#acute-coronary-syndrome #STEMI #NSTE-ACS #antiplatelet-therapy #revascularization #cardiogenic-shock #secondary-prevention #guidelines

ACS Management

Definition

This page covers the management of acute coronary syndrome from first medical contact to discharge and long-term secondary prevention: prehospital triage, diagnosis and risk stratification, antithrombotic and lipid therapy, reperfusion, invasive strategy, mechanical complications, cardiogenic shock, and the transition to chronic coronary disease. The clinical recommendations derive predominantly from the 2025 ACC/AHA ACS guideline (sources/ACS-AHA-2025, rating: very high)

Defining and classifying MI — the Fifth Universal Definition taxonomy, the retained STEMI/NSTEMI axis, and the rival OMI/NOMI framework — is on entities/Acute-Coronary-Syndrome. The split matters to management because the two classification frameworks disagree about who should go to the catheter laboratory emergently, which is why this page closes with ### When the ECG Axis Fails.

Key Concepts

Prehospital Assessment

12-lead ECG acquisition and interpretation within 10 minutes of first medical contact — Class I/B-NR. (sources/ACS-AHA-2025, rating: very high)
STEMI: direct EMS transport to a PCI-capable hospital; FMC-to-device goal ≤90 min, acceptable ≤120 min where 90 min is not achievable.
Prehospital cath lab activation and advance notification significantly reduce reperfusion time and short- and long-term mortality.

Diagnosis

hs-cTn preferred over conventional cTn; serial sampling at 0 and 1–2 h (hs-cTn) or 0 and 3–6 h (conventional); a rising/falling pattern plus ≥1 value above the 99th percentile defines AMI. (sources/ACS-AHA-2025, rating: very high)
Evidence-based clinical decision pathways incorporating delta hs-cTn achieve NPV >99.5% and reduce unnecessary testing in 21%–43% of patients.
Risk scores: GRACE 2.0 — superior to physician assessment for predicting death or MI in both STEMI and NSTE-ACS — and the TIMI Risk Score are validated for stratification and for timing of the invasive strategy.

Antiplatelet Therapy

Aspirin: loading dose 162–325 mg → maintenance 75–100 mg daily — Class I/A. Non-enteric-coated and chewed for faster onset. (sources/ACS-AHA-2025, rating: very high)
P2Y12 inhibitors: ticagrelor (180 mg load → 90 mg twice daily) or prasugrel (60 mg load → 10 mg daily) preferred over clopidogrel for PCI — Class I/B-R. Clopidogrel (300–600 mg load → 75 mg daily) is an appropriate alternative — Class I.
Prasugrel is contraindicated with prior stroke or TIA — Class III: Harm. Ticagrelor causes transient dyspnoea in 10%–15% and should always be given with aspirin ≤100 mg daily.

Anticoagulation

UFH is standard. Bivalirudin is COR 1 for STEMI-PCI — BRIGHT-4 showed a post-PCI full-dose infusion for 2–4 h reduced death plus bleeding versus UFH. (sources/ACS-AHA-2025, rating: very high)
Fondaparinux must not be used alone to support PCI — catheter thrombosis risk.

Lipid Management

High-intensity statin — Class I/A. (sources/ACS-AHA-2025, rating: very high)
Add a nonstatin agent (ezetimibe, PCSK9 inhibitor, inclisiran, bempedoic acid) if LDL-C ≥70 mg/dL on maximal statin — Class I/A; reasonable if LDL-C 55–69 mg/dL — Class IIa.
Fasting lipid panel 4–8 weeks after initiation or adjustment of lipid-lowering therapy — Class I/C-LD.
See concepts/Dyslipidemia-Management.

Oxygen

Supplemental oxygen only if SpO₂ <90%. Routine oxygen at SpO₂ ≥90% is not recommended — Class III: No Benefit/A (DETO2X-AMI, AVOID). (sources/ACS-AHA-2025, rating: very high)

Reperfusion — STEMI

Primary PCI preferred over fibrinolysis; radial approach preferred over femoral — reduces bleeding (51% RRR), vascular complications (62%) and all-cause death (24%). (sources/ACS-AHA-2025, rating: very high)
FMC-to-device ≤90 min as the system goal; each 30-minute delay carries a 7.5% relative increase in 1-year mortality.
Where PCI is not available within the time window, give fibrinolysis and transfer to a PCI centre for angiography within 3–24 h after lysis.

Invasive Strategy — NSTE-ACS

Intermediate/high risk: routine invasive approach with intent to revascularise during the index hospitalisation — Class I/A (18% reduction in death/MI and 25% reduction in MI versus a selective invasive strategy in a collaborative meta-analysis). (sources/ACS-AHA-2025, rating: very high)
Immediate invasive (<2 h): refractory angina, haemodynamic or electrical instability — Class I/C-LD.
Low risk: routine or selective invasive approach with noninvasive testing (stress testing or CCTA) before discharge — Class I/A.
Comatose, stable, no ST-elevation after cardiac arrest: immediate angiography is not recommended — Class III: No Benefit/A, across 6 contemporary RCTs.
Elderly NSTEMI (≥75 years) — SENIOR-RITA (NEJM 2024; n=1,518; mean age 82; 32% frail; median 4.1 years): invasive strategy (angiography ± revascularisation) versus conservative was neutral on the primary composite of CV death or nonfatal MI (25.6% vs 26.3%; HR 0.94; P=0.53). Nonfatal MI was reduced (HR 0.75; P<0.05) but offset by numerically more CV deaths (HR 1.11); an early benefit at 1 year (12.8% vs 16.8%) had eroded by 5 years (35.4% vs 34.8%). Radial access was used in 89.3%, procedural complications were <1%, and subsequent revascularisation fell sharply (3.9% vs 13.7%). See concepts/NSTEMI-Elderly-Invasive-Strategy for the full synthesis including After Eighty and the Kotanidis meta-analysis. (sources/PCI-Elderly-SENIORRITA-NEJM-2024, rating: very high)

Multivessel Disease

Complete revascularisation in STEMI: recommended — Class I/A; single-procedure multivessel PCI may be preferred over staged — Class IIb/B-R (BIOVASC, MULTISTARS AMI). (sources/ACS-AHA-2025, rating: very high)
MULTISTARS AMI (NEJM 2023; n=840; haemodynamically stable STEMI with multivessel disease): immediate multivessel PCI was superior to staged PCI at 1 year (8.5% vs 16.3%; RR 0.52; P<0.001 for both noninferiority and superiority), driven by fewer nonfatal MIs (2.0% vs 5.3%) and unplanned revascularisations (4.1% vs 9.3%) in the first 45 days. Death, stroke and HF hospitalisation were similar. It does not apply to cardiogenic shock, left main disease or CTO. See concepts/Multivessel-PCI-STEMI-Timing. (sources/complete-pci-multistars-ami-nejm-2023, rating: high)
STEMI with cardiogenic shock: culprit-only PCI; routine non-culprit PCI is not recommended — Class III: Harm/B-R (CULPRIT-SHOCK: higher 30-day death or renal replacement therapy with multivessel PCI).
NSTE-ACS with multivessel disease: complete revascularisation — Class I/B-R (FIRE in the elderly; BIOVASC). CABG is preferred for complex left main or LAD disease, and for diabetes with multivessel LAD involvement.
See concepts/Complete-Revascularization.

Cardiogenic Shock

Emergency culprit-vessel revascularisation (PCI or CABG) regardless of time from onset — Class I/B-R. (sources/ACS-AHA-2025, rating: very high)
Microaxial flow pump (Impella): Class IIa/B-R for selected STEMI with severe or refractory cardiogenic shock — DanGer-SHOCK (26% mortality reduction at 180 days; HR 0.74; NNT 8). Selection: SCAI Stage C/D/E, non-comatose, LVEF <45%, adequate peripheral vasculature.
IABP and VA-ECMO: routine use not recommended — Class III: No Benefit/B-R (IABP-SHOCK II; ECLS-SHOCK; ECMO-CS).
See entities/Heart-Failure for cardiogenic shock haemodynamics and concepts/Right-Heart-Catheterization for assessment.

Post-ACS Complications

Mechanical complications (ventricular septal rupture, papillary muscle rupture, free wall rupture): manage at a surgical centre, with mechanical circulatory support as a bridge; definitive surgical repair is preferred, with percutaneous options reserved for prohibitive surgical risk. (sources/ACS-AHA-2025, rating: very high)
ICD: LVEF ≤40% at ≥40 days post-MI and ≥90 days post-revascularisation — Class I/A; clinically relevant ventricular arrhythmia >48 h within 40 days — Class IIa/C-EO; wearable cardioverter-defibrillator (VEST) — Class IIb/B-R, having missed its primary endpoint.
Post-MI pericarditis: high-dose aspirin plus colchicine; glucocorticoids are potentially harmful through impaired myocardial healing.
LV thrombus: anticoagulation for 3 months; DOACs non-inferior to VKA; highest risk with anterior STEMI and LVEF <30%.

Secondary Prevention at Discharge

DAPT default: aspirin plus an oral P2Y12 inhibitor for ≥12 months where bleeding risk is not high — Class I/A. See concepts/DAPT-Strategies for de-escalation. (sources/ACS-AHA-2025, rating: very high)
ACS with an oral anticoagulant: discontinue aspirin 1–4 weeks post-PCI and continue P2Y12 (preferably clopidogrel) plus the OAC — Class I/B-R. See entities/Atrial-Fibrillation.
Colchicine 0.5 mg daily: Class IIb/B-R — COLCOT (23% composite MACE reduction at 22 months), contradicted by CLEAR (below). See concepts/Colchicine-in-Cardiovascular-Disease.
Influenza vaccination: annual — Class I/A (IAMI trial reduced CV death, MI and stent thrombosis versus placebo).
Cardiac rehabilitation: referral before discharge — Class I/A; home-based CR is equivalent for quality of life and safety. ESC 2026 gives post-ACS/CCS rehabilitation a Class I/A recommendation and sets 24 sessions over 12 weeks as the standard minimum. See concepts/Cardiac-Rehabilitation. (sources/ACS-AHA-2025, rating: very high; sources/CRP-ESC-2026, rating: very high)
Multidomain rehabilitation in elderly or frail post-MI patients: PIpELINe (NEJM 2025; n=512; median age 80; SPPB 4–9) — a 12-month multidomain intervention combining cardiovascular risk factor management, dietary counselling and exercise training reduced CV death or unplanned CV hospitalisation at 1 year (HR 0.57; P=0.01; NNT ≈12.5), with HF hospitalisation sharply reduced (HR 0.20). Standard CR programmes have limited reach in this population; tailored multidomain models are an evidence-based alternative. See entities/Frailty-in-Cardiovascular-Disease. (sources/pipeline-mi-nejm-2025, rating: very high)
LVEF assessment before discharge — Class I/C-LD; repeat at 6–12 weeks if reduced.

Transition to Chronic Coronary Disease

Once the patient is stabilised and discharged, management passes to the chronic phase governed by the 2023 AHA/ACC chronic coronary disease guideline. (sources/CCS-AHA-2023, rating: very high)
Key chronic-phase questions not covered by the ACS guideline: beta-blocker de-escalation (now supported by SMART-DECISION where LVEF ≥40% and the patient is stable ≥1 year), extended DAPT versus low-dose rivaroxaban, INOCA where anatomy is non-obstructive, CABG for ischaemic cardiomyopathy, and SGLT2 inhibitor / GLP-1 receptor agonist integration.
See entities/Chronic-Coronary-Disease.

When the ECG Axis Fails

The classification debate on entities/Acute-Coronary-Syndrome has a direct operational consequence here, because the entire pathway above is gated on ST-elevation.

25%–34% of patients managed as NSTEMI have TIMI-0/1 flow at angiography and nearly twice the mortality of NSTEMI with TIMI ≥2 — yet under the STEMI-gated pathway they are not activated for emergent reperfusion. (sources/failure-stemi-criteria-lad-omi-ehjacc-2025, rating: high)
38% of total LAD occlusions never met STEMI criteria on any serial pre-angiography ECG, and reached the laboratory with a median door-to-balloon time of 97 vs 40 minutes — with equivalent infarct size, so the delay bought nothing.
The protocol cannot be fixed by protocol alone. The 2022 ACC and 2024 SCAI documents acknowledge the sensitivity gap but give no actionable quantitative criteria; the HATW score is the first validated candidate. Until an OMI-based activation strategy is tested prospectively, this page's recommendations remain STEMI-gated.

Evidence Anchors

Trial detail for the three drug classes with dedicated pages lives there, not here.

Beta-blockers — LVEF <40% or HF: Class I indefinitely (metoprolol succinate, carvedilol, bisoprolol). LVEF ≥40%, no HF, stable ≥1 year: SMART-DECISION (NEJM 2026; n=2,540) shows discontinuation is noninferior to continuation (HR 0.80; upper CI 1.13 below the NI margin of 1.4). LVEF ≥50% without another indication: initiation or continuation not supported — IPD meta-analysis (NEJM 2026; n=17,801; HR 0.97; P=0.54). Atrial fibrillation was excluded from SMART-DECISION and rate control often justifies continuation. Full synthesis including REDUCE-AMI, REBOOT, BETAMI and ABYSS: concepts/Beta-Blocker-Post-MI. (sources/BB-SMARTDECISION-NEJM-2026, rating: very high; sources/bb-mi-nejm-2026)
Mineralocorticoid receptor antagonists — eplerenone is Class I/A post-MI with LVEF <40% plus HF or diabetes (EPHESUS; n=6,642; 15% RRR for all-cause mortality). CLEAR (NEJM 2025; n=7,062; 95.1% STEMI) tested spironolactone 25 mg in unselected AMI post-PCI and was negative on both primary endpoints (CV death or new/worsening HF, HR 0.91; MACE, HR 0.96). Gynecomastia 2.3% vs 0.5%; hyperkalaemia 1.1% vs 0.6%. Full synthesis including RALES and ALBATROSS: concepts/Mineralocorticoid-Receptor-Antagonists-Post-MI. (sources/spironolactone-ami-clear-nejm-2025, rating: very high)
SGLT2 inhibitors — EMPACT-MI (NEJM 2024; n=6,522) gave empagliflozin within 14 days of MI to a high-risk enriched population and was neutral on HF hospitalisation or all-cause death (8.2% vs 9.1%; HR 0.90; P=0.21). HF hospitalisation alone was reduced (HR 0.77) and total HF hospitalisations markedly so (148 vs 207; rate ratio 0.67); death was unchanged. Benefit is context-dependent: established in established HF, not in acute post-MI prevention. Mechanistic detail: concepts/SGLT2-Inhibitors-in-CKD. (sources/empagliflozin-empactmi-nejm-2024, rating: very high)

Hong Kong Protocol — Doses and Thresholds

The Hong Kong Hospital Authority handbook supplies the operational version of the same pathway, useful where the guideline pages stop at a recommendation. (sources/Handbook-HA-2024, rating: high)

Antithrombotic loading: aspirin 160–320 mg then 80–100 mg daily; clopidogrel 300–600 mg or ticagrelor 180 mg; enoxaparin 1 mg/kg q12h, or weight-banded nadroparin. After fibrinolysis, clopidogrel loading is 300 mg for age ≤75 and is omitted entirely above 75.
Fibrinolysis where primary PCI is not available within 12 hours: tenecteplase 30 mg (<60 kg) rising to 50 mg (≥90 kg), halved for age ≥75; alteplase 15 mg bolus, then 0.75 mg/kg over 30 min, then 0.5 mg/kg over 1 h.
ST-elevation thresholds by age and sex: ≥2.5 mm in men <40, ≥2 mm in men ≥40, ≥1.5 mm in women, in V2–V3; ≥1 mm in all other leads.
Failed reperfusion is <50% resolution of the ST-elevation in the worst lead at 60–90 minutes, corroborated by pain resolution, an early CPK peak and accelerated idioventricular or nodal rhythm — the trigger for rescue PCI.
Secondary prevention at LVEF ≤40% with diabetes or heart failure adds an aldosterone blocker; ARNI is started 36 hours after stopping ACE-I; an SGLT2 inhibitor is considered for coexisting heart failure.

Contradictions / Open Questions

The handbook is organised entirely around STEMI/NSTEMI, which the overview page's own OMI section argues is the wrong frame. Its reperfusion decision hinges on ST-elevation, its fibrinolysis thresholds are calibrated to it, and nothing in the protocol addresses occlusion MI without ST-elevation. This page therefore holds both the operational pathway and the argument that the pathway's central distinction is inadequate, without reconciling them. (sources/Handbook-HA-2024, rating: high)
STEMI criteria versus OMI — the paradigm gap. Standard STE criteria miss 38% of total LAD occlusions on all serial ECGs yet remain the primary gatekeeper for cath lab activation, and NSTEMI patients with TIMI-0/1 flow have nearly twice the mortality of NSTEMI with open arteries. Expert ECG interpretation and AI both achieve 100% sensitivity where STEMI criteria fail, but implementation requires validated quantitative criteria and prospective outcome data for OMI-based activation. (sources/failure-stemi-criteria-lad-omi-ehjacc-2025, rating: high)
Ticagrelor versus aspirin monotherapy after the DAPT phase. Prasugrel monotherapy safety is not established post-ACS, and aspirin monotherapy after P2Y12 discontinuation carries excess thrombotic risk in the STEMI subgroup. The optimal single antiplatelet after DAPT remains debated. (sources/ACS-AHA-2025, rating: very high)
Routine pre-loading of P2Y12 inhibitors in NSTE-ACS. No RCT benefit for ticagrelor pre-loading before an early (<24 h) invasive strategy, and prasugrel pre-loading increases bleeding without ischaemic benefit — yet pharmacodynamic delay in STEMI supports earlier loading. The optimal timing remains an evidence gap.
CLEAR null result versus COLCOT benefit — colchicine in acute MI unresolved. CLEAR (NEJM 2025; n=7,062; largest AMI colchicine RCT; 649 events; HR 0.99; P=0.93) directly contradicts COLCOT (n=4,745; HR 0.77; P=0.02). Both enrolled post-MI patients at 0.5 mg/day; CLEAR was larger, had more events and longer follow-up. Possible explanations include more intensive contemporary background therapy, a 95% STEMI population, and mid-trial protocol changes. CLEAR joins CHANCE-3 and CONVINCE as three recent neutral colchicine trials, more recent than COLCOT and LoDoCo2. ESC Class IIa and FDA approval require re-evaluation. The COPS non-cardiovascular death signal (8 vs 1) also reversed direction in CLEAR, with numerically fewer non-cardiovascular deaths on colchicine — unlikely to represent a true risk. See concepts/Colchicine-in-Cardiovascular-Disease. (sources/colchicine-ami-clear-nejm-2025, rating: very high)
Microaxial flow pump generalisability. DanGer-SHOCK ran at 14 specialised European centres with strict selection; optimal insertion timing, duration and weaning are undefined, and real-world limb ischaemia and bleeding rates may be higher. (sources/ACS-AHA-2025, rating: very high)
Beta-blocker evidence in NSTE-ACS and at preserved ejection fraction. Support for routine beta-blockade in NSTE-ACS specifically (as opposed to HFrEF post-ACS) is limited. At LVEF ≥50% without another indication the IPD meta-analysis is now conclusive against benefit, leaving the LVEF 40–49% band and NSTE-ACS patients without a direct answer. See concepts/Beta-Blocker-Post-MI.
Beta-blocker discontinuation timing. SMART-DECISION establishes noninferiority at a median 4.7 years post-MI; safe discontinuation earlier, the LVEF 40–49% subgroup, women (only 12.8% enrolled) and generalisability outside Korea all remain open. (sources/BB-SMARTDECISION-NEJM-2026, rating: very high)
Invasive strategy in elderly NSTEMI — SENIOR-RITA versus After Eighty. SENIOR-RITA (n=1,518; 4.1-year follow-up; neutral primary HR 0.94) contradicts After Eighty (n=457; 18-month follow-up; positive for invasive strategy). Era effects, longer follow-up revealing curve convergence, improved background GDMT and the 50% non-revascularisation rate in the invasive arm all contribute. Current guidelines cannot make a universal recommendation; shared decision-making informed by frailty, comorbidity, anatomical suitability and patient preference is recommended. (sources/PCI-Elderly-SENIORRITA-NEJM-2024, rating: very high)
MRA benefit post-MI is EF-dependent, and CLEAR did not collect LVEF. EPHESUS showed eplerenone benefit at EF <40%; CLEAR tested spironolactone in all comers without LVEF data, so the apparent EF-specific effect cannot be verified. The on-treatment analysis shows HR 0.79 and 0.83 approaching significance against a clearly negative ITT (HR 0.91/0.96), with a 28% vs 24% discontinuation differential that probably diluted the ITT effect — whether a better-tolerated MRA in a lower-dropout trial would show benefit is unanswered. (sources/spironolactone-ami-clear-nejm-2025, rating: very high)
SGLT2 inhibitors are context-dependent — established HF versus post-MI prevention. EMPACT-MI is null for the composite despite proven benefit in established HFrEF (EMPEROR-Reduced HR 0.75) and HFpEF (EMPEROR-Preserved HR 0.79). The HF hospitalisation component alone was reduced but death — driven by stent thrombosis, arrhythmias and mechanical complications — was not. Partially stunned, reversible myocardium in a 90%-revascularised STEMI population, combined with non-HF-modifiable deaths, explains the null result. (sources/empagliflozin-empactmi-nejm-2024, rating: very high)
Transition from ACS to chronic coronary syndrome. The exact timing is undefined, and the management implications for de-escalating antithrombotic therapy are individualised and lack RCT data. (sources/ACS-AHA-2025, rating: very high)

Connections

The syndrome and its classification: entities/Acute-Coronary-Syndrome — the parent overview
Chronic phase: entities/Chronic-Coronary-Disease — where management goes after discharge
Antithrombotic strategy: concepts/DAPT-Strategies · concepts/AF-Stable-CAD-Antithrombotic
Reperfusion and revascularisation: concepts/Multivessel-PCI-STEMI-Timing · concepts/Complete-Revascularization · concepts/Intracoronary-Imaging-Guided-PCI
Drug classes with dedicated pages: concepts/Beta-Blocker-Post-MI · concepts/Mineralocorticoid-Receptor-Antagonists-Post-MI · concepts/SGLT2-Inhibitors-in-CKD · concepts/Colchicine-in-Cardiovascular-Disease · concepts/Dyslipidemia-Management
Special populations: concepts/NSTEMI-Elderly-Invasive-Strategy · entities/Frailty-in-Cardiovascular-Disease · entities/Atrial-Fibrillation
Rehabilitation: concepts/Cardiac-Rehabilitation
Haemodynamics and shock: entities/Heart-Failure · concepts/Right-Heart-Catheterization
Resuscitation: concepts/Cardiopulmonary-Resuscitation