To control cardiac arrhythmias such as atrial fibrillation post-operatively, a synthetic resorbable self-curing hydrogel material may be introduced as a non-ablative agent into one or more cardiac fat pads in proximity to the autonomic ganglia therein. Any desired technique may be used for introducing the agent, including injection. The sinoatrial nodal fat pad target site and the atrioventricular nodal fat pad target site are identified using a stimulator, which may have electrodes coupled thereto or which may be coupled to electrodes built into a delivery system.