The classical orientation of antiarrhythmic therapy has been to modulate cardiac ion channels (sodium, potassium or calcium) or the autonomic nervous system. However, numerous experimental and clinical studies have suggested that cardiac conduction slowing and impaired gap junction intercellular communication (GJIC) are important in the pathogenesis of cardiac arrhythmias, including AF. General conduction slowing or the presence of small islands of intra-atrial conduction block resulting from a decreased gap junction conductance, altered gap junction expression and heterogeneous spatial distribution of gap junctions may provide turning points for the multiple waves, and thereby promote re-entry of impulses. In recognition of this, several authors have proposed gap junction modulation as a potential new target in the treatment of AF. GAP-134 is an antiarrhythmic dipeptide that has demonstrated in vitro and in vivo efficacy in mouse and dog models of arrhythmia. GAP-134 has no apparent proarrhythmic activity or hemodynamic compromise and does not show any significant binding in a panel of >60 different receptors and ion channels. If determined to be safe and effective the indication sought for GAP-134 will be the prevention of post operative atrial fibrillation.