acute coronary syndrome

Acute coronary syndrome is the umbrella term for a coronary artery suddenly going from a slow leak to an emergency. Something — usually a ruptured plaque and a forming clot — abruptly cuts the heart's blood supply, and the situation becomes urgent rather than chronic.

It groups three closely related conditions along a spectrum of severity: unstable angina, NSTEMI and STEMI. They share the same trigger — an unstable plaque with overlying thrombosis — but differ in how completely the artery is blocked and how much muscle is injured. The three are distinguished by symptoms, the ECG (whether the ST segment is elevated), and blood markers of muscle damage (cardiac troponin).

Typical presentation is chest pain at rest or with minimal effort, often more severe or prolonged than previous angina, sometimes with sweating, nausea or breathlessness. Because muscle can be dying minute by minute, acute coronary syndrome is a time-critical emergency: rapid assessment, an ECG and troponin testing guide whether the patient needs urgent reperfusion.

The label is a working diagnosis made before all results are back; it is then refined into unstable angina, NSTEMI or STEMI as the ECG and troponin clarify the picture.