Cardiac Arrhythmias: Management of Atrial Fibrillation in the Critically Ill Patient
Thomas C. Crawford, MD, Hakan Oral, MD*
Cardiac Electrophysiology, Division of Cardiovascular Medicine, University of Michigan, CVC 1500 E. Medical Center Drive, SPC 5853, Ann Arbor, MI 48109-5853, USA
Atrial ﬁbrillation (AF) is a common arrhythmia in the ICU, second onlyto ventricular tachycardia. A study of prevalence of arrhythmias showed that AF may occur in up to 31% of patients in medical, cardiac, and surgical ICUs . AF is associated with a signiﬁcantly longer ICU stay. In-hospital mortality associated with acute myocardial infarction (MI) is higher in patients who have AF (25% versus 16%) . AF is associated with a twofold increase in mortality in thecommunity, and it is inﬂuenced by the severity of underlying heart disease [3,4]. It is estimated that 2.2 million people in the United States have AF. The prevalence of this disease increases with age. The burden of AF is expected to rise as population ages, and it will continue to be associated with signiﬁcant health care costs . Etiology and associated conditions AF is associated withvarious cardiac or extracardiac conditions, some of which are chronic, while others are short lived. In the setting of acute illness, AF may present de novo, or it may recur in patients who have a history of AF. Surgery, especially cardiac or thoracic, pulmonary embolism or other pulmonary conditions, myocarditis, electrocution, alcohol consumption, thyroid disorders, and other metabolic conditions maycontribute to the development of AF. AF also often is associated with history of hypertension and coronary artery disease (CAD). Eleven percent of patients presenting with acute MI
* Corresponding author. E-mail address: email@example.com (H. Oral). 0749-0704/07/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.ccc.2007.06.005 criticalcare.theclinics.com
856CRAWFORD & ORAL
develop AF during their hospitalization . Left ventricular (LV) hypertrophy and associated diastolic dysfunction likely play a role in the genesis of AF because of an increase in stretch in the left atrium or the pulmonary veins . Valvular heart disease, especially mitral stenosis and mitral regurgitation resulting in left atrial (LA) dilatation, commonly are associated withatrial arrhythmias. AF also may be related to hypertrophic cardiomyopathy (HCM) or dilated cardiomyopathy, and various forms of congenital heart disease in adults, especially atrial septal defect. Less common causes of AF include restrictive cardiomyopathies (such as amyloidosis, hemochromatosis, and endomyocardial ﬁbrosis), pericarditis, and cardiac tumors. The known causes of AF are listed in Box1. Among noncardiac chronic conditions, obesity is an important, recently identiﬁed risk factor for developing AF [8,9]. There is a direct relationship between LA size and body mass index (BMI). An association between obstructive sleep apnea (OSA) and AF also has been reported . The term lone AF is used to describe AF in individuals younger than 60 years of age who have no clinical orechocardiographic evidence of cardiac disease. In approximately 45% of patients who have paroxysmal AF and 25% of patients who have chronic AF, no cardiac disease can be identiﬁed . Fluctuations in autonomic tone appear to play a role in the initiation of AF, especially in structurally normal hearts. Both vagal and sympathetic tone may surge in the minutes that precede initiation of AF [12,13].Deﬁnitions Various terms have been used in the literature to describe patterns of AF occurrence. The North American Society of Pacing and Electrophysiology and the European Society of Cardiology recently endorsed a new nomenclature . Episodes are classiﬁed as ﬁrst-detected, recurrent, paroxysmal, persistent, or permanent. When a patient has had two or more episodes of AF, AF is considered...