Atrial fibrillation is recognized on ECG by the absence of P waves and presence of fibrillary waves. Sometimes fibrillary waves may be quite fine so as to be almost unrecognizable in certain leads. In such cases, absence of P waves and a totally irregular RR interval will give the clue to the presence of underlying atrial fibrillation. It may be difficult to recognize the irregularity of RR interval when the ventricular rate is fast, especially in a short ECG strip. Looking at a long rhythm strip and close scrutiny of RR intervals to locate 50% variation between the longest and shortest RR intervals is useful in clinching the diagnosis of atrial fibrillation in such cases. In this ECG the diagnosis of atrial fibrillation (AF) is not difficult because the fibrillary waves are coarse and easily visible in leads V1 and V2. Coarse AF indicates atrial enlargement. Such types of atrial fibrillation is likely to be persistent unless the cause of atrial dilatation is reversible with an intervention like balloon mitral valvotomy. Coarse atrial fibrillation can also mimic atrial flutter. Hence some even call it as flitter or flutter-fibrillation .
A study of 811 patients by Yilmaz MB et al  noted that those with coarse atrial fibrillation was more associated with cerebrovascular events than fine AF. They also noted that patients with fine AF was significantly older than those with coarse AF.
Some authors found a single macro re-entrant circuit in the right atrium in cases of coarse atrial fibrillation. But a randomized multicentre trial  failed to show any advantage for cavo-tricuspid isthmus ablation over external cardioversion in maintaining sinus rhythm in the treatment of coarse atrial fibrillation.
Though it has been generally mentioned that coarse atrial fibrillation correlates with the size of the left atrium as well as the etiology, one study did not document the correlation of f waves (fibrillary waves) with left atrial size . But the study showed that coarse f waves were seen more often than fine waves in rheumatic heart disease.
In addition to coarse atrial fibrillation, this ECG also shows lateral ST segment depression and T wave inversion in inferior leads. QRS axis is a bit rightward. R wave progression in poor in leads V1-V3.
Leier CV, Schaal SF. Biatrial electrograms during coarse atrial fibrillation and flutter-fibrillation. Am Heart J. 1980 Mar;99(3):331-41.
Yilmaz MB, Guray Y, Guray U, Cay S, Caldir V, Biyikoglu SF, Sasmaz H, Korkmaz S. Fine vs. coarse atrial fibrillation: which one is more risky? Cardiology. 2007;107(3):193-6.