Sinus arrhythmia requires some background information on the heartbeat rhythm. The heartbeat is regulated by a natural pacemaker known as the Sinoatrial (SA) node, situated in the right atrium.

Overall, 907,858 ECGs with normal sinus rhythm (mean age, 62 years; 94% men; 62% white; 11% Black) were acquired from 1987 to 2022 from the 21 regional Veterans Integrated Services Networks within ...