Acute coronary syndromes

High-sensitivity troponin testing is now a standard part of the diagnostic algorithm for cardiac chest pain. Like, standard troponin testing the value peaks at 12 hours after pain onset but value will be rising before this. Interval testing is used in non–STEMI patients to look for a significant change for diagnosis of ACS (or exclusion in low risk patients with normal ECG). It is usually tested at presentation and 3 hours later but varies by hospital and by assay. The definition of ‘significant change’ varies depending on the assay used. A normal value ≥6 hours post-pain onset rules out MI.

The mainstay of the initial medical management of acute coronary syndrome is with morphine analgesia; GTN to aid coronary dilatation and blood flow; aspirin 300mg STAT loading dose followed by 75mg OD; ACS–dose anticoagulation (fondaparinux or unfractionated heparin); and a P2Y12-receptor inhibitor (prasugrel usually now 1^st line, or alternatives ticagrelor or clopidogrel in certain situations). Oxygen should also be given if hypoxaemic. The P2Y12-receptor inhibitor is started during percutaneous coronary intervention (PCI) by the cardiologist. The ACS-dose anticoagulation will be started during PCI in STEMI patients going for immediate PCI, but can be started prior to PCI in NSTEMI patients waiting for PCI.

A stat dose of 300mg aspirin is the correct figure. Low-dose (75mg) aspirin is used for long-term prevention. ACS is the title given to a collection of cardiac diseases that all share the same atherosclerotic aetiology. ST-elevated MI, non-ST-elevated MI and unstable angina are all caused by stenosed coronary arteries starving the myocardium of oxygen (angina), leading to hypoxic cell death (myocardial infarction).

Unstable angina occurs on the cusp of these phenomena, when a rest is no longer adequate to replenish the myocardium with oxygen. Acute coronary stenoses are usually caused by intimal plaque rupture leading to an intraluminal thrombus. Aspirin, a P2Y12-receptor inhibitor and ACS-dose anticoagulation (fondaparinux or unfractionated heparin) aim to prevent platelets binding and therefore to arrest thrombus growth and dissolve the thrombus. Aspirin can cause stomach ulcers and so, in order to balance risks and benefits, low-dose aspirin is given long term; a higher dose (300 mg) is given acutely.

Statins prophylactically lower serum cholesterol, and so it is thought to reduce plaque formation in the first place. ACE inhibitors reduce myocardial remodelling and beta-blockers reduce afterload and heart rate, so the heart does not have to work as hard – this lowers its oxygen demand, hopefully enough to prevent hypoxic damage.

Further information:

RCEM: Acute coronary syndromes 

A stat dose of 300 mg aspirin is the correct figure. Low-dose (75 mg) aspirin is used for long-term prevention. ACS is the title given to a collection of cardiac diseases that all share the same atherosclerotic aetiology.

ST-elevated MI (STEMI), non-ST-elevated MI (NSTEMI) and unstable angina are all caused by stenosed coronary arteries starving the myocardium of oxygen (angina), leading to hypoxic cell death (myocardial infarction). Unstable angina occurs on the cusp of these phenomena, when a rest is no longer adequate to replenish the myocardium with oxygen. Acute coronary stenoses are usually caused by intimal plaque rupture leading to an intraluminal thrombus.

Aspirin, a P2Y12-receptor inhibitor and ACS–dose anticoagulation (fondaparinux or unfractionated heparin) aim to prevent platelets binding and therefore to arrest thrombus growth and dissolve the thrombus. Aspirin can cause stomach ulcers and so, in order to balance risks and benefits, low-dose aspirin is given long term; a higher dose (300 mg) is given acutely. Statins prophylactically lower serum cholesterol, and so it is thought to reduce plaque formation in the first place.

ACE inhibitors reduce myocardial remodelling and beta-blockers reduce afterload and heart rate, so the heart does not have to work as hard – this lowers its oxygen demand, hopefully enough to prevent hypoxic damage.

Further information:

https://www.nice.org.uk/guidance/ng185/chapter/Recommendations