Slow heartbeats indicate bradycardia. Sinus node dysfunction bradycardia is an unusually slow pacemaker. Sinus nodes in the upper chamber atria trigger an impulse for the lower chambers to contract. If the sinus node wears out or fires too slowly, the rate becomes slower.Second and third-degree heart blocks are other afflictions that decrease the beating rates. Second-degree blocks occur when the lower chamber ventricles only receive some of the impulses from the atria. The afflicted may or may not experience symptoms. Third-degree blocks occur when none of the impulses from the atria reach the ventricles, which may cause the heart to beat very slowly.Next
