Answer:
Persistent chest pain
Explanation:
The life-threatening condition that would require you to immediately summon EMS personnel would be persistent chest pain. Persistent chest pain can be a very dangerous condition, as it can be a symptom of acute coronary syndrome (ACS), myocardial infarction (MI), aortic dissection, pericarditis with tamponade, esophageal perforation, pulmonary embolus and tension pneumothorax. All of these are extremely dangerous conditions that could put the patient at risk of death.
