The Institute of HeartMath has been researching the heart-brain connection for over 18 years and has developed marvelous tools to help us understand the connection and learn to establish and maintain heart coherence. The heart is an electrical organ 40-60 times stronger than the brain and produces an electromagnetic field that radiates 360 degrees around the body to every cell in the body and beyond the skin like radio waves broadcasting into the biosphere.
When the heart feels distressed, or has a strong emotion, the brain immediately receives a signal and the production of stress hormones begins. The coronary arteries constrict and the heart generates an incoherent rhythm. When the heart feels positive emotions, like gratitude, the heart beats in a coherent rhythm and contributes to a greater sense of well-being.
Our emotions are powerful and impact our physical and emotional health. In the following link, the founder of HeartMath describes how to create a state-of-ease. I hope you find it beneficial.