Perioperative Arrhythmias During Thoracic Surgery

Predictive Factors

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. 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. 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. 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. 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. FLOAT NOT FOUND

Table22.1Risk of Postoperative Atrial Fibrillation by Surgical Procedure

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. 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. ^, Amar et al. 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. In these latter settings, POAF usually occurs beyond the initial postoperative period (first 7 days) after the index surgery.