Cardiovascular

Non-ST-Elevation Myocardial Infarction (NSTEMI)

Plaque rupture or erosion infarcts myocardium without producing persistent ST elevation, so the ECG cannot time treatment and a mortality risk score does it instead.

In a nutshell

Non-ST-elevation myocardial infarction (NSTEMI) is acute coronary syndrome (ACS) with a troponin rise and evidence of ischaemia but no persistent ST elevation. Give aspirin 300 mg and an antithrombin, then let a risk score and clinical stability decide how fast the angiogram happens.

Classic presentation

A 68-year-old with 40 minutes of crushing chest pain at rest, ST depression in the lateral leads, and a high-sensitivity troponin that rises on the repeat sample.

Key points

GRACE (Global Registry of Acute Cardiac Events) predicts 6-month mortality. NICE names it as only one example of an acceptable score. It does not choose the antiplatelet.
The 3.0% cut-off sits inside the intermediate band, so intermediate or higher risk and predicted 6-month mortality above 3.0% describe the same group.
Troponin cut-offs are published per assay and differ by sex. The Roche Elecsys troponin T assay uses 14 nanograms per litre overall, 9 for women and 16.8 for men.
Older non-high-sensitivity troponin is at its most sensitive 10 to 12 hours after symptom onset. High-sensitivity assays exist to shorten that wait.
Assess left ventricular function in everyone after NSTEMI. In unstable angina NICE only says consider it, and that deliberate difference is examined.
Prasugrel is withheld until the coronary anatomy is known and percutaneous coronary intervention (PCI) is intended. Ticagrelor is not. If an oral anticoagulant continues, use clopidogrel.
Unstable angina runs the same NICE pathway without the troponin rise, and does not automatically inherit the post-MI secondary-prevention bundle.

First-line investigation

A 12-lead ECG as soon as possible, then high-sensitivity troponin: NSTEMI needs a rise and/or fall above the assay's 99th-percentile upper reference limit plus evidence of ischaemia.

Management

First contact, before the diagnosis

ABCDE (airway, breathing, circulation, disability, exposure), IV access, rhythm and saturation monitoring, and a 12-lead ECG as soon as possible. A normal ECG does not exclude ACS.²
Aspirin 300 mg by mouth, chewed or dispersed in water, as a single loading dose, unless clearly allergic.^1,6
Oxygen only if oxygen saturation (SpO2) is below 94%: target 94% to 98%, or 88% to 92% if at risk of hypercapnic respiratory failure.²
Pain: glyceryl trinitrate (GTN) 1 to 2 sublingual sprays of 400 micrograms, repeated at 5 minutes, maximum 3 doses. Do not use the response to diagnose.^2,7
Then morphine 5 to 10 mg by slow IV injection at 1 to 2 mg/minute, or 2.5 to 5 mg if frail or elderly.^2,8

Once unstable angina or NSTEMI is diagnosed

Confirm a troponin rise and/or fall above the assay's 99th-percentile limit plus evidence of ischaemia. A raised troponin alone is myocardial injury, not NSTEMI.^2,4,3
Fondaparinux 2.5 mg subcutaneously once daily, for up to 8 days or until discharge, unless bleeding risk is high or immediate angiography is planned.^1,9
Creatinine above 265 micromoles per litre: unfractionated heparin instead. 5000 units IV, or 75 units/kg, then 18 units/kg/hour, adjusted by clotting monitoring.^1,10
Reconsider the choice and dose of any antithrombin in advancing age, low body weight, renal impairment or known bleeding complications.¹

GRACE: what it predicts, what it decides

GRACE predicts 6-month mortality after unstable angina or NSTEMI. It decides one thing: whether and how fast you do coronary angiography. It is not a diagnosis.¹
Score it once aspirin and an antithrombin have been given. Inputs: age, previous MI, previous revascularisation, blood pressure, heart rate, ECG, troponin, creatinine, glucose and haemoglobin.¹
Bands: 1.5% or below lowest; above 1.5% to 3.0% low; above 3.0% to 6.0% intermediate; above 6.0% to 9.0% high; over 9.0% highest.¹
Above 3.0%, meaning intermediate or higher: consider coronary angiography, with follow-on PCI if indicated, within 72 hours of first admission.¹
3.0% or less: consider conservative management without early angiography, with ischaemia testing before discharge and angiography if ischaemia recurs or is demonstrated.¹
Clinically unstable at any score: immediate coronary angiography. NICE attaches no number of hours to immediate, so it means now, not tomorrow's list.¹
A young person with a low 6-month mortality score can still be at high risk of events and may benefit from early angiography.¹

The second antiplatelet, tied to the strategy

Having angiography, no anticoagulation indication: ticagrelor 180 mg then 90 mg twice daily with aspirin, usually up to 12 months.^1,12
Or prasugrel 60 mg then 10 mg once daily, 5 mg if under 60 kg or aged 75 and over, given only once anatomy is defined and PCI intended.^1,11
Already on an oral anticoagulant: clopidogrel 300 mg then 75 mg once daily with aspirin. Do not routinely combine prasugrel or ticagrelor with an anticoagulant.^1,13
PCI not indicated: ticagrelor with aspirin, or clopidogrel with aspirin or aspirin alone if bleeding risk is high.¹
Having PCI: give systemic unfractionated heparin in the catheter laboratory whether or not fondaparinux was given. In November 2020 this was off-label.^1,10
Choose PCI, coronary artery bypass grafting (CABG) or medical treatment from the anatomy, comorbidity and the person's wishes, with a cardiologist and cardiac surgeon if unclear.¹

Type 2 myocardial infarction: the exit door

Type 2 MI is infarction from an oxygen supply-and-demand mismatch, not acute plaque thrombosis: anaemia, tachyarrhythmia, hypoxaemia, sepsis, hypotension, severe hypertension.^3,2
Treat the precipitant. Fondaparinux, dual antiplatelet therapy (DAPT) and 72-hour angiography follow a diagnosis of unstable angina or NSTEMI, not a moving troponin.¹
A raised troponin without evidence of acute ischaemia is myocardial injury. Reassess for myocarditis, aortic dissection and pulmonary embolism before confirming ACS.^2,3

Before discharge, after a type 1 NSTEMI

Aspirin 75 mg once daily indefinitely, and continue DAPT for up to 12 months after an MI unless bleeding, anticoagulation or surgery changes that.^1,6
Atorvastatin 80 mg once daily, started without delay. Target LDL cholesterol 2.0 mmol/litre or less, or non-HDL cholesterol 2.6 mmol/litre or less.^5,14,15
Ramipril, an angiotensin-converting enzyme (ACE) inhibitor, 2.5 mg once daily once stable, titrated towards 10 mg daily at 12 to 24 hour intervals. Continue indefinitely.^1,16
Bisoprolol once stable: 5 mg once daily, or 1.25 mg once daily titrated stepwise if left ventricular ejection fraction (LVEF) is reduced. Reduced LVEF: continue indefinitely.^1,17
Heart failure with reduced LVEF: add an aldosterone antagonist licensed for post-MI use within 3 to 14 days, after the ACE inhibitor, monitoring potassium and renal function.¹
Assess left ventricular function in everyone who has had an NSTEMI, and begin cardiac rehabilitation before discharge, with the first session within 10 days of discharge.¹
Recheck the full lipid profile and liver transaminases 2 to 3 months after starting or changing lipid-lowering treatment, and transaminases again at 12 months.⁵

Exam traps

A troponin rise is not NSTEMI. Without evidence of acute ischaemia it is myocardial injury, and the treatment is the cause, not the ACS bundle.
Do not give a second antiplatelet for undifferentiated chest pain. NICE says not before unstable angina or NSTEMI has been diagnosed.
Ticagrelor's acute maintenance dose is 90 mg twice daily. The 60 mg twice daily dose is the extended one, used after the first 12 months.
Fibrinolysis has no place in NSTEMI: no benefit and real bleeding harm. That is a treatment fact, not proof the artery is only partly occluded.
The 72 hours runs from first admission, not from the troponin result and not from the moment the risk score was calculated.
Oxygen is not treatment for chest pain. Only below 94% saturation, and NG185 contains no oxygen recommendation at all: the source is CG95.
Having had fondaparinux does not exempt anyone from unfractionated heparin in the catheter laboratory. NICE says give it whether or not fondaparinux was given.
A normal ECG or absent ST elevation never proves the artery is open. Posterior and circumflex occlusions hide from the standard 12 leads.

Illustrations

Wellens pattern: high-risk anterior ischaemiaTwelve-lead ECG showing a Wellens T-wave pattern, which warns of critical proximal left anterior descending coronary disease and needs urgent specialist assessment. It is a high-risk non-ST-elevation acute coronary syndrome pattern, not a generic diagnostic tracing for NSTEMI.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0

Illustrative troponin rise-and-fall curveAn illustrative concentration-time curve after myocardial injury, showing the rise and fall that the diagnosis depends on. The shape is generic: absolute values and thresholds are published for each assay, and a rise alone is not NSTEMI without evidence of acute ischaemia.PassFinals · original

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.