We introduce a simple method to distinguish permanent from transient non-sinus rhythm immediately after resuscitation in cardiac operations. An ice slush of normal saline is sprayed on the surface of the right atrium around the sinus node. If the arrhythmia is transient, the heart usually regains sinus rhythm; if not, the arrhythmia will most likely be permanent. Although we do not know the mechanism, this technique is easy and has worked well in 162 patients.