Atrial fibrillation electrocardiogram

Electrocardiogram
Atrial fibrillation is diagnosed on an electrocardiogram, an investigation performed routinely whenever irregular heart beat is suspected. Characteristic findings are the absence of P waves, with unorganized electrical activity in their place, and irregularity of R-R interval due to irregular conduction of impulses to the ventricles.

EKG is helpful to identify:
 * Rhythm (verify AF)
 * LV hypertrophy
 * P-wave duration and morphology or fibrillatory waves
 * Preexcitation
 * Bundle-branch block
 * Prior MI
 * Other atrial arrhythmias
 * To measure and follow the RR, QRS, and QT intervals in conjunction with antiarrhythmic drug therapy

Summary of Electrocardiographic findings

 * 1) Absent P waves
 * 2) Irregularly irregular ventricular response rate. Regular RR intervals are possible in the presence of AV block or interference due to ventricular or junctional tachycardia.
 * 3) An atrial rate that ranges from 400 to 700 BPM.
 * 4) Sometimes lead V1 may look as though there is atrial flutter. This may be because the electrode overlies a portion of the RA with rhythmic activity.
 * 5) Some authors believe that fine f waves (<.5 mm) are associated with coronary artery disease and that coarse F waves are associated with LA enlargement and rheumatic heart disease.
 * 6) The ventricular rate is usually between 100 and 180 BPM.
 * 7) If the atrial rate is greater than 200 BPM, then consider WPW or an accessory pathway.
 * 8) In the presence of AV junctional disease, the ventricular rate may be below 70 bpm.
 * 9) A rapid, irregular, sustained, wide-QRS-complex tachycardia strongly suggests AF with conduction over an accessory pathway or AF with underlying bundle-branch block.
 * 10) Complete AV block is indicated by a slow ventricular rhythm with a regular RR interval.
 * 11) In patients with electronic pacemakers, diagnosis of AF may require temporary inhibition of the pacemaker to expose atrial fibrillatory activity.
 * 12) Differential diagnosis includes an EKG artifact such as a tremor. The oscillations in this case are largest in the limb leads.

When are electrocardiograms used for screening?
The SAFE trial found that electronic software, primary care physicians and the combination of the two had the following sensitivities and specificities: :
 * Interpreted by software: sensitivity = 83%, specificity = 99%
 * Interpreted by a primary care physician: sensitivity = 80%, specificity = 92%
 * Interpreted by a primary care physician with software: sensitivity = 92%, specificity = 91%

If paroxysmal AF is suspected but the electrocardiogram shows a regular rhythm, episodes may be documented with the use of Holter monitoring (continuous ECG recording for 24 hours). If the symptoms are very infrequent, longer periods of continuous monitoring may be required.

External EKG Sources

 * John Vozenilek's (MD) ECG Collection
 * ECGpedia