bradycardia

Bradycardia (BRAY - dee - CARD - ee - ah) means slowing of the heart rate. This may occur either under nervous system control, as in the gag or diving reflexes that cause the heart to slow, or as a general sign of diminishing blood oxygen concentration, as seen with infantile apnea or in shock.

This is the "B" part of "A's and B's" ("apneas and bradycardias") you might hear around the neonatal intensive care nursery.

Bradycardia is perfectly normal under many circumstances. For example, the heart slows naturally during sleep, or as mentioned above, during immersion under water.