For atrial fibrillation (AF), including POAF, to develop and be sustained requires the combination of atrial pathology to promote a vulnerable substrate and a trigger to initiate the arrhythmia. Using heart rate variability, the authors have demonstrated the presence of competing autonomic mechanism in the 2 hours before POAF onset.³ In that study, the patients were postoperatively monitored with Holter technology which showed an increased vagal tone in the setting of heightened adrenergic tone occurred before POAF onset, which suggests that a vagal surge could be an important trigger.³ Although the exact mechanisms underlying this are complex and only partially understood, several risk factors associated with AF are highly predictive including: increased age, atrial dilation, pulmonary hypertension, myocardial ischemia, volume overload, and a history of heart failure.¹ Other risk factors, such as postoperative pericarditis, electrolyte imbalance, and hypoxemia, have all been proposed to trigger POAF but have not been proven. In addition, the extent of surgery is highly predictive and is directly related to the risk of POAF. Table 22.1 shows that wedge resections have a low risk of less than 5%, which is similar to patients undergoing nonthoracic surgery. However, anatomic lung resections have a greater than 10% risk of POAF.¹ These large anatomic resections of lung or esophageal structures are associated with higher rates of POAF because of the degree of unavoidable trauma to sympathovagal fibers located within the deep and superficial cardiac plexi.

Studies have shown that whether an operation is performed by open thoracotomy or minimally invasive surgery the rates of POAF are similar. Park et al.⁴ analyzed 122 patients undergoing video-assisted thoracic surgery and 122 patients undergoing an open thoracotomy. AF occurred in 12% of patients (15/122) undergoing video-assisted thoracic surgery and 16% of patients (20/122) undergoing thoracotomy (P = .36). Length of stay for patients that developed AF was greater in both video-assisted thoracic surgery (6.0 ± 1.5 days vs. 4.7 ± 2.5 days) and thoracotomy groups (9.2 ± 4.3 days vs. 6.8 ± 3.6 days). The authors concluded that regardless of surgical approach, AF after lobectomy occurred with equal frequency. This supports the theory that autonomic denervation and stress-mediated neurohumoral mechanisms are responsible for the pathogenesis of postoperative AF. Prophylaxis regimens against AF should be the same for either operative approach.

Although use of transthoracic echocardiography before surgery and presence of indices of atrial dysfunction are more sensitive than preoperative brain natriuretic peptide, the latter blood test is easier to perform and does not require expertise to acquire and analyze complex echocardiography.^5,6 Amar et al.⁷ most recently created an online prediction model that incorporates age, BMI, history of AF, extent of surgery, and preoperative BNP for quick bedside calculation. This model is also displayed graphically in Fig. 22.1 for visual estimation. Finally, POAF is also correlated strongly with other complications that are sources of sympathetic stress, such as pneumonia, sepsis, and systemic inflammation.⁸ In these latter settings, POAF usually occurs beyond the initial postoperative period (first 7 days) after the index surgery.

Monitoring

A common clinical question is how to determine who should be monitored with telemetry postoperatively, which has the practical implication of what inpatient units constitute a safe disposition for the patient. The 2014 American Association of Thoracic Surgeons (AATS) guidelines recommend continuous electrocardiogram monitoring for 48 to 72 hours for all patients with more than intermediate risk (>5%), that is, all patients undergoing a segmentectomy or larger resection, if their CHA₂DS₂-VASc score is 2 or more for stroke (Fig. 22.2), or if they have a history of AF.¹

Prevention

Given the common incidence of POAF complicating the postoperative course, it stands to reason that an effective prevention program would assist in the management of these patients. In pursuit of a prevention strategy, several approaches have been tried but the ideal solution remains elusive. There is a lack of data confirming that prophylaxis leads to improved outcomes in thoracic surgery, and many of the recommendations are extrapolated from the cardiac surgery literature. The strongest recommendation with a class I indication is to continue beta blockers, if patients are taking them ­preoperatively for other indications (Fig. 22.3). Furthermore, restarting beta blockers on postoperative day 1 is associated with a lower POAF rate; however no difference was seen if they were restarted on the day of surgery. Khanna et al.⁹ evaluated 1924 patients who did resume beta blockers by the end of postoperative day 1 with 973 patients who had not resumed beta blockers by that time. A secondary matched analysis compared 3198 patients who resumed beta blockers on the day of surgery with 3198 who resumed thereafter. Of propensity score-matched patients who resumed beta blockers by end of postoperative day 1, 4.9% (94 of 1924) developed AF, compared with 7.0% (68 of 973) of those who resumed thereafter. Patients who resumed beta blockers on the day of surgery had an AF incidence of 4.9% versus 5.8% for those who started thereafter. The authors concluded that resuming beta blockers in chronic users by the end of the first postoperative day may be associated with lower odds of in-hospital AF.

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Myasthenia Gravis and Thymectomy Airway Fistulas in Adults High-Frequency Ventilation: Applications in Thoracic Anesthesia Wedge Resection, Lobectomy, Pneumonectomy Hemoptysis, Empyema Tracheal Stents

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