Source:http://linkedlifedata.com/resource/umls/id/C0428908
NCI: A derangement in the normal functioning of the sinoatrial node. Typically, SA node dysfunction is manifest as sinoatrial exit block or sinus arrest, but may present as an absolute or relative bradycardia in the presence of a stressor. It may be associated with bradycardia-tachycardia syndrome,NCI: A derangement in the normal functioning of the sinoatrial node. Typically, SA node dysfunction is manifest as sinoatrial exit block or sinus arrest, but may present as an absolute or relative bradycardia in the presence of a stressor. It may be associated with bradycardia-tachycardia syndrome. (NCI)