Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is difficult to treat. It may present with a variety of symptoms ranging in severity form mild to disabling. While some patients get diagnosed at the time of a routine visit and are not aware of their arrhythmia, others may present with palpitations, chest discomfort, dyspnea and syncope. Atrial fibrillation is commonly associated with cardiac and extra cardiac conditions such as valve disease, left ventricular dysfunction, hypertension, diabetes, pulmonary and thyroid disease.
Patients with AF and structural heart disease or hypertension are at a particularly high risk of developing significant functional impairment or frank congestive heart failure. This is related to diastolic dysfunction whereby patients depend heavily on the atrial ‘kick’ and a controlled regular heart rate for ventricular filling. If these conditions are not met, the filling pressure briskly rises leading to pulmonary congestion.
As part of an adaptation response, left atrium may dilate to be able to accommodate a larger volume of blood, compensate for lack of atrial contraction, and moderate the increase in pulmonary pressures. In turn, left atrial enlargement may signify increased atrial scarring and promote atrial fibrillation by providing a suitable electromechanical substrate for reentry.
Unfortunately, AF is not unique to patients with other comorbidities. Patients without any discernable heart disease or systemic conditions may have so called ‘lone’ atrial fibrillation accounting for about 3% of patients with AF. The definition of lone atrial fibrillation varies between publications and typically excludes patients with AF and significant structural heart disease defined as left ventricular ejection fraction less than 40%, moderate or severe aortic or mitral valvular insufficiency or stenosis, or history of prior heart surgery. According to the guideline definition, patients with thromboembolic risk factors of hypertension, diabetes or prior stroke should be excluded along with patients suffering from congestive heart failure, significant pulmonary or thyroid disease. Given accumulating body of evidence linking obstructive sleep apnea (OSA) and atrial fibrillation, patients suffering from OSA should be excluded. Finally, given known association between AF and left atrial enlargement, those with left atrial size greater than normal may be qualified as having plausible etiology for their arrhythmia. While determining left atrial volume index may be the preferred method for identifying such patients, this measurement is frequently lacking in clinical practice leaving the clinicians with left atrial diameter, typically measured during transthoracic echocardiography procedures in the long parasternal axis.
Atrial fibrillation is present in as many as 10% of the octagenarians[6, 9, 10]. Advanced age among patients with AF (greater than 65-75 years of age) is an independent risk factor for embolic events. Accordingly, patients over 75 are not typically classified as having lone arrhythmia.
Credits: Khaykin Y, MD; Friedlander D, BSc; Zarnett L, BSc; Seabrook C, RN; Beardsall M, RN; Feltham S, RN; Tsang B, MD; Wulffhart Z, MD; Pantano A, MD; Verma A, MD.