Management of atrial fibrillation after cardiac surgery—Part I: Pathophysiology and risks

Abstract

TRIAL FIBRILLATION (AF) is the most prevalent cardiac arrhythmia in the general population, affecting 2.3% of individuals between ages 40 and 60 years and 5.9% of individuals 65 years.1,2 The prevalence of AF increases dramatically after cardiac surgery, occurring in patients who were in sinus rhythm before surgery. The absolute frequency of postoperative AF varies depending on demographic characteristics of the population, arrhythmia definitions (ie, paroxysmal and sustained v only sustained), methods of electrocardiogram (ECG) monitoring (ie, daily 12-lead ECGs v Holter monitoring), and type of surgery. In most series that have employed continuous ECG monitoring methods, AF is reported in 30% to 40% of patients after coronary artery bypass graft (CABG) surgery, 40% to 50% after valvular surgery, and 60% of patients after combined CABG and valve surgery. 3-11 In light of the strong association between AF and advancing age, it is likely that the incidence of postoperative AF will continue to increase as the proportion of elderly cardiac surgical patients rises.3-11 Postoperative AF typically occurs 1 to 5 days after surgery, with a peak incidence on postoperative day 2. 3-6 In most patients, AF is well tolerated and self-limiting with 98% of affected patients returning to sinus rhythm 6 to 8 weeks after their operation. 9 In some patients, however, AF may lead to hemodynamic instability, particularly in patients with diastolic dysfunction, who may not tolerate the loss of a synchronous atrial contraction. The development of postoperative AF is associated with 2-fold higher risk of stroke compared with patients remaining in sinus rhythm. 3 Even in the absence of these complications, AF may contribute to higher morbidity and increased health resource usage because of longer hospitalization and other associated complications (eg, need for cardiac pacemakers, congestive heart failure). Patients who develop AF are hospitalized on average 2 to 4 days longer than patients who do not develop this arrhythmia. 3-6 Increased hospital length of stay conservatively contributes to $2,000 of added hospital cost. 4 AF is the leading cause of hospital readmission after discharge following cardiac surgery. 12 Considering the nearly 600,000 cardiac surgical procedures performed annually in the United States, the economic implications of postoperative AF are considerable.13 In this 2-part review, the pathophysiology of and risk factors associated with postoperative AF are discussed first. In the second part (to be published in the next issue), pharmacologic and nonpharmacologic therapies proposed for prevention and treatment of AF are discussed, with an emphasis on safety and efficacy.