Atrial fibrillation

Nursing, Apr 1997 by Jennifer M Sims, Vickie Miracle

What happens when multiple atrial sites try to act as the heart's pacemakeR

TRIAL FIBRILLATION DEVELOPS WHEN MULTIPLE sites in the atria compete to act as the heart's pacemaker, causing an extremely rapid atrial rate (400 to 700 beats/minute). However, only a small amount of tissue is depolarized, so the atria quiver rather than contracting in unison. Instead of a P wave on the electrocardiogram (ECG), a series of small, irregular fibrillatory (f ) waves appears in the baseline.

Because the heart's ventricles can't tolerate such fast rates, the atrioventricular node protects them by transmitting only a few of the excessive atrial impulses. This causes an irregular ventricular rhythm.

On the ECG, characteristics of atrial fibrillation include:

a wavy baseline of f waves (which may appear rounded, coarse, or almost flat) instead of P waves

an atrial rate of 400 to 700 beats/minute

a slow, normal, or fast ventricular rate. A heart rate below 100 beats/minute is called controlled atrial fibrillation; a rate greater than 100 beats/minute is called uncontrolled atrial fibrillation.

a QRS complex that's typically normal in width

an irregular R-R distance, signifying an irregular ventricular rhythm.

Causes of atrial fibrillation include coronry artery disese, lung disease, heart failure, conduction system disease, and atrial tumors. Symptoms may include palpitations, dizziness, hypotension, chest discomfort, and syncope.

Medications used to treat atrial fibrillation include beta-blockers, calcium channel blockers, digoxin, quinidine, and other antiarrythmic agents. Because quivering atria may allow thrombi to form, the physician may also prescribe an anticoagulant.

Atrial fibrillation may be acute or chronic. Treatment for acute onset aims to control the ventricular response and convert the arrhythmia to a normal sinus rhythm; the goals of chronic treatment are to control the ventricular rat and prevent thrombus formation. If your patient's ventricular rate exceeds 100 beats/minute and he becomes unstable (exhibiting decreased level of consciousness or hypotension), he'll require electrical cardioversion. Closely monitor his heart rate, rhythm, and blood pressure, and look for signs of decreased cardiac output.

Treatment for cardiac arrhythmias is based on the American Heart Association's advanced cardiac life support protocols.

BY JENNIFER M. SIMS, RN, CCRN, BSN Staff Nurse .Tri-County Baptist Hospital LaGrange, Ky. VICKIE MIRACLE, RN, CCRN, EdD

Clinical Coordinator Jewish Hospital Heart and Lung Institute . Louisville, Ky.