To the Editor:

atrial sensing failure may also be sought in the technical differences between the pacemaker systems utilized and their consequences on the temporal onset of sensing failure. One can assume that with the enhanced sensing capability of their system, sensing failure occurred later in the postoperative course than encountered by us. Our six cases of sensing failure all occurred between 12 and 36 hours after surgery, when postoperative sinus tachycardia is most prominent. Only when the underlying sinus rhythm overrode the upper pacing rate of 110/min, did AF almost invariably ensue. We therefore continue to believe that asynchronous pacing in the presence of an underlying sinus rhythm enhances the risk of developing AF in the early phase after open heart surgery. Recently, results published by other groups have shown either no^ or a nonsignificant^'^ reduction in the incidence of AF with the use of temporary biatrial pacing after heart surgery. Since the former group^ found at least a beneficial trend among patients on postoperative betablocker therapy, it would be of interest to know the proportion of patients on this treatment in the study population of Levy et al. In view of these facts, we think further definition of the possible benefit of this novel treatment among different subgroups of heart surgery patients is required before introduction into wider practice can be considered.