Atrial Fibrillation

Rates of the arrhythmia are growing in the U.S., and nurses should become familiar with treatment plans.

For a printer-friendly version of the test you can print out, complete and mail in to ADVANCE, click here

This offering expires in 2 years: March 3, 2010

The goal of this continuing education offering is to provide nurses with current information on atrial fibrillation. After reading this article, you will be able to:

1. Explain the classifications of atrial fibrillation.

2. List three risk factors for atrial fibrillation.

3. Discuss the treatment options available for pharmacological, surgical and electrical treatment of atrial fibrillation.

You can earn 1 contact hour of continuing education credit in three ways: 1) For im-mediate results and certificate, go to www.advanceweb.com/nurses. Grade and certificate are available immediately after taking the online test. 2) Send this answer sheet (or a photocopy) along with the $8 fee (check or credit card) to ADVANCE for Nurses, Learning Scope, 2900 Horizon Dr., King of Prussia, PA 19406. 3) Fax the answer sheet to 610-278-1426. If faxing or mailing, allow 30 days to receive certificate or notice of failure. A certificate of credit will be awarded to participants who achieve a passing grade of 70 percent or better.

Merion Publications Inc. is an approved provider of continuing nursing education by the Pennsylvania State Nurses Association (No. 008-0-07), an accredited approver by the American Nurses Credentialing Center's Commission on Accreditation. Merion Publications Inc. is also approved as a provider by the California Board of Registered Nursing (No. 13230) and by the Florida Board of Nursing (No. 3298).

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Atrial fibrillation (AF) is the most common arrhythmia found in clinical practice. This condition affects more than 2 million people in the U.S. According to the Framingham Heart Study, AF increases the risk of death by 1.5-1.9 times. The prevalence of AF increases with advancing age. Currently, almost 5 percent of the population over age 69 and 8 percent of the population over 80 are in AF. Given the aging of our population, AF will continue to pose a problem to the medical profession.

AF is defined by the absence of coordinated atrial systole. In AF, multiple reentrant electrical wavelets move randomly around the atria replacing the normal atrial contractory P waves with irregular, chaotic fibrillatory waves. The atrioventricular (AV) node controls the rate at which the atrial electrical impulses are conducted to the ventricles. The AV node has a normal relative refractory period of ²0.20 seconds. AV nodal conduction can be affected by several factors. These factors include alterations in the AV node relative refractory period, hydration status, AV nodal injury and the presence or absence of pharmacologic agents used to help control ventricular response rates. The fibrillatory waves of AF are conducted through the AV node at various intervals based on the AV nodes ability to conduct electrical impulses. AV nodal conduction in AF most commonly results in an irregular ventricular response that often is tachycardic.

A lack of a coordinated atrial contraction in AF creates the potential for pooling of blood in the right and left atria. As a result of the pooling blood, patients with AF are at high risk for thrombus formation in their atria and ventricles. If a clot forms in the right side of the heart and becomes mobile, patients would be at greater risk for a pulmonary embolus. Clots forming in the left side of the heart would predispose the patient to a stroke or peripheral arterial embolization. Approximately 15-25 percent of all strokes annually occurring in the U.S. can be attributed to AF.

Pathophysiology

There are several important contributory risk factors for AF. Cardiac risk factors include long-standing hypertension, ischemic heart disease, CHF, all forms of carditis, cardiomyopathy, all types of infiltrative heart disease and sick sinus syndrome. Respiratory causes of AF include pulmonary embolism, pneumonia and lung cancer.

Non-cardiovascular risk factors include advanced age, history of stroke, hyperthyroidism, low electrolyte levels (potassium, magnesium and calcium), pheochromocytoma, illicit drug and alcohol use, diabetes, electrocution, hypothermia and idiopathic (also known as lone AF). Idiopathic is defined as the absence of known etiologic factors plus a normal ventricular function by echocardiography. Patients with idiopathic AF usually are under age 65. Additionally, patients having undergone cardiac, pulmonary or esophageal surgery have a 20-40 percent incidence of developing AF postoperatively.

Diagnosis of AF can initially be accomplished by ECG monitoring and should be confirmed and documented by a 12-lead ECG. Further studies and tests are dependent on the patient's medical and surgical history. Patients with new-onset AF will undergo a more extensive workup to help determine the cause of AF. Additionally, a patient's stability may affect the extent of workup prior to initiation of treatment.

A full workup should include a chest X-ray and the following labs: CBC, electrolytes, BUN and creatinine, cardiac enzymes and at least one thyroid function test to exclude hypothyroidism as a cause. Digoxin levels should be drawn if the patient was on digoxin therapy and if digoxin toxicity is suspected. In addition, if acute intoxication or illicit drug use is suspected as a possible cause, a toxicology screen or an ethanol level may be appropriate.

For patients who are hemodynamically stable, an echocardiogram is reasonable to evaluate left ventricular function and cardiac chamber size prior to initiation of treatment. Transthoracic echocardiograms are more desirable in AF due to their ability to look for specific evidence of left atrial or ventricular thrombus. In AF, echocardiograms also help rule out valvular heart disease, pulmonary hypertension, left ventricular hypertrophy and pericardial effusions, all of which can predispose a patient to AF.

Patients who present with complaints of sporadic palpitations consistent with possible intermittent episodes of AF may require Holter monitoring (continuous ECG monitoring over a 12- to 24-hour period) or event monitoring on an outpatient basis to help determine if AF is present. Furthermore, for patients who may experience exercise-induced AF or for AF patients for whom ischemic pathology is being ruled out, an exercise stress test may be indicated.

Physical Findings

Physical findings of AF will vary depending on the length of time the patient has been experiencing AF and also the patient's cardiovascular stability while in AF. All patients who are hemodynamically stable should undergo a detailed history and physical prior to treatment. Most symptomatic physical findings exhibited in AF are due to the loss of the atrial contraction, which reduces a patient's cardiac output (amount of blood ejected by he heart each minute) by up to 20-30 percent. The reduced forward movement of blood during the cardiac cycle frequently leads to venous blood congestion in the peripheral and pulmonary vasculature.

The most common cardiovascular finding is an irregular pulse. Other cardiovascular findings, dependent on patient stability, may include hypotension, poor peripheral perfusion (evidenced by mottling or cool extremities), CHF, elevated venous pressures, cyanotic lips, pleural effusions, ascites and peripheral edema. If embolization is suspected, the patient may exhibit signs of a pulmonary embolus, transient ischemic attack (TIA), stroke or peripheral artery embolization.

Classification of AF

AF has previously been classified in a variety of terms familiar to nurses. These terms include acute, chronic, intermittent, paroxysmal and permanent. Recently published guidelines from the American College of Cardiology/American Heart Association (ACC/AHA) and European Society of Cardiology on the treatment of patients with AF suggests AF should be classified into only three patterns: first detectable episode, recurrent AF and persistent AF. This classification scheme only pertains to AF cases not related to reversible causes (e.g., thyrotoxicosis, electrolyte abnormalities, acute alcohol intoxication).

The first detectable episode can occur irrespective of whether the patient is symptomatic or the episode does not require medical intervention to restore sinus rhythm. A patient is deemed to have recurrent AF when they have two or more episodes of AF. If AF continues to be terminated spontaneously, then it is designated as a subclass of recurrent AF called paroxysmal recurrent AF.

When AF becomes sustained, it is then considered persistent AF, regardless of whether AF can be terminated by medical interventions. Persistent AF can occur on either the first presentation of AF or as a result of recurrent episodes of AF. Persistent AF includes patients with longstanding AF in whom electrical termination of AF has not been indicated or attempted. Permanent AF is recognized by the ACC/AHA as an accepted rhythm. The only treatment goals for permanent AF are rate control and anticoagulation.

Medical Treatment

All treatment plans for AF focus on rate control and anticoagulation, with an eventual goal of restoration and maintenance of sinus rhythm. Restoration of sinus rhythm with regulation of the heart rate improves cardiac hemodynamics and the patient's quality of life while reducing the risk of thromboembolic complications. Additional benefits of rhythm restoration focus on maintaining the appropriate physiologic responses to exercise, preserving the contribution of the atrial contraction to cardiac output, and prevention of dilation of the atria and ventricles.

When designing a treatment plan for a patient presenting with AF, the patient's stability must be carefully considered. Instability in AF often is caused by a rapid ventricular response and the patient experiences one or more of the following symptoms and no cause other than AF is present: symptomatic hypotension, altered mental status or loss of consciousness, hypoxia, presence of CHF and acute coronary syndrome with active myocardial ischemia. Myocardial ischemia presents with symptoms such as angina or ECG changes consistent with MI (ST segment depression or elevation). Unstable AF is treated similarly throughout all care settings.

Patients with unstable AF should be assessed for airway compromise and hypoxemia. Oxygen and airway support should be provided as necessary in accordance with ACLS guidelines. If the patient is experiencing hypotension, blood pressure support should be provided with IV fluids or vasopressors. Blood pressure support often is difficult in patients with unstable AF until their heart rate is controlled.


Atrial Fibrillation

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