bradycardia-tachycardia syndrome [Gk, bradys + kardia, + tachys, fast, kardia + syn, together, dromos, course] , a disorder characterized by a heart rate that alternates between being abnormally low (less than 60 beats/min) and abnormally high (greater than 100 beats/min). Also called bradytachycardia, tachycardia-bradycardia syndrome. See also sick sinus syndrome, sinus node dysfunction.
