When your skin turns pale during a coronary event, such as a heart attack, it is primarily related to circulatory issues rather than respiratory ones.
In such cases, decreased blood flow due to reduced cardiac function can lead to inadequate oxygen delivery to tissues, resulting in paleness (often referred to as pallor). This is due to the body's attempt to prioritize blood flow to vital organs, and the constriction of blood vessels in the skin.
While the respiratory system can play a role in delivering oxygen to the blood, the immediate cause of pallor in this scenario is linked to the circulatory system's inability to adequately supply blood (and therefore oxygen) due to cardiac issues.