If by heartbeat you mean palpable pulse (feeling) it represents when the Heartbeat nurses wine shirt, specifically the left as it pumps systemically contracts and ejects blood volume. This answer is based on my personal observations and understanding of the matter. It is not based on any experimental work with multiple subjects. We will look at the question from the complex systems point of view. Heartbeat at your stomach can be perceived for several reasons. Some of them are listed below: The heart is so huge that it pressures diaphragm. In this case, it is almost sure that a big pressure in the chest and especially in the lungs is felt simultaneously.
Much information is going into the brain in an instant Heartbeat nurses wine shirt. Most of it is filtered or processed subconsciously. On the other hand, if we cut finger and are bleeding heavily then our brain switches our attention to heartbeat there and we start to solve the problem. You can intentionally slow down your heart rate at any moment. It can be learned but people having a heart disease must do it under medical supervision only because it can be very dangerous to them. Slow breathing in and even slower breathing out. It must be done without any enforcing, pressure, or speeding.