Rate response involves a special sensor, sometimes more than one, to track what you're doing and help your heart keep pace.A heart rhythm typically changes throughout the day. It's slower when you're asleep, for example, and faster when you're exercising or just plain excited, as when you hear an ice cream truck down the block.Some patients have a heart condition or take medicine that keeps the heart from speeding up on its own. This could be problematic, because when the body is excited, it needs more blood circulation. That's why the heart beats faster.That's where the rate-responsive device comes in, to speed up or slow down the heartbeat to meet the body's changing needs for blood. It helps patients stay active and be comfortable by helping their hearts keep up.