When and How Do I Have to Treat the Arrhythmias After Thoracic Surgery?

Increased mortality

Increased pulmonary complications

Hemodynamic deterioration and instability

Induction or exacerbation of heart failure

Increased mean lengths of intensive care unit and hospital stay

Increased mean hospital charges

15.2 Pathophysiology

The clinical manifestation of arrhythmias requires both the presence of a vulnerable cardiac substrate and a trigger that initiates the arrhythmia. Changes in myocardial structure and electrical function constitute the substrate for arrhythmias. Examples for typical arrhythmia substrates are atrial fibroses (favoring atrial fibrillation) and a post-myocardial infarction scar (promoting ventricular tachycardia). The substrate is patient specific but may be modified by the below discussed risk factors. The arrhythmia trigger is defined as a single incident that may set off an arrhythmia. The trigger often takes the form of a premature beat, but may also consist of acceleration or slowing of the heart beat or myocardial stretch [3].

Many perioperative factors can be considered to affect both the arrhythmia substrate and trigger, thereby increasing atrial and ventricular susceptibility to arrhythmias. Risk factors can be classified into patient and surgery related (Table 15.2).

Table 15.2

Risk factors for perioperative arrhythmias, particularly postoperative atrial fibrillation

Patient-related risk factors

Increasing age

Male sex

Structural heart disease (coronary artery disease, valve disease, left ventricular hypertrophy, systolic and diastolic left ventricular dysfunction)

Extracardiac risk factors (obesity, previous stroke, and concomitant lung disease)

Surgery-related risk factors

Surgical trauma (type of procedure/operation, magnitude of lung resection, dissection around the atria, mechanical factors such as instrumentation)

Hemodynamic stress (volume overload or depletion, hypertension, endogenous catecholamines)

Metabolic changes (hypoxemia, hypercarbia, acid-base imbalances)

Electrolyte disturbances (particularly hypokalemia)

Drug effects (beta-blocker withdrawal, digoxin, exogenous catecholamines, phosphodiesterase inhibitors (milrinone), levosimendan)

15.2.1 Patient-Related Risk Factors

Various patient-related clinical and nonclinical risk factors for postoperative arrhythmias have been described. One of the most relevant patient-specific risk factor is age. Increasing age has been demonstrated to be correlated with the development of arrhythmias in the general population as well as in the postoperative setting. Age-related structural and/or electrophysiological changes appear to lower the threshold for atrial and ventricular arrhythmias in the elderly. Since patients undergoing thoracic surgery present with a mean age of 67 years, the risk for the development of arrhythmias is inherently increased [4]. Arrhythmias are most likely to occur in patients with structural heart disease. Patients undergoing noncardiac thoracic surgery often have the substrate of atrial enlargement or elevation in atrial pressures, which predispose to atrial tachyarrhythmias. A history of arrhythmias predisposes to postoperative events. Reported extracardiac risk factors for postoperative atrial tachyarrhythmias include obesity, previous stroke, and history of chronic obstructive pulmonary disease [5]. These risk factors are identical to those known to increase the propensity to the development of atrial fibrillation in the nonsurgical setting.

15.2.2 Surgery-Related Risk Factors

Postoperative arrhythmias are a well-known problem during and after cardiothoracic surgery; however they may also complicate major abdominal surgery. The prevalence depends on the type of operation and the extent of cardiac monitoring after surgery. The prevalence of postoperative arrhythmias may range from 4 % of patients undergoing major general surgery, vascular, and orthopedic surgery to 20 % in patients having elective colorectal surgery [6].

The trauma associated with surgical procedures predisposes patients to atrial and ventricular arrhythmias. Inflammatory mechanisms have been proposed in the development of postoperative arrhythmias since their incidence peaks at 2 to3 days after surgery [5]. Hemodynamic stress favoring arrhythmias may result from surgical trauma, volume overload or depletion, hypertension, and increased levels of endogenous catecholamines. Hypoxemia, hypercarbia, acid-base imbalances, as well as mechanical factors such as instrumentation often predispose to electrophysiological changes favoring the occurrence of arrhythmias. Hypokalemia may provoke postoperative atrial and ventricular arrhythmias [7].

Beta-blocker withdrawal has been associated with an increased rate of postoperative supraventricular tachyarrhythmias. A state of heightened catecholamine effect occurs because chronic beta-blocker use leads to a higher density of beta-adrenergic receptors. Digoxin use has been described as a risk factor for paroxysms of atrial fibrillation after surgery. The intravenous administration of catecholamines and phosphodiesterase inhibitors such as milrinone or enoximone and levosimendan has been reported to cause ventricular premature beats, short runs of ventricular tachycardia, and atrial fibrillation [5].

It is worth noting that the pathogenesis of postoperatively occurring atrial and ventricular arrhythmias is often multifactorial; it involves some or all of the mentioned mechanisms.

15.3 Atrial Fibrillation and Other Supraventricular Arrhythmias

Isolated atrial premature beats are very common after thoracic surgery and are often related to electrolyte or other metabolic imbalances. Atrial premature beats are usually readily identified by surface ECG or continuous telemetric monitoring. Paroxysmal supraventricular tachycardia develops in about 3 % of patients undergoing general surgery. The most frequent sustained arrhythmia is atrial fibrillation. The incidence varies widely (from 12 to 44 %) depending on the type of surgery and patient characteristics. In an analysis of 2588 patients undergoing noncardiac thoracic surgery, the incidence of postoperative atrial fibrillation was 12.3 % [8]. In a multivariate analysis, significant risk factors for the occurrence of atrial fibrillation were male sex (relative risk (RR) 1.72), advanced age (RR in patients with age 70 or grater 5.3), a history of congestive heart failure (RR 2.51), a history of arrhythmias (RR 1.92), a history of peripheral vascular disease (RR 1.65), resection of mediastinal tumor or thymectomy (RR 2.36), lobectomy (8.91), bilobectomy (7.16), pneumonectomy (8.91), esophagoectomy (2.95), and intraoperative transfusions (1.39) [9].

Patients with atrial fibrillation have longer mean intensive care unit and hospital stays. Mean hospital charges are more than 30 % higher when compared with patients without atrial fibrillation. Importantly, an increased mortality in patients with postoperative atrial fibrillation has been demonstrated [10]. However, since many patients with postoperative atrial fibrillation have complex comorbidities, it is not clear to what extent the arrhythmia itself contributes to this increase in mortality [4].

With the aim to facilitate preoperative risk stratification, thoracic surgical procedures were recently divided into low- (<5 %), moderate- (5–10 %), and high- (>15 %) risk groups based on their expected incidence of postoperative atrial fibrillation (Table 15.3). In moderate- and high-risk patients, extended ECG monitoring is recommended (e.g., postoperative telemetry for 48–72 h) [11, 12].

Table 15.3

Risk stratification of thoracic surgery procedures for their risk of postoperative atrial fibrillation

Low-risk procedures (<5 % incidence)	Intermediate-risk procedures (5–15 % incidence)	High-risk procedures (>15 % incidence)
Flexible bronchoscopy with and without biopsy Photodynamic therapy Tracheal stenting Placement of thoracostomy tube or PleurX catheter (CareFusion Corporation, San Diego, California) Pleuroscopy, pleurodesis, decortication Tracheostomy Rigid bronchoscopy Mediastinoscopy Thoracoscopic wedge resection Bronchoscopic laser surgery Esophagoscopy/PEG/esophageal dilation and/or stenting	Thoracoscopic sympathectomy Segmentectomy Laparoscopic Nissen fundoplication/myotomy Zenker diverticulectomy	Resection of anterior mediastinal mass Thoracoscopic lobectomy Open thoracotomy for lobectomy Tracheal resection and reconstruction/carinal resection Pneumonectomy Pleurectomy Volume reduction/bullectomy Bronchopleural fistula repair Clagett window Lung transplantation Esophagectomy Pericardial window

Atrial premature beats usually do not need specific treatment. Paroxysmal supraventricular tachycardia occurs from time to time and treatment is often simple. If vagal maneuvers are not successful, adenosine can be used in increasing doses (Table 15.4). Success rates exceed 95 %. Electrical cardioversion is rarely needed. The management of atrial fibrillation is much more complex.

Table 15.4

Drugs used for postoperative arrhythmias

Drug

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