An irregular heartbeat is called an arrhythmia. A sinus arrhythmia is an irregular heartbeat that’s either too fast or too slow. One type of sinus arrhythmia, called respiratory sinus arrhythmia, is when the heartbeat changes pace when you inhale and exhale. In other words, your heartbeat cycles with your breath. When you breathe in, your heart rate increases. When you exhale, it falls. This condition is benign. It’s a naturally occurring heartbeat variation, and it doesn’t mean you have a serious heart condition. In fact, this condition is common in young, healthy adults and children. A respiratory sinus arrhythmia can occur in older individuals, but in these cases, it’s often associated with heart disease or another heart condition. Sometimes, sinus arrhythmia occurs with another condition called sinus bradycardia. Bradycardia, or a slow heartbeat, is diagnosed when your heart’s natural rhythm is below 60 beats per minute. If the low heart rate produces lengthy pauses between beats, you may have sinus bradycardia with sinus arrhythmia. These pauses can be commonTrusted Source while you sleep.