"The Pericardium is also called the 'heart protector'... In general theory, the Pericardium is not distinguished from the Heart. It is also the first line of defense against the Heart from External Pathogenic Influences. The Pericardium has a meridian named for it, which reflects the health of the organ. In terms of the Five Elements, these organs are both associated with the fire element. In treatment, it is often best to approach heart problems via the Pericardium, rather than directly. The peak time for the Pericardium is from 7pm to 9pm."

-wikipedia: pericardium