"In the unusual instance when two or more diagnoses equally meet the criteria for principal diagnosis, any one of the diagnoses may be reported as the principal diagnosis when the "

As cell after cell rapidly transmits the electrical charge, the entire heart contracts in one coordinated motion, creating a heartbeat. ... The SA node (called the pacemaker of the heart) sends out an electrical impulse. The upper heart chambers (atria) contract. The AV node sends an impulse into the ventricles.

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