All your organs are autonomous. They rarelly need extra instruction from brains. Heart synapsis are affected by chemicals in energy drinks and treat them as instruction to work harder. Brain detect abnormal heart rate increase and start sending signals to hear to slow down because there is nor reason for wasting energy. Conflicting signals can cause arrhythmia and sever arrhythmia can lead to heart arest. While hear arest is an extreme case, arrhythmia by itself is not something heart should expirience regulary.