To the Editor: In the management of atrial fibrillation (AF), the dispute between proponents of heart rate control vs. restoration of sinus rhythm (SR) has finally been settled recently by four trials: Pharmacological Intervention in Atrial Fibrillation (PIAF) [1], Strategies of Treatment of Atrial Fibrillation (STAF) [2], Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) [3] and Rate Control versus Electrical Cardioversion (RACE) [4,5]. According to these four trials, there is no difference between the two treatments. However, we have all seen patients whose AF, during acute rate control following intravenous administration of either diltiazem or digoxin, spontaneously reverted to SR. It was very hard for me to convince the young house staff that the restoration of SR in these patients was spontaneous rather than due to diltiazem or digoxin. From the pharmacological standpoint, neither diltiazem nor digoxin is supposed to convert AF to SR; they only slow the ventricular response to AF. As a matter of fact, diltiazem, by shortening the AF cycle length, unwittingly prolongs the duration of recent onset AF [6]. The recent report of the ACUTE trial ancillary study [7] finally provided support to my teaching, because 16% of patients with AF scheduled for electrical cardioversion underwent spontaneous conversion to SR. In another word, one of every six patients with AF scheduled for cardioversion, whether electrical or pharmacological, will spontaneously convert to SR. This phenomenon of coincidence in medicine has been seen in the so-called pseudo-complication of cardiac catheterization [8,9]. Patients suffering from serious cardiovascular diseases may experience major cardiovascular catastrophes (myocardial infarction, thromboembolism, bleeding, ventricular fibrillation, stroke and sudden death) as part of natural history of their disease. If one of these events happens during or in close proximity of cardiac catheterization, either diagnostic or therapeutic, it would be natural to