You're confidently incorrect. I'm only vaguely familiar with this topic as my dad had heart surgery last year, and I have a tetraplegic friend who has explained some of it to me. But it only took about five minutes of fudging about on Wikipedia to find a detailed explanation of how the heart generates its own impulses: https://en.wikipedia.org/wiki/Sinoatrial_node?wprov=sfla1

The brain and other systems can influence the rate, but they aren't the primary driver. This is why people get arrhythmia - different systems sending contradictory signals.