of the underlying cause

Special considerations:

• Newly discovered AF < 24-48 hours → electrical cardioversion (without anticoagulation Anticoagulation Pulmonary Hypertension Drugs)
• If concurrent WPW syndrome → IV procainamide Procainamide A class ia antiarrhythmic drug that is structurally-related to procaine. Class 1 Antiarrhythmic Drugs (Sodium Channel Blockers) or IV amiodarone Amiodarone An antianginal and class III antiarrhythmic drug. It increases the duration of ventricular and atrial muscle action by inhibiting potassium channels and voltage-gated sodium channels. There is a resulting decrease in heart rate and in vascular resistance. Pulmonary Fibrosis (not nodal blockers)
• Ablative therapy for tracts or pulmonary vein Pulmonary Vein Total Anomalous Pulmonary Venous Return (TAPVR) foci (long-term management)
• Use heparin only if there is a current clot in the atrium.

Differential Diagnosis

The following conditions are differential diagnoses for AF:

• Atrial flutter Atrial flutter Atrial flutter is a regular supraventricular tachycardia characterized by an atrial heart rate between 240/min and 340/min (typically 300/min), atrioventricular (AV) node conduction block, and a “sawtooth” pattern on an electrocardiogram (ECG). Atrial Flutter: an irregular heart rhythm of the atria. It is classified as supraventricular tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children. Symptoms include palpitations Palpitations Ebstein’s Anomaly. Complications include increased risk of stroke and heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR).
  • Key difference: Flutter is a regular Regular Insulin rhythm whereas fibrillation is irregular. 
• Paroxysmal supraventricular tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children: a type of supraventricular tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children characterized by narrow QRS complexes and a fast heart rhythm, typically between 150 and 240 beats per minute
• Multifocal atrial tachycardia Multifocal atrial tachycardia Tachyarrhythmias: a type of atrial arrhythmia characterized by rapid heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology with at least 3 or more P wave P wave Electrocardiogram (ECG) morphologies. It is called multifocal Multifocal Retinoblastoma since the signals arise from various zones within the atria other than the sinus node. 
• Premature Premature Childbirth before 37 weeks of pregnancy (259 days from the first day of the mother’s last menstrual period, or 245 days after fertilization). Necrotizing Enterocolitis atrial contractions: common ectopic beats generated from foci in atria, triggering premature Premature Childbirth before 37 weeks of pregnancy (259 days from the first day of the mother’s last menstrual period, or 245 days after fertilization). Necrotizing Enterocolitis heartbeats