Disabled Heartbeat but i think it's still working. Is there a plugin or script to check it?

I just disabled Heartbeat with the plugin Heartbeat control and also adding this script in function.php of my child-theme

add_action( 'init', 'stop_heartbeat', 1 );
function stop_heartbeat() {
wp_deregister_script('heartbeat');
}

But i think it's still working and some plugin is overriding it. I still have large cpu spike while the site is in mantainance mode. Is there a function or action that i can use to check if this worked ?