Atrial Fibrillation Update: A Textbook of Cardiology Praveen Chandra, HK Chopra, GS Wander, Viveka Kumar
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SECTION 1
1Clinical Spectrum of Atrial Fibrillation
  1. Atrial Fibrillation: An Overview
  2. Risk Factors for Atrial Fibrillation
  3. Valvular Atrial Fibrillation: How is It Different from Nonvalvular Atrial Fibrillation?
  4. Homocysteine and Atrial Fibrillation
  5. Vitamin D Deficiency and Atrial Fibrillation
  6. Electrolyte Imbalance and Atrial Fibrillation
  7. Anemia and Atrial Fibrillation
  8. Sepsis and Atrial Fibrillation
  9. Obstructive Sleep Apnea and Atrial Fibrillation
  10. Air Pollution and Atrial Fibrillation: Present Status and Future Directions
  11. Predictors of Stroke in Atrial Fibrillation
  12. Atrial Fibrillation: Clinical Spectra
  13. Syncope and Atrial Fibrillation
  14. Chronic Kidney Disease and Atrial Fibrillation
  15. Hyperthyroidism and Atrial Fibrillation
  16. Hypothyroidism and Atrial Fibrillation
  17. Hypertension, Atrial Fibrillation and Other Cardiac Arrhythmias
  18. Increased Carotid Intima-media Thickness and Atrial Fibrillation
  19. Nuclear Scan and Atrial Fibrillation
  20. Women and Atrial Fibrillation
  21. Risk Factors for Stroke in Atrial Fibrillation
  22. Rheumatic Heart Disease and Atrial Fibrillation
  23. Atrial Fibrillation in Children
  24. Peripartum Cardiomyopathy and Atrial Fibrillation
  25. Stable Coronary Artery Disease and Atrial Fibrillation
  26. Histopathology of the Atria in Mitral Stenosis with Respect to the Underlying Rhythm: Implications for Treatment
  27. Atrial Fibrillation and Heart Failure
  28. The Mind-Heart Connection and Atrial Fibrillation
  29. Initiators, Triggers and Promoters of Atrial Fibrillation
  30. Pregnancy and Atrial Fibrillation
  31. Cardiac Infiltrating Disorders and Atrial Fibrillation
  32. Marfan's Syndrome and Atrial Fibrillation
  33. Mitral Valve Prolapse and Atrial Fibrillation
  34. Idiopathic Dilated Cardiomyopathy with Atrial Fibrillation
  35. Dilated Cardiomyopathy and Atrial Fibrillation
  36. Atrial Fibrillation and Hypertrophic Cardiomyopathy
  37. Atrial Fibrillation in Tropical Endomyocardial Fibrosis
  38. Chronic Obstructive Pulmonary Disease and Atrial Fibrillation
  39. Obesity and Prognosis in Atrial Fibrillation:With or without Oral Anticoagulants
  40. Takotsubo Mimicking Acute Myocardial Infarction and Atrial Fibrillation
  41. Atrial Fibrillation in Pulmonary Arterial Hypertension2

Atrial Fibrillation: An OverviewCHAPTER 1

Rohit Goel,
Nagender S Chouhan,
Praveen Chandra
 
INTRODUCTION
Atrial fibrillation (AF) is the most common sustained arrhythmia-needing hospital admissions.1 It is characterized by low amplitude fibrillatory waves on ECG and an irregularly ventricular rhythm.
Its incidence increases with advancing age as shown in the ATRIA2 study, a cross-sectional study of around 1.9 million subjects in the United States. The overall prevalence of AF was 1%; 70% were at least 65 years old and 45% were ≥75 years old. The prevalence of AF ranged from 0.1% among adults less than 55 years of age to 9% in those ≥80 years of age. Its prevalence is also higher in men than women (1.1 vs 0.8%), a difference which is seen across all age groups. Among subjects over 50 years, AF was more frequent in Whites than Blacks (2.2 vs 1.5%).
Incidence: It also increases with advancing age and varies from 0.5 per 1000 person-years before age 50 to 9.7 per 1000 person years after age 70.3
The lifetime risk for the development of AF was analyzed in the Framingham Heart Study.4 A total of 8725 patients were followed from 1968 to 1999 of which 936 developed AF. The risk of developing AF from age 40 to 95 was 26% for men and 23% for women.
 
RISK FACTORS
Hypertensive heart disease and coronary heart disease (CHD) are the most common chronic disorders seen in patients with AF in developed countries. However in developing countries, rheumatic heart disease, although uncommon in developed countries, is associated with a much higher incidence of AF.
In a study of approximately 1100 patients with rheumatic heart disease, the prevalence varied with the type of valve disease:5
Mitral stenosis (MS), MR, and tricuspid regurgitation– 70%
MS and MR – 52%
Isolated MS – 29%
Isolated MR – 16%
Other risk factors include heart failure, hypertrophic cardiomyopathy (HCM), sleep apnea, obesity, diabetes mellitus, thromboembolism, congenital heart disease, chronic kidney disease, cardiac and noncardiac surgery, hyperthyroidism, and alcohol, familial and genetic mainly polygenic inheritance.
 
CLASSIFICATION
Atrial fibrillation classification is based on American Heart Association/American College of Cardiology/Heart Rhythm Society guidelines on AF management:6
  • Paroxysmal (i.e. self-terminating or intermittent) AF: It is defined as AF that terminates spontaneously or with intervention within seven days of onset. Episodes may recur with variable frequency.
  • Persistent AF: It is defined as AF that fails to self-terminate within seven days. Episodes often require 4pharmacologic or electrical cardioversion to restore sinus rhythm. While a patient who has had persistent AF can have later episodes of paroxysmal AF. AF is generally considered a progressive disease.
  • Long-standing persistent AF: AF that has lasted for more than 12 months.
  • Permanent AF: This term is used to identify individuals with persistent atrial fibrillation where a joint decision by the patient and clinician has been made to no longer pursue a rhythm control strategy.
  • Lone AF: AF seen in patients less than 60 years with no evidence of structural heart disease. This entity carries a low risk of thromboembolic complications obviating the need for therapeutic anticoagulation.
 
CLINICAL FEATURES
Typical symptoms include palpitations, tachycardia, fatigue, weakness, dizziness, lightheadedness, reduced exercise capacity, increased urination, or mild dyspnea.
More severe symptoms include dyspnea at rest, angina, presyncope, or infrequently, syncope.
In addition, some patients may present with an embolic event or left sided/right-sided heart failure (as manifested by peripheral edema, weight gain, and ascites).
A complete history and physical examination should be performed for all the patients to look for any reversible causes of AF. Diagnosis is confirmed on 12 lead ECG. Echocardiography is performed to rule out any structural heart disease, evaluate the size of left and right atria and left ventricular function. Trans-esophageal echo is done to look for any left atrium/left atrial appendage (LA/LAA) clot prior to cardioversion.
In case of intermittent AF diagnosis can be established by 24 hours Holter or prolonged recording by using external loop recorder.
 
MANAGEMENT
Adequate management of AF patients is very essential. It is associated with five-fold increased risk for stroke and two fold increased risk for all-cause mortality. It is also associated with increased risk of heart failure.
Patients with AF have two management issues. One is the need for therapeutic anticoagulation and other is the treatment of arrhythmia per se either by a rate control strategy or rhythm control.
The need for therapeutic anticoagulation has been facilitated by the use of CHA2DS2-VASc score. With score more than 1 indicating the need for therapeutic anticoagulation. Also higher is the score more is the risk for thromboembolic complications and more necessity in need of anticoagulation.
Regarding rate control versus rhythm control strategy, it is determined based on the severity of symptoms, presence of structural heart disease, and adequacy of rate control during episodes of atrial fibrillation, and the patient's preference for using antiarrhythmic drug therapy or undergoing ablation-based interventions.
To summarize, it is the most common arrhythmia seen in clinical practice and needs optimal medical attention. If left untreated or inadequately treated, it may lead to severe morbidity and increased mortality. Physician's inertia in initiating anticoagulation due to bleeding risk also needs to be addressed. Hence, a team approach which involves primary care physicians as well as the cardiologists is needed for the adequate management of such patients.
REFERENCES
  1. Lip GYH, Bawden L, Hodson R, Rutland E. Atrial fibrillation amongst the Indo-Asian general practice population. The West Birmingham atrial fibrillation project. Int J Cardiol. 1998;65:187–92.
  1. Go AS, Hylek EM, Phillips KA, Chang Y, Henault LE, Selby JV, Singer DE. Prevalence of diagnosed atrial fibrillation in adults: national implications for rhythm management and stroke prevention: the AnTicoagulation and Risk Factors in Atrial Fibrillation (ATRIA) Study. JAMA. 2001;285(18):2370.
  1. Krahn AD, Manfreda J, Tate RB, Mathewson FA, Cuddy TE. The natural history of atrial fibrillation: incidence, risk factors, and prognosis in the Manitoba Follow-Up Study. Am J Med. 1995;98(5):476.
  1. Lloyd-Jones DM, Wang TJ, Leip EP, Larson MG, Levy D, Vasan RS, D'Agostino RB, Massaro JM, Beiser A, Wolf PA, Benjamin EJ. Lifetime risk for development of atrial fibrillation: the Framingham Heart Study. Circulation. 2004;110(9):1042.
  1. Diker E, Aydogdu S, Ozdemir M, Kural T, Polat K, Cehreli S, Erdogan A, Göksel S. Prevalence and predictors of atrial fibrillation in rheumatic valvular heart disease. Am J Cardiol. 1996;77(1):96.
  1. January CT, Wann LS, Alpert JS, Calkins H, Cigarroa JE, Cleveland JC Jr, Conti JB, Ellinor PT, Ezekowitz MD, Field ME, Murray KT, Sacco RL, Stevenson WG, Tchou PJ, Tracy CM, Yancy CW, ACC/AHA Task Force Members. 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. Circulation. 2014;130(23):e199.