Electrical coordination of the atria ventricles is due to

Due to function of sinoatrial node, or SA node.

Explanation:

The SA node is actually only found in your right atrium, but its signal quickly spreads to the left atrium, and this allows both atria to contract at the same time. However, the impulse cannot spread directly to the ventricles. The impulse must be conducted by more of this specialized tissue, namely called the atrioventricular node, or AV node.