Heart coherence is when your brain waves and the waves of your heart are synchronized and moving together in an organized manner. When you're in a state of coherence, not only are your heart and mind in alignment, but your cardiovascular system, immune system, hormones, and nervous system are all working together in a harmonious and efficient manner.

https://www.heartmath.org/resources/heartmath-tools/quick-coherence-technique-for-adults/