Is it possible to control the heart beat

Nor voluntarily, the way we can control rate and depth of breathing (for a while). We can, however, varyheart rate, ie by engaging in strenuous physical activity or emotional stress, resting, sleeping, etc. The variations are not under voluntary control , but by the autonomic nervous system. 

Also, like someone stated, drugs like beta blockers are used to control arrhythmias hence they can control heart rate