Atrial Fibrillation: A Review of Treatments and Current Guidelines

Atrial fibrillation is a common disturbance in cardiac rhythm that affects 2.7 million to 6.1 million Americans; these numbers are expected to double in the next 25 years.1 Atrial fibrillation is the most common arrhythmia in the clinical setting.2 Predictors of atrial fibrillation include advancing age, male sex, body mass index (calculated as weight in kilograms divided by height in meters squared) greater than 30, systolic blood pressure greater than 160 mm Hg, hypertension treatment, PR interval greater than 160 milliseconds, significant murmur, and prevalent heart failure.3 Other factors that are associated with atrial fibrillation include diabetes mellitus, hyperthyroidism, obstructive sleep apnea, and alcohol, tobacco, or drug use.1Atrial fibrillation increases morbidity and mortality for patients, and the lifetime risk for atrial fibrillation developing is 1 in 4.3 Acute and critical care nurses working in hospital settings provide care for patients with atrial fibrillation on a daily basis. In this column, we review the pathophysiology, characteristics, descriptive categories, and current treatment guidelines for atrial fibrillation, along with strategies for prevention of thromboembolism.Atrial fibrillation is a supraventricular arrhythmia with uncoordinated atrial electrical activity and uncoordinated motion of the atrial wall. A variety of pathophysiological mechanisms such as structural abnormalities, electrical abnormalities, remodeling,1 and inflammation2 are associated with the development of atrial fibrillation.2 When atrial tissue has structural and/or electro-physiological abnormalities, abnormal impulse formation and/or propagation occurs, resulting in atrial fibrillation.1 The beat-to-beat irregularity of the atrial contractions produces an uncoordinated forward flow of blood into the ventricles. This lack of coordinated blood volume produces an irregular stroke volume with each ventricular contraction, thus producing a variable blood pressure and cardiac output.Atrial fibrillation produces a range of symptoms from none to debilitating.4 Palpitations, fatigue, dyspnea, chest pain, and anxiety are all reported, with fatigue the primary complaint of most patients.5 Susceptibility to atrial fibrillation is increased by any changes that affect the atrial architecture such as inflammation, hypertrophy, and fibrosis.6 Atrial fibrillation is rarely a primary disorder1 and is more likely to be treated successfully, with return to sinus rhythm, if the duration of the atrial fibrillation is less than 6 months.7Electrocardiographic (ECG) findings in atrial fibrillation include irregular R-R intervals, irregular atrial activity, and lack of normal P waves (Figure 1). QRS complexes are usually monomorphic but irregular in rhythm owing to the characteristics of the atrioventricular node. The atrioventricular node serves a gateway function during atrial fibrillation and responds to some electrical stimuli, but not to all electrical impulses generated in the atria. QRS complexes usually look similar unless the refractory period of one of the bundle branches (usually the right bundle branch) is long, in which case QRS morphology may vary from beat to beat with some complexes wide and some narrow (Figure 2). This variability in QRS width is known as aberrant conduction, which is a temporary bundle branch block due to intermittent refractoriness of the bundle branch affected.Assessment of the patient with atrial fibrillation is based on the clinical history and the findings on physical examination, including serial ECGs, with a focus on the risk factors associated with atrial fibrillation. A thorough health history includes current episodes of atrial fibrillation, focusing on onset and duration; aggravating and relieving factors; medical/social history; family history; and a review of systems. Physical assessment findings include an irregular pulse, variation in the auscultation of the first heart sound, and absence of the fourth sound if previously heard during sinus rhythm.1 When a peripheral pulse is palpated, there may be a discrepancy between the apical rate auscultated and the rate palpated; this phenomenon is related to the variation in stroke volume caused by a rapid, irregular heart rate (sometimes referred to as a pulse deficit). Diagnosis is made on the basis of ECG findings.1Cardiac imaging and laboratory tests are done once atrial fibrillation is identified on the ECG. Two-dimensional echocardiography is used to assess for structural heart disease, cardiac wall motion, and atrial size in all patients with newly identified atrial fibrillation.1 Laboratory studies include serum levels of electrolytes; thyroid, renal, and hepatic function tests; and a complete blood cell count.1 Additional studies include transesophageal echocardiography to identify structural or valvular abnormalities or the presence of a clot, chest radiography, continuous ECG monitoring (eg, with an event monitor that can be used to identify paroxysmal atrial fibrillation), and exercise tests to assess rate control and reproduce exercise-induced atrial fibrillation.1The most recent guideline from the American College of Cardiology (ACC), the American Heart Association (AHA), and the Heart Rhythm Society (HRS) with collaboration from the Society of Thoracic Surgeons (STS) categorizes atrial fibrillation by duration of the episode: paroxysmal, persistent, longstanding persistent, permanent, and nonval-vular.1Paroxysmal atrial fibrillation occurs spontaneously and terminates either spontaneously or with interventions within 7 days.1Persistent atrial fibrillation continues for more than 7 days despite use of rhythm control drugs or attempts at direct current car-dioversion.1Long-standing persistent atrial fibrillation has a duration of more than 12 months.1 The term permanent atrial fibrillation is the result of a decision made between the patient and the clinician that no further interventions to try to restore or maintain sinus rhythm will be pursued. The decision to pursue treatment can change if the patient’s clinical condition changes, or if new therapies become available. The term permanent atrial fibrillation reflects the past course of therapy, rather than a physiological finding.The terms nonvalvular and valvular atrial fibrillation have no uniform definitions,8 but valvular atrial fibrillation is a description used when the suspected cause of atrial fibrillation is related to an implanted heart valve, mitral valve repair, or rheumatic heart disease.1 In the past, the term lone atrial fibrillation was used to describe atrial fibrillation in persons who have no known cause for the condition. This term is not used in the current simplified scheme of definitions in the guidelines.1Guidelines for management of atrial fibrillation were published by the AHA/ACC/HRS, with collaboration from the STS in 2014,1 the European Society of Cardiology (ESC) in 2012,8 and the Canadian Cardiovascular Society in 2012.9 In the past, the ESC published guidelines jointly with the ACC and AHA, but because of regulatory, legal, and practice differences in Europe, the ESC published a separate set of guidelines with the most recent update.10 Although the guidelines have many similarities, they do contain some conflicting recommendations. The ESC guidelines recommend use of either the CHADS2 (congestive heart failure, hypertension, age at least 75 years, diabetes mellitus, prior stroke, transient ischemic attack, or thromboembolism [doubled]) scoring system or the CHA2DS2-VASc (congestive heart failure, hypertension, age at least 75 years [doubled], diabetes mellitus, prior stroke or transient ischemic attack, or thromboembolism [doubled], vascular disease, age 65–74 years, sex category) scoring system for calculating stroke risk.8Although the guidelines have differences, most recommendations are either identical or nearly identical where the evidence is strong. Differences become more pronounced when expert consensus is required or differences in regulatory practice exist.10 For example, the ESC recommends oral anticoagulation in patients with a CHA2DS2-VASc of 1 and the AHA/ACC/HRS recommend oral anticoagulation in patients with a score of 2 or more.1,8 Clinicians should continue to base patients’ treatment on clinical assessment and response to treatment and should use guidelines for reference and direction.Atrial fibrillation causes an irregular emptying of the atria because of lack of organized atrial contractions. Atrial fibrillation increases a patient’s risk of stroke by 5-fold1 because of the risk of thromboembolism. Uneven, static blood flow creates conditions that promote clot formation in the atria, especially in the left atrial appendage, a small sac-like structure. The appendage is sometimes removed or sutured closed during heart surgery to prevent future clot formation. The risk for stroke in patients with atrial fibrillation who do not receive anticoagulation therapy is 1.5% for those aged 50 to 59 years and escalates to 23.5% for those aged 80 to 89 years.11 Identifying those at risk for stroke and ensuring appropriate treatment is vital in reducing morbidity and mortality and improving quality of life for patients with atrial fibrillation.The risk for stroke should be assessed by using the CHA2DS2-VASc score for patients with nonvalvular atrial fibrillation.1 The CHA2DS2-VASc is a tool designed to assign risk on the basis of a patient’s history, with each risk factor assigned 1 point except for age at least 75 years and a history of stroke, temporary ischemic attack, or thromboembolism, which are assigned a score of 2 points each. The maximum score is 9, conferring the highest risk for stroke.12For patients who have mechanical heart valves, warfarin is recommended for antico-agulation.1 In patients who have atrial fibrillation without valve disease or replacement, oral anticoagulants are recommended on the basis of the patient’s CHA2DS2-VASc score. When a patient’s CHA2DS2-VASc score is 2 or greater, medication options can include warfarin or a factor Xa inhibitor such as dabigatran, apixaban, or rivaroxaban.1 The goal of therapy is to achieve an international normalized ratio between 2.0 and 3.0 for individuals taking warfarin (2.5–3.5 for most persons with mechanical valves).13 For patients undergoing treatments or interventions that require an interruption of anticoagulation, unfractionated heparin or low-molecular-weight heparin (LMWH) is administered.1 For patients with a CHA2DS2-VASc score of 0, antithrombotic therapy may be omitted.1 A CHA2DS2-VASc score of 1 comes with the recommendation of either no antithrombotic therapy or consideration of treatment with an oral anticoagulant or aspirin.1Initiation of anticoagulation should result from shared decision making with the patient. Determination of which medication to prescribe will depend on each patient’s comorbid conditions and current medications, potential drug interactions, cost, preference of the patient and provider, and the patient’s ability to adhere to the medication regimen, including any dietary restrictions. Strict adherence is critical for the newer anticoagulants (eg, dabigatran, rivaroxaban, and apixaban) because missing 1 dose can increase patients’ risk for a thrombotic event.1 All antithrombotic agents carry a risk of bleeding, and risk stratification schemes such as HAS-BLED have been suggested, although their predictive accuracy is poor.14 Medications used to prevent thromboembolism in patients with atrial fibrillation and considerations for their use are described in Table 1.Nursing care of patients with atrial fibrillation involves monitoring and assisting with 2 medical treatment strategies: heart rate control to maintain hemodynamic stability and rhythm control to safely return the patient’s rhythm to regular sinus rhythm. A number of randomized controlled trials failed to demonstrate the superiority of either rhythm control or rate control in the management of atrial fibrillation.1 The decision to pursue rate control of atrial fibrillation versus conversion to normal sinus rhythm must take into consideration the length of time the patient has been in atrial fibrillation, whether the atrial fibrillation is paroxysmal or persistent, treatments previously attempted, comorbid conditions, and medication interactions.Clinical studies have not shown that either strict or lenient control of heart rate improves mortality, symptoms, hospitalizations, or quality of life.1 However, rate control in patients with atrial fibrillation can reduce morbidity.1 Rate control should be targeted to a heart rate of less than 80/min, but a lenient target of less than 110/min may be reasonable if the patient is asymptomatic and left ventricular function is preserved.1 Control of the ventricular rate can be achieved with β-blockers, calcium channel blockers, and amiodarone. In the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study, β-blockers were the most effective and most commonly used rate control medication for atrial fibrillation.16 In an acute setting, some of these medications can be given via an intravenous route if the patient is hemodynamically stable.Before pursuing pharmacological interventions for rate control in patients with atrial fibrillation, it is important to determine whether preexcitation exists, such as Wolff-Parkinson-White syndrome (Figure 3). In patients with Wolff-Parkinson-White syndrome, electrical signals travel through an accessory pathway between the atrium and the ventricle, rather than through only the atrioventricular node, resulting in preexcitation. In the setting of Wolff-Parkinson-White syndrome, digoxin, calcium channel blockers, and intravenous amiodarone should not be administered because ventricular fibrillation can occur.1 Cardioversion, catheter ablation, or the drugs procainamide or ibutilide are recommended for this rare manifestation of atrial fibrillation.1Pharmacological rhythm control is most often sought with young patients with recently diagnosed atrial fibrillation and those who are unresponsive to or intolerant of rate-control drugs.17 Hospitalization is generally not necessary if the patient is hemodynamically stable. Elderly patients are more likely to require hospitalization when using medications to convert to normal sinus rhythm as opposed to using medications merely to control the ventricular rate in atrial fibrillation.18 Pharmacological control of atrial fibrillation to return to sinus rhythm is most effective when started within 7 days of onset.1 Rhythm control should first focus on identifying and treating reversible or precipitating causes of atrial fibrillation. Pharmacological therapy can then be initiated by using amiodarone, dofetilide, dronedarone, flecainide, propafenone, or sotalol, depending on the patient’s underlying heart disease and comorbid conditions.1 Amiodarone does not have a labeled indication for treatment of atrial fibrillation. When atrial fibrillation is categorized as permanent, rhythm control should no longer be pursued. See Table 2 for medications used for rate and rhythm control.Direct current cardioversion aims to depolarize all of the cardiac cells rapidly and simultaneously in an attempt to return the heart to regular sinus rhythm. The defibrillator is set to deliver the electrical shock in synchrony with the QRS complex, to avoid discharge during ventricular repolarization. For patients in unstable condition, rapid cardioversion is recommended.1 A hemodynamically unstable patient might exhibit chest pain, shortness of breath, changed mentation, or hypotension. For those patients requiring immediate cardioversion, anticoagulation should be initiated as soon as possible and continued for 4 weeks.1In a hemodynamically stable patient with atrial fibrillation, caution should be taken before elective cardioversion. If the duration of atrial fibrillation is 48 hours or longer or the duration is unknown, the risk for embolism of a thrombus from the left atrium into the central circulation is increased. Recommendations for this situation include anticoagulation 3 weeks before and 4 weeks after elective cardioversion.1 As an alternative to the 3 weeks of anticoagulation before cardioversion, a transesophageal echocardiogram can be obtained to determine the presence or absence of atrial clot. If no thrombus is identified, cardioversion can proceed; however, anticoagulation therapy should still be continued after cardioversion.20For episodes of atrial fibrillation less than 48 hours in patients at high risk for stroke, anticoagulation with intravenous heparin, low-molecular-weight heparin, or a factor Xa or direct thrombin inhibitor should be given before or immediately after cardioversion and continued long term.1 Anticoagulation may be omitted for patients who have had atrial fibrillation for less than 48 hours and who are at low risk for stroke.Pulmonary vein isolation (PVI) is a procedure that can be performed during cardiac surgery to interrupt the atrial fibrillation pathways arising around the pulmonary vein in the left atrium. It is offered to patients with atrial fibrillation who are already undergoing cardiac surgery as an option for eliminating atrial fibrillation. The success rate of PVI is 60% to 80% at 1 year.21 PVI may also be performed in the cardiac catheterization or the electro-physiology laboratory. The same atrial fibrillation pathways can be ablated by using radiofrequency energy or cryothermy. The success rate for nonsurgical PVI is 50% to 80%.22For patients who have not responded to pharmacological interventions for rate and rhythm control and who are not undergoing cardiac surgery, ablation of the atrioventricular node and insertion of a permanent pacemaker for ventricular pacing is recommended.1 As this decision is irreversible, education and counseling of the patient should be pursued before intervention. PVI is most often performed in young, healthy patients with paroxysmal atrial fibrillation, so the risks and benefits must be weighed for other populations of patients. Patients who cannot be treated with anticoagulants before and after intervention should not be considered for PVI.1Atrial fibrillation is a common postoperative complication that affects 25% to 50% of patients after open heart surgery.1 Postoperative atrial fibrillation results in longer stays in the intensive care unit and hospital, increased morbidity and mortality, and higher resource utilization.23 Prophylaxis to prevent postoperative atrial fibrillation in cardiac surgery patients by using both pharmacological and nonpharmacological interventions is recommended.24 Preoperative amiodarone reduces the rate of postoperative atrial fibrillation in patients undergoing cardiac surgery, although amiodarone is not labeled for use in atrial fibrillation.1 β-Blockers should be administered as the first treatment, with calcium channel blockers as an option if rate control is not established with β-blockers.1Only a few studies have examined the incidence of atrial fibrillation after noncardiac surgery, including a study25 that showed that patients undergoing abdominal surgery had a high incidence of postoperative atrial fibrillation. Current guidelines make no recommendations regarding treatment of atrial fibrillation following noncardiac surgery.Acute and critical care nurses make their optimal contribution in patient education. Teaching patients how to live with atrial fibrillation or prevent its recurrence begins at the moment that atrial fibrillation is identified. Atrial fibrillation education must be tailored to the patient’s health care literacy level. The importance of medication, including anticoagulants to reduce stroke risk, should be discussed with patients along with any adverse effects of the medications. Patients should be encouraged to keep an accurate and current medication list, including anything they may take over the counter, to reduce the risk of drug interactions. Safety measures discussed should include prevention of and risk for falls and identification of abnormal bleeding for patients taking anticoagulants. Teaching patients how to take their own pulse while in the hospital may be helpful when they call to report any signs or symptoms.26Lifestyle interventions education should encourage patients to pursue a heart-healthy diet and limit caffeine and alcohol.26 Physical activity should be increased with considerations of any comorbid conditions that may limit this. Smoking and its relationship with the perpetuation of atrial fibrillation is unclear, but smoking cessation interventions and education should be offered to all patients with a history of tobacco use.27Patients should be encouraged to report new or returning symptoms to the provider. Nurses should educate and ensure that the patient is able to identify which provider to call and when to seek emergency treatment. Reasons to seek emergency treatment include signs or symptoms of stroke such as severe headache, dizziness, loss of balance, trouble walking, confusion, or changes in vision.28 The FAST acronym (face drooping, arm weakness, speech difficulty, time to call 911) may also be useful for stroke identification.28 Chest pain, including trouble breathing, racing heart, or dizziness, would also prompt emergency treatment.26 Follow-up should be arranged before discharge, and consideration of barriers such as transportation should be addressed. The importance of any laboratory tests should be reviewed with the patient using a method such as teach back that indicates whether the information was understood.Numerous resources for patient education are available, including websites, handouts, support groups, and web chats. Nurses should be aware of patients’ learning preferences and make every effort to offer these services to patients. In its “Get With the Guidelines” program, the AHA states that patients should take an active role in their health care management and offers many strategies on goal ownership.28Acute and critical care nurses provide care for patients with atrial fibrillation through all phases of the disease from diagnosis, through medical and surgical treatment, and the transition into the community. Atrial fibrillation is costly, and the number of persons affected is increasing. The estimated annual treatment cost is $8700 for a patient with the diagnosis, and the estimated cost to the United States health care system is $26 billion annually.1,29 Nursing assessments and interventions including recognition, prompt risk assessment, treatment, and education improve outcomes in patients with atrial fibrillation.30 Focusing on evidence-based care using the most recent guidelines is the key to caring for this complex population of patients.