Post-op atrial fibrillation (AF, or A-fib) is a well-known complication of open-heart surgery, and is the most common sustained cardiac rhythm disturbance. An aging population and rising chronic heart disease incidence, as well as other factors, have led to a 66% increase in hospitalizations for AF over the past 20 years. Post-op AF results in longer hospital stays, increased costs of hospitalization, increased patient morbidity and mortality (including heart failure and stroke risk), and decreased patient satisfaction. Longer length of stay is associated with increased risk of infection, increased risk of error, and increased use of higher risk medications. In addition, AF is the leading cause of hospital readmission after early discharge following cardiac surgery.
The incidence of post-op AF after open-heart surgery ranges from 20% to 50%, with the highest rates in patients who've undergone valve surgery (especially mitral) or combined surgeries. These rates have changed little over the past 2 decades, and AF incidence is expected to increase at least two- to fourfold by the year 2050.
Relative to other complications after open-heart surgery, such as respiratory distress, septicemia, and wound infections, AF is relatively benign and rather inexpensive on a per patient basis. In fact, AF has often been thought of as an uncomplicated, transient, and self-limiting rhythm disturbance. However, when the overall cumulative impact of AF is tabulated, based on its relative frequency, it's a far greater drain on hospital resources and patient satisfaction. Patient satisfaction is affected by AF persistence (especially paroxysmal AF), the requirement for labs and anticoagulation, symptom management, readmission, complications, and reduction in perceived quality of life.
In this article, I'll examine how AF presents its own unique set of challenges to both the patient and the healthcare team and argue that it should be placed higher on the list of challenges surrounding open-heart surgery. But first, let's briefly review what AF is.
A chaotic heart
AF is defined as chaotic, asynchronous electrical activity in the atrial tissue (see A closer look at AF). It may be sustained or paroxysmal (occurring in bursts). If the ventricular response is greater than 100 beats/minute (uncontrolled AF), the patient may develop heart failure, angina, or syncope. A patient with preexisting cardiac disease may develop shock and severe heart failure.
Post-op AF usually occurs within 5 days after open-heart surgery, with a peak incidence on day 2. The increased length of stay associated with AF ranges from 2 to 5 days.
No crystal ball needed
Pre-op risk factors include:
* male gender
* age older than 65 (In many studies, patient age is noted to be the strongest predictor for AF, with AF incidence increasing dramatically after age 65. After age 80, AF rates can exceed 50%. Each 10-year increase in age is associated with a 75% increase in the risk of developing AF.)
* previous history of AF, hypertension, metabolic syndrome, myocardial infarction, right coronary artery stenosis, mitral stenosis, left atrial enlargement, valvular heart disease, congestive heart failure, or chronic obstructive pulmonary disease
* delay in post-op use of beta-blockers and angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) (A delay in post-op ordering may result in drug withdrawal and unmitigated sympathetic activation and/or activation of the atrial angiotensin system.)
* delay in statins (A delay in post-op ordering causes the removal of anti-inflammatory effect.)
* P-wave duration of greater than 140 to 155 milliseconds may help identify susceptible patients who are further exacerbated by fluid overload/atrial stretch; an increase in post-op P-wave dispersion (the difference between the longest and shortest P-wave duration in any leads of a standard ECG) has been shown to be an independent predictor of AF.
Intraoperative risk factors include:
* cardiopulmonary bypass and resulting inflammatory response
* prolonged cross-clamp time, atrial manipulation, and cannulation/venting
* dissection/removal of the anterior epicardial fat pad (contains parasympathetic ganglia)
* euthyroid sick state secondary to cardiopulmonary bypass
* use of an intra-aortic balloon pump (AF in this case may be due to increased patient acuity and ventricular failure).
It has been postulated that off-pump coronary artery bypass graft (CABG) surgery may be associated with significant risk reduction of post-op AF relative to conventional on-pump surgery (such as reduced atrial trauma and inflammation), although the literature is conflicting with respect to this point.
Post-op risk factors include, but aren't limited to:
* catecholamine surges/heightened sympathetic tone
* delayed exaggerated inflammatory response
* electrophysiologic vulnerability/nonuniform atrial conduction (greatest on post-op days 2 and 3)
* electrolyte disturbances (especially potassium and magnesium)
* fluid shifts/atrial stretch
* persistent inotropic support.
The pathogenesis of post-op AF is multifactorial, with many complicating triggers. Any of these post-op triggers combined, even transiently, with the pre-op and intraoperative factors can quickly result in AF.
What can you do?
Even with a prompt response, a longer length of stay can be attributed to patients with AF due to the natural delays in achieving therapeutic goals such as drug initiation and titration, development of drug adverse reactions, and attempts to achieve therapeutic anticoagulation. For elective patients at the highest risk for developing post-op AF, there are several treatment options for prophylactic reduction of AF. The CABG surgery guidelines published by the American College of Cardiology (ACC) and the American Heart Association (AHA), and the AF treatment guidelines published by the ACC, the AHA, and the European Society of Cardiology (ESC) are important reference sources. These guidelines were developed by joint taskforces and include a review of literature over many years.
Beta-blockers are generally considered frontline treatment for post-op AF reduction and are a class I recommendation in the 2006 ACC/AHA/ESC guidelines (see ACC/AHA/ESC guidelines for treating post-op AF). For patients at high risk for developing AF for whom a beta-blocker is contraindicated, amiodarone therapy has been shown to be effective (class IIa recommendation). Amiodarone prophylaxis has been shown to reduce post-op AF from 72% to 8% if instituted preoperatively. Amiodarone trials have been extensive and provide comprehensive information on morbidity; collectively they show a significant reduction in post-op AF, length of stay, ventricular dysrhythmias, and stroke. Sotalol, a class III antiarrhythmic agent with beta-blocking activity, is a class IIb recommendation. However, because amiodarone and sotalol have potentially significant adverse reactions (thyroid, pulmonary, and hepatic), oral beta-blockers are believed to provide the best prophylactic advantage in reducing post-op AF, especially when begun before or immediately after surgery and continued until at least the first post-op follow-up visit.
In addition, studies have discussed statin therapy and its potential role in mediating AF. Results of the Atorvastatin for Reduction of Myocardial Dysrhythmia After Cardiac Surgery, or ARMYDA-3, study showed that 40 mg of atorvastatin, beginning 7 days before surgery, resulted in a 61% reduction in post-op AF and reduced length of hospital stay for elective cardiac surgeries, excluding valve surgery and patients with left atrial enlargement. In the ARMYDA-3 study, patients who were randomly given atorvastatin and also taking beta-blockers showed a 90% risk reduction of post-op AF. In contrast, withdrawal of beta-blockers in the perioperative period doubled the incidence of AF after CABG surgery.
As with any post-op treatment, prophylactic strategies can be tailored to different patient groups. For example, the only intervention for patients with a history of AF may be to restart their pre-op medication earlier.
For patients who do develop post-op AF, there are a multitude of questions surrounding such issues as rate versus rhythm control, electrical versus pharmacologic cardioversion, and anticoagulation. Because many patients will ultimately revert to a normal sinus rhythm within several months of discharge, rate control with beta-blockers is relatively safe and effective. Electrical cardioversion is generally reserved for symptomatic patients. Finally, catheter ablation is an important alternative when available and offered under the care of a properly trained physician, especially for patients with paroxysmal AF or those who can't tolerate warfarin therapy. Anticoagulation has been addressed extensively in several guidelines and should be considered for AF lasting longer than 24 to 48 hours or for patients with multiple episodes.
Take away message
We can't prevent every complication. But we can promise that we'll assess patients for their risk factors, do our best to mitigate what risks we can, and manage the rest closely to help achieve the best possible outcome. This includes being vigilant to avoidable complications such as AF, especially new-onset AF. Nurses are in a key position to assess and manage each patient's AF risks, and effectively advocate for prophylaxis for those patients at highest risk for developing post-op AF. As risk assessment tools become more widely used, the assessment of post-op AF risk will become more streamlined.
ACC/AHA/ESC guidelines for treating post-op AF
* Unless contraindicated, treatment with an oral beta-blocker to prevent post-op AF is recommended for patients undergoing cardiac surgery. (Level of evidence: A)
* Administration of atrioventricular nodal blocking agents is recommended to achieve rate control in patients who develop post-op AF. (Level of evidence: B)
* Pre-op administration of amiodarone reduces the incidence of AF in patients undergoing cardiac surgery and represents appropriate prophylactic therapy for patients at high risk for post-op AF. (Level of evidence: A)
* It's reasonable to restore sinus rhythm by pharmacologic cardioversion with ibutilide or direct-current cardioversion in patients who develop post-op AF, as advised for nonsurgical patients. (Level of evidence: B)
* It's reasonable to administer antiarrhythmic medications in an attempt to maintain sinus rhythm in patients with recurrent or refractory post-op AF, as recommended for other patients who develop AF. (Level of evidence: B)
* It's reasonable to administer antithrombotic medication in patients who develop post-op AF, as recommended for nonsurgical patients. (Level of evidence: B)
* Prophylactic administration of sotalol may be considered for patients at risk for developing AF following cardiac surgery. (Level of evidence: B)
Source: National Guideline Clearinghouse. ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation). http://www.guideline.gov/summary/summary.aspx?doc_id=9661.
did you know?
Although serious and the most common of heart rhythm disorders, patients who experience AF are unaware of its risks, complexities, and consequences and many healthcare providers find its management to be a clinical and health-economic burden, according to a recent survey published in the online edition of EP Europace, a journal of the ESC and the European Heart Rhythm Association. The conclusion? Early detection and an appreciation of risks and consequences are needed to improve AF management and health outcomes. To view the survey, visit http://europace.oxfordjournals.org/content/12/5/626.full.pdf+html?sid=c9bf1666-58ae-4fee-a1af-fb0a5aa6060d.
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