Supraventricular arrhythmias are the most common rhythm disturbance encountered in postsurgical patients. The incidence of postoperative atrial fibrillation may be as high as 50% after cardiac surgery, 40% after pneumonectomy, and 20% after lung resection. In addition, other postsurgical patients have an incidence of new-onset supraventricular arrhythmias approaching 10%.
Patients who have supraventricular arrhythmias after major noncardiac surgery are at increased risk for stroke and have significantly higher early and late mortality. After cardiac surgery, atrial fibrillation may herald a prolonged intensive care unit (ICU) course, increased risk of stroke, and increased risk of early and late mortality. Cost of care in a patient who has postoperative atrial fibrillation is increased by an average of $10,000. Thus the human and economic toll of this disease entity in the postsurgical patient population is substantial.
What Are the Patient Risk Factors and Perioperative Conditions that Increase the Risk of Atrial Fibrillation?
Multiple risk factors that predispose patients to atrial fibrillation have been identified ( Table 53-1 ). Every 10-year increase in age beyond 30 years is associated with a 75% increase in risk after cardiac surgery. Thus the risk for development of atrial fibrillation in octogenarians may be greater than 50%. A history of cardiac disease (atrial fibrillation, hypertension, valvular disease, and cardiomyopathy) and chronic pulmonary disease are significant factors that predispose to all postoperative dysrhythmias. In addition, obesity and increased body mass index have also been shown to be predictors of postoperative atrial fibrillation. Preoperative consideration of these factors can prompt clinicians to alter the perioperative medical and surgical management in hope of mitigating some of this increased risk.
| Risk Factor | Permanent | Cardiac | Noncardiac |
|---|---|---|---|
| Epidemiologic | |||
| Advanced age | X | X | X |
| Male gender | X | X | X |
| Height | X | ||
| Medical Conditions | |||
| CAD | X | ||
| HTN | X | X | |
| LAE/LVH | X | ||
| CHF | X | X | X |
| Cardiomyopathy | X | ||
| Valvular disease | X | X | X |
| Prior AF | N/A | X | X |
| Myocarditis | X | ||
| CHD | X | ||
| OLD | X | X | X |
| OSA | X | ||
| PVD | X | X | X |
| Obesity | X | X | |
| DM | X | ||
| Hyperthyroidism | X | ||
| Alcohol | X | ||
What Is the Pathogenesis of Postoperative Atrial Fibrillation?
The pathogenesis of atrial fibrillation in the postoperative period is complex and multifactorial. Several disease processes and conditions predispose to atrial enlargement and fibrosis, which provide the substrate for conduction abnormalities. The inflammatory response induced by surgery is associated with increased release of endogenous catecholamines. Elevated levels may be increased further by the administration of exogenous inotropes and vasopressors. These and other factors ( Table 53-2 ) trigger supraventricular arrhythmias by altering atrial refractoriness and conductivity, thereby predisposing to increased automaticity and reentrant rhythms.
| Induction and emergence of general anesthesia |
| Hemodynamic shifts |
| Surgical trauma |
| Manipulation of the heart and pulmonary veins |
| Pain |
| Electrolyte abnormalities (hypokalemia, hypomagnesemia) |
| Hypervolemia (distension of the atria) |
| Subtherapeutic levels of antiarrhythmics (i.e., beta blockers) |
| Administration of catecholamine inotropes |
| Pulmonary insufficiency (dyspnea, weaning from ventilator) |
The type of surgery performed has a marked impact on the incidence of perioperative atrial fibrillation. In patients undergoing intrathoracic procedures, direct surgical manipulation or compression of the atria and/or pulmonary veins contributes to the pathogenesis. During cardiac surgery, myocardial ischemia and ventricular dysfunction can lead to atrial dilation and elevation of atrial pressures that further contribute to atrial irritability. Although the data in general surgery patients are not as robust as in cardiac surgical patients, minimally invasive laparoscopic techniques may decrease the risk for postoperative atrial fibrillation when compared with open approaches. This finding has been taken to imply that attenuation of the inflammatory and stress responses after surgery may decrease the risk of developing postoperative supraventricular arrhythmias, but this hypothesis is not currently supported by data.
What Strategies Are Effective for the Prevention of Postoperative Atrial Fibrillation?
Although atrial fibrillation in postsurgical patients has long been recognized, the implementation of prophylactic strategies to prevent new or recurrent arrhythmias has just recently gained traction. As knowledge of causative factors and the resulting pathophysiology continues to evolve, the pool of potentially beneficial interventions has broadened. Conceptually, prophylactic strategies against atrial fibrillation fall into one of five categories: antiarrhythmic agents, electrolyte repletion or maintenance, atrial pacing, modulation of the inflammatory response to surgery, and alterations of surgical technique. In general, the utility of prophylactic strategies has been most thoroughly evaluated in patients after cardiac surgery. Therefore considerations pertaining to specific risk and pathophysiology in this population must be considered before extrapolating data to the general surgical population.
Antiarrhythmic Agents
Beta Blockers
Considering the inciting role of increased sympathetic tone in the pathogenesis of atrial fibrillation, it is not surprising that beta-blocker administration for postoperative prevention has been extensively examined. Many studies have confirmed the utility of prophylactic beta blockers to limit the occurrence of postoperative atrial fibrillation. In a meta-analysis of 27 randomized trials published in 2002, Crystal et al. found that beta blockers reduced the risk for development of atrial fibrillation after cardiac surgery by more than 60% (relative risk [RR], 0.39; 95% confidence interval [CI], 0.28 to 0.52). These findings were reaffirmed in a 2004 meta-analysis of 58 trials by the same author. The antiarrhythmic benefit was observed when beta antagonists were started before or immediately after surgery and was independent of the agent or dose used. More recently, a meta-analysis comprising 33 studies and 4698 subjects demonstrated a significant atrial fibrillation risk reduction in cardiac surgical patients receiving perioperative beta blockers. On the basis of this evidence, the most recent American College of Cardiology Foundation (ACCF)/American Heart Association (AHA) guidelines for patients undergoing coronary artery bypass graft (CABG) surgery recommend that all such patients receive perioperative beta blockers from 24 hours before surgery onward.
In the postgeneral thoracic (noncardiac) surgery patient population, a meta-analysis of two studies totaling 129 subjects demonstrated that perioperative beta blockade significantly reduced the incidence of postoperative atrial tachyarrhythmias (RR, 0.40; 95% CI, 0.17 to 0.95) but also increased the risk for hypotension and pulmonary edema. The calculated protective effect of beta blockers in some of these trials (and by extension in the meta-analysis) may have been overestimated by failure to adequately account for beta blocker withdrawal in the control groups. Of greater concern, more recent data have uncovered potential adverse outcomes associated with perioperative beta blockade. The PeriOperative Ischemia Evaluation (POISE) trial, a large randomized controlled study (8351 patients) in a noncardiac surgical population, found that perioperative beta blockers decreased the incidence of cardiac arrest (3.6% vs. 5.1%) and myocardial infarction (4.2% vs. 5.7%) but increased the risk of perioperative hypotension, bradycardia, stroke (1.0% vs. 0.5%), and all-course mortality. A post hoc analysis suggested that the increased incidence of clinically significant hypotension, bradycardia, and stroke may contribute to the increased risk for death observed in the treatment group. A meta-analysis of 33 randomized controlled trials totaling 12,306 patients confirmed these findings, in particular further documenting the increased risk of bradycardia, hypotension, and nonfatal stroke observed in the experimental group.
The most recent guidelines from the American Association for Thoracic Surgery on the prevention of postoperative atrial fibrillation in patients undergoing noncardiac thoracic surgery recommend continuation of beta blockers in patients already receiving them. They do not, though, recommend initiation of beta blockers in naïve patients. For patients undergoing noncardiac, nonthoracic surgery, the risk of adverse effects of beta blockers would also appear to outweigh any theoretical reduction in the incidence of postoperative atrial fibrillation in beta blocker naïve patients. However, continuation of long-standing beta blocker therapy through the perioperative period is recommended for cardiac, thoracic, and general surgery patients. Initiation of beta blocker therapy for atrial fibrillation prophylaxis should be reserved for patients undergoing surgical coronary revascularization.
Amiodarone
Amiodarone, one of the most commonly used antiarrhythmic agents in the ICU setting, is frequently the antiarrhythmic of choice in patients with obstructive lung disease or cardiomyopathy. The prophylactic use of amiodarone to prevent postoperative atrial fibrillation has been extensively studied. A recent meta-analysis comprising 33 studies and 5402 subjects demonstrated a significant reduction in the risk for postoperative atrial fibrillation in amiodarone-treated patients undergoing cardiac surgery. However, use of amiodarone is not benign; long-term use of this drug has been associated with hepatic, pulmonary, and endocrine toxicity. In addition, amiodarone administration can cause significant bradycardia, heart block, and hypotension. A meta-analysis of 18 trials (3408 patients) performed to assess the safety of amiodarone to prevent atrial fibrillation after cardiac surgery found an increased risk for bradycardia and hypotension in the amiodarone-treated group but no statistically significant differences in any other measured endpoints (heart block, myocardial infarction, stroke, and death). These findings were most apparent in patients treated with high doses (>1 g per day), with intravenous formulations and in those in whom the drug was initiated in the postoperative period.
The most recent American College of Cardiology (ACC)/AHA guidelines ascribe a class IIA recommendation for postcardiac surgery atrial fibrillation prophylaxis with amiodarone, whereas American College of Chest Physicians (ACCP) guidelines recommend consideration of amiodarone prophylaxis for patients in whom beta blockers are contraindicated. There are insufficient data available to recommend amiodarone prophylaxis for patients undergoing noncardiac surgery.
Sotalol
Sotalol is a class III antiarrhythmic agent that has both beta- and potassium channel–blocking activity. A Cochrane database review of 11 studies with 1609 subjects found significant reductions in the incidence of postoperative atrial fibrillation in patients undergoing cardiac surgery who received sotalol in the perioperative period. Despite these findings, potentially dangerous side effects (QT prolongation, torsade de pointes, hypotension, and bradycardia) have limited the use of this agent in the post–cardiac surgical population. These same concerns make the adoption of sotalol for prophylaxis during noncardiac surgery unlikely at this time.
Calcium Channel Blockers and Digoxin
Few data support the use of other antiarrhythmic drugs for atrial fibrillation prophylaxis. Early data regarding the use of nondihydropyridine calcium channel antagonists in preventing postoperative atrial fibrillation were inconclusive, and an early meta-analysis could not demonstrate benefit. However, a more recent meta-analysis suggests that they may be of some use. A review of four studies in patients undergoing general thoracic surgery found that calcium channel blockers were effective in preventing postoperative atrial fibrillation whereas the most recent randomized controlled trial failed to demonstrate efficacy. Currently, neither the ACCP nor the ACC/AHA guidelines recommend calcium channel blockers for the prevention of atrial fibrillation after cardiac surgery.
Digoxin was at one time advocated as effective prophylaxis against postoperative atrial fibrillation. However, the literature does not support its use as detailed in a meta-analysis that could not document that digoxin significantly altered the incidence of postoperative atrial fibrillation after cardiac surgery. In fact, one study noted an increased risk for postoperative atrial fibrillation after thoracic surgery in patients who received digoxin. Although it can be effectively used for rate control of atrial fibrillation, no consensus guidelines recommend the use of digoxin for postoperative atrial fibrillation prophylaxis.
Electrolyte Repletion and Maintenance
Magnesium
Electrolyte derangements and membrane instability are postulated to play important roles in the pathogenesis of atrial fibrillation, particularly in the postoperative setting. The importance of the magnesium depletion that typically occurs during cardiopulmonary bypass and after diuretic administration has been studied in patients after cardiac surgery. In a meta-analysis, 16 trials including 2029 patients evaluating the use of prophylactic magnesium were identified. Supraventricular arrhythmias occurred significantly less often in patients treated with magnesium compared with controls (23% vs. 31%). A more recent Cochrane review of 19 studies and 2988 subjects demonstrated similar reductions in patients treated with supplemental magnesium during or after cardiac surgery. It remains unclear whether avoidance of hypomagnesemia or achievement of supernormal magnesium levels was responsible for the observed benefit. Nonetheless, current guidelines of the ACCP recommend maintenance of serum magnesium levels in the normal range after cardiac surgery and suggest that empirical supplementation be considered in this high-risk population.
Atrial Pacing
Atrial pacing has been proposed as a strategy to decrease the incidence of atrial fibrillation after cardiac surgery. It is theorized that overdrive suppression of supraventricular foci may retard the development of atrial fibrillation in the immediate postsurgical period. Heterogeneity within the literature examining pacing for atrial fibrillation prophylaxis makes interpretation of the data challenging. Nonetheless, several meta-analyses have been published. In a review of 13 prospective randomized controlled trials in which right atrial pacing, left atrial pacing, or biatrial pacing was used, Archbold and Schilling found that the most significant reduction in postoperative atrial fibrillation occurred in patients receiving biatrial pacing (RR, 0.46; 95% CI, 0.30 to 0.71). Pacing protocols varied but usually were set 10 to 20 beats above the intrinsic rate for a period ranging from 1 to 5 days. Atrial pacing after cardiac surgery appears to be efficacious in preserving sinus rhythm, but identification of the optimal site and pacing algorithm is limited by the lack of large, well-controlled studies.
Although potentially advantageous, this strategy has not been explored in the non–cardiac surgery population. Pacing is limited to patients with implanted pacemakers and those with transvenous or temporary epicardial pacing wires placed after cardiac surgery.
Modulation of the Inflammatory Response to Surgery
Given the role that the inflammatory response seems to play in the pathogenesis of postoperative atrial fibrillation, various interventions targeting this response have been used in efforts to reduce risk.
Corticosteroids
A meta-analysis of 50 randomized controlled trials of prophylactic steroid administration for patients undergoing cardiac surgery demonstrated a significant reduction in postoperative atrial fibrillation in patients receiving steroids (25.1% vs. 35.1% incidence). Conversely, the Dexamethasone in Cardiac Surgery (DECS) study, a large, multicenter, randomized controlled trial of dexamethasone versus placebo, failed to demonstrate a similar response in patients receiving 1 mg/kg of dexamethasone. The Steroids In caRdiac Surgery (SIRS) trial currently underway across 82 centers in 18 countries may help clarify the risks and benefits of methylprednisolone administration for cardiac surgical patients. Given the potential risks of routine administration of corticosteroids (hyperglycemia, increased risk of infection), they are not currently recommended for postoperative atrial fibrillation prophylaxis.
Statins
In addition to their effects on lipid profiles, statins have known anti-inflammatory effects that are thought to contribute to the observed reduction in new-onset atrial fibrillation. A meta-analysis of 3 randomized controlled trials and 16 observational studies comprising 31,725 patients found that the incidence of postoperative atrial fibrillation after cardiac surgery was significantly reduced by statins (odds ratio [OR], 0.67; 95% CI, 0.51 to 0.88). Interestingly, a meta-analysis examining data on patients undergoing either isolated CABG or isolated aortic valve replacement (AVR) demonstrated a reduction in atrial fibrillation in the CABG group but not in the AVR group. Current ACCF/AHA recommendations call for perioperative statins in all patients with CABG regardless of baseline lipid profile. Evidence is currently lacking to recommend statins for atrial fibrillation prophylaxis for patients undergoing non-CABG surgery.
Epidural Analgesia
Epidural analgesia modulates the sympathetic nervous system and the inflammatory response to surgery. There is some evidence that use of epidural analgesia in patients undergoing noncardiac surgery under general anesthesia reduces the risk of postoperative atrial fibrillation. For example, a meta-analysis of 9 studies and 2016 subjects demonstrated a statistically significant reduction in the incidence of atrial fibrillation in patients receiving epidural analgesia for noncardiac surgery when compared with controls (20.1% vs. 25.4%). Although these limited data are of interest, more robust evidence is required before recommending perioperative epidural analgesia for routine prophylaxis of atrial fibrillation before general or thoracic surgery.
Colchicine
Colchicine is a powerful anti-inflammatory drug that inhibits neutrophil activity. The COPPS-1 (COlchicine for Prevention of Postcardiotomy Syndrome) trial demonstrated a significant reduction in postoperative atrial fibrillation in patients receiving the drug 3 days after undergoing cardiac surgery. Because of study design, efficacy in preventing early-onset (postoperative days 1 to 2) atrial fibrillation was not demonstrated. The recently published COPPS-2 trial failed to show a statistically significant reduction in early postoperative atrial fibrillation in patients receiving colchicine but demonstrated an increased risk of gastrointestinal complications of the drug. Although current AHA/ACC/Heart Rhythm Society (HRS) guidelines ascribe a class IIb recommendation for the use of colchicine for atrial fibrillation prophylaxis in cardiac surgical patients, the COPPS-2 data suggest that colchicine should not be used for this indication.
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