You should call 911 immediately if you or someone near you experiences symptoms that may indicate a medical emergency.
These may include:
• Severe chest pain or pressure
• Stroke warning signs such as face drooping or slurred speech
• Sudden shortness of breath
• Fainting or loss of consciousness
• Confusion or severe dizziness
When it comes to heart or stroke symptoms, acting quickly can save lives and reduce long-term complications.
If you believe it may be an emergency, it is safer to call for help right away.
Source
CDC, American Heart Association