Wednesday, September 16, 2026

Management of Myocardial Infarction

Management of Myocardial Infarction

Clinical Management of Myocardial Infarction: High-Yield Lecture Notes

Source and Scope

  • Primary source: Landi A, Malik FTN, Chieffo A, Valgimigli M. Clinical Management of Myocardial Infarction. Circulation. 2026;154(11):1036-1051.
  • Online publication: September 14, 2026. Issue publication: September 15, 2026.
  • DOI: https://doi.org/10.1161/CIRCULATIONAHA.126.079317
  • Scope: Diagnosis, risk stratification, acute reperfusion, antithrombotic treatment, revascularization, cardiogenic shock, secondary prevention, and myocardial infarction with nonobstructive coronary arteries (MINOCA).
  • The review is a state-of-the-art synthesis, not a clinical practice guideline. Recommendations should be reconciled with current guidelines, local protocols, contraindications, and patient-specific ischemic and bleeding risks.

Important 2026 Terminology Update

  • The review describes the Fourth Universal Definition of Myocardial Infarction and its numeric types 1 through 5.
  • The Fifth Universal Definition of Myocardial Infarction was published in August 2026 and replaced the numeric system with 3 clinical categories:
    • Primary myocardial infarction: A spontaneous presentation caused by an acute coronary process, including atherothrombosis, spontaneous coronary artery dissection, embolism, vasospasm, or late stent or graft failure.
    • Secondary myocardial infarction: Acute ischemic myocardial injury caused by oxygen supply-demand imbalance from another acute condition.
    • Procedure-related myocardial infarction: Myocardial infarction occurring as a complication of a percutaneous or surgical cardiac procedure.
  • The older type 1, type 2, type 3, type 4, and type 5 labels remain common in prior literature and clinical communication, but learners should recognize that the current universal definition uses the newer clinical classification.

Core Clinical Takeaway

  • Modern myocardial infarction care follows a sequence:
    • Recognize ischemia rapidly and obtain an electrocardiogram (ECG).
    • Identify patients who require immediate reperfusion without waiting for biomarker confirmation.
    • Confirm acute myocardial injury with serial cardiac troponin and determine whether ischemia is present.
    • Identify the underlying mechanism because atherothrombotic, supply-demand, procedure-related, and nonobstructive presentations require different treatment.
    • Balance ischemic and bleeding risks when choosing antithrombotic intensity and duration.
    • Start secondary prevention before discharge and ensure early follow-up and cardiac rehabilitation.
  • The greatest remaining gaps are delayed reperfusion, high mortality from cardiogenic shock, incomplete implementation of secondary prevention, and imprecise diagnosis of occlusive myocardial infarction that does not meet classic ST-elevation criteria.

Pathophysiology and Diagnostic Framework

Atherothrombotic Myocardial Infarction

  • Plaque rupture or plaque erosion exposes tissue factor and subintimal material to circulating blood.
  • This activates coagulation and platelet aggregation, producing an intracoronary thrombus that may partially or completely obstruct flow.
  • Calcified nodules are another less common substrate for acute coronary thrombosis.
  • Not every troponin elevation represents myocardial infarction. Acute myocardial injury becomes myocardial infarction only when there is evidence of acute myocardial ischemia.

Diagnostic Criteria

  • Under the Fourth Universal Definition, acute myocardial infarction required:
    • A rise and/or fall in cardiac troponin, with at least 1 value above the 99th-percentile upper reference limit.
    • At least 1 feature of myocardial ischemia:
      • Ischemic symptoms.
      • New ischemic ECG changes.
      • New pathologic Q waves.
      • Imaging evidence of new loss of viable myocardium or a new regional wall-motion abnormality in an ischemic pattern.
      • Identification of a coronary thrombus by angiography, intracoronary imaging, or autopsy.
  • Serial high-sensitivity cardiac troponin should be interpreted with the clinical context, timing of symptoms, assay-specific thresholds, ECG findings, and alternative causes of myocardial injury.
  • Common nonischemic causes of troponin elevation include myocarditis, heart failure, pulmonary embolism, renal dysfunction, tachyarrhythmia, critical illness, and sepsis.

ECG First, Troponin Second

  • Obtain and interpret the ECG immediately in suspected acute coronary syndrome.
  • Persistent ST-segment elevation or an equivalent high-risk occlusion pattern should trigger an immediate reperfusion pathway.
  • Absence of classic ST-segment elevation does not exclude acute coronary occlusion.
  • Repeat ECGs, posterior leads, right-sided leads, bedside echocardiography, and urgent cardiology review may be necessary when symptoms persist or the initial ECG is nondiagnostic.
  • The occlusive myocardial infarction (OMI) framework highlights patients with acute coronary occlusion who do not meet traditional ST-elevation myocardial infarction (STEMI) criteria. OMI is an emerging diagnostic concept and has not replaced guideline-based STEMI and non-ST-segment elevation myocardial infarction (NSTEMI) pathways.

Historical Numeric Classification

  • Type 1 myocardial infarction:
    • Spontaneous atherothrombotic infarction caused by plaque rupture, erosion, or a calcified nodule.
    • Typical management includes coronary angiography when appropriate, revascularization, dual antiplatelet therapy (DAPT), acute anticoagulation, and secondary prevention.
  • Type 2 myocardial infarction:
    • Ischemic injury caused by oxygen supply-demand imbalance from conditions such as anemia, hypoxemia, hypotension, sepsis, severe hypertension, or tachyarrhythmia.
    • Treat the precipitating condition and reassess for underlying coronary disease. Automatic activation of an atherothrombotic treatment pathway may expose patients to harm when acute coronary thrombosis is absent.
  • Type 3 myocardial infarction:
    • Cardiac death with symptoms or ECG evidence suggesting ischemia before cardiac biomarkers can be obtained or before they become abnormal.
  • Type 4 myocardial infarction:
    • Related to percutaneous coronary intervention, stent thrombosis, or restenosis under the Fourth Universal Definition.
  • Type 5 myocardial infarction:
    • Related to coronary artery bypass grafting under the Fourth Universal Definition.
  • High-sensitivity troponin assays increased recognition of acute myocardial injury and secondary myocardial infarction while making true unstable angina less common.

Risk Stratification

Why Risk Stratification Matters

  • Estimate short-term mortality and recurrent ischemic risk.
  • Identify patients who may benefit from closer monitoring or earlier invasive management.
  • Estimate bleeding risk before selecting antithrombotic intensity and duration.
  • Risk scores supplement rather than replace clinical judgment, hemodynamic assessment, ECG interpretation, frailty assessment, and evaluation of comorbid disease.

Ischemic Risk Tools

  • Global Registry of Acute Coronary Events (GRACE) score:
    • Uses age, Killip class, systolic blood pressure, heart rate, ST-segment deviation, cardiac arrest at presentation, serum creatinine, and cardiac biomarkers.
    • A GRACE score greater than 140 identifies a high-risk group frequently used in trials and guidelines when considering invasive timing.
  • Thrombolysis in Myocardial Infarction (TIMI) score for unstable angina or NSTEMI:
    • Includes age 65 years or older, at least 3 coronary risk factors, known coronary stenosis of at least 50%, ST-segment deviation, at least 2 anginal episodes in 24 hours, aspirin use within 7 days, and elevated cardiac biomarkers.
    • Predicts 14-day risk of death, myocardial infarction, or urgent revascularization.
  • TIMI score for STEMI:
    • Estimates 30-day mortality using readily available clinical variables.

Bleeding Risk Tools

  • PRECISE-DAPT uses age, creatinine clearance, hemoglobin, white blood cell count, and previous spontaneous bleeding.
  • A PRECISE-DAPT score of at least 25 indicates high bleeding risk, but its meaning depends on the population and treatment context.
  • Academic Research Consortium High Bleeding Risk (ARC-HBR) criteria define high bleeding risk as at least 1 major criterion or at least 2 minor criteria.
  • Major ARC-HBR examples include:
    • Long-term oral anticoagulation.
    • Severe or end-stage chronic kidney disease.
    • Hemoglobin below 11 g/dL.
    • Recent serious spontaneous bleeding.
    • Moderate or severe thrombocytopenia.
    • Cirrhosis with portal hypertension.
    • Active malignancy.
    • Previous spontaneous intracranial hemorrhage.
    • Recent major ischemic stroke.
    • Nondeferrable major surgery during DAPT.
  • Minor ARC-HBR examples include age at least 75 years, moderate chronic kidney disease, mild anemia, remote spontaneous bleeding, chronic steroid or nonsteroidal anti-inflammatory drug use, and previous ischemic stroke not meeting a major criterion.

High Ischemic Risk After PCI

  • Clinical enhancers include medically treated diabetes, recurrent myocardial infarction, multivessel coronary disease, premature or rapidly progressive disease, systemic inflammatory disease, polyvascular disease, and chronic kidney disease.
  • Procedural enhancers include treatment of multiple lesions, implantation of multiple stents, long total stent length, left main intervention, complex bifurcation intervention, chronic total occlusion, last remaining vessel intervention, and previous stent thrombosis during antiplatelet therapy.
  • Practical implementation remains poor. Automated risk calculation linked to specific treatment choices may improve uptake, but prospective evidence that automation improves outcomes is still needed.

STEMI: Reperfusion Is the Priority

Primary Percutaneous Coronary Intervention

  • Primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy when it can be performed promptly by an experienced team.
  • For patients presenting within 12 hours of symptom onset, immediate reperfusion is a Class I recommendation.
  • Selected patients presenting 12 to 24 hours after symptom onset may still benefit from primary PCI, particularly when symptoms or ischemia persist.
  • Patients with ongoing ischemia, hemodynamic instability, life-threatening arrhythmia, or cardiogenic shock require urgent invasive evaluation regardless of delay from symptom onset.

Fibrinolysis and the Pharmaco-Invasive Strategy

  • If primary PCI cannot be achieved within the guideline time target, generally 120 minutes from first medical contact, and there is no contraindication, administer fibrinolysis as early as possible in an eligible patient presenting within 12 hours.
  • Transfer the patient immediately to a PCI-capable center after fibrinolysis.
  • Suspect failed fibrinolysis when ST-segment resolution is less than 50% at 60 to 90 minutes, or when pain, instability, or arrhythmia persists.
  • Failed fibrinolysis requires urgent angiography and rescue PCI.
  • Even after successful fibrinolysis, routine angiography with possible PCI is recommended within 2 to 24 hours.

Procedural Strategy

  • Radial access is preferred over femoral access in most patients because it reduces major bleeding, vascular complications, and mortality.
  • Slow flow and no-reflow may persist despite opening the epicardial artery because of distal embolization, microvascular obstruction, reperfusion injury, edema, and vasoconstriction.
  • Routine manual thrombus aspiration is not recommended. Newer thrombectomy systems and real-time detection methods remain investigational.

Myocardial Infarction With Cardiogenic Shock

  • Cardiogenic shock remains a major cause of early mortality after myocardial infarction.
  • Immediate revascularization of the infarct-related artery is essential.
  • In multivessel disease with shock, the initial PCI strategy should generally treat the culprit vessel only. Routine immediate PCI of nonculprit vessels increased harm in CULPRIT-SHOCK.
  • Intra-aortic balloon pump:
    • Routine use does not improve survival in myocardial infarction-related cardiogenic shock.
    • It may still have selected roles, such as mechanical complications or individualized hemodynamic support.
  • Venoarterial extracorporeal membrane oxygenation:
    • ECLS-SHOCK did not reduce 30-day mortality with routine early use.
    • Bleeding and peripheral vascular complications increased.
    • These data argue against unselected routine use, not against carefully selected rescue use in experienced shock systems.
  • Percutaneous microaxial flow pump:
    • DanGer-Shock randomized 360 patients with STEMI-related cardiogenic shock.
    • Impella CP reduced 180-day all-cause mortality compared with standard care, but serious adverse events were more frequent.
    • The trial used restrictive eligibility criteria. The result supports protocolized selection rather than indiscriminate device placement.
  • Shock care should include rapid identification of mechanical complications, serial perfusion assessment, echocardiography, invasive hemodynamics when useful, and early multidisciplinary shock-team involvement.

Acute Antiplatelet and Anticoagulant Therapy

STEMI Undergoing PCI

  • DAPT consists of aspirin plus an oral P2Y12 inhibitor.
  • Ticagrelor or prasugrel is generally preferred over clopidogrel for patients undergoing PCI when bleeding risk is acceptable and no contraindication is present.
  • Prasugrel is contraindicated in patients with previous stroke or transient ischemic attack.
  • Clopidogrel remains appropriate when potent P2Y12 inhibition is contraindicated, unavailable, or not tolerated, and it is used with fibrinolytic therapy.
  • CELEBRATE evaluated subcutaneous zalunfiban at first medical contact in STEMI:
    • Zalunfiban improved a hierarchical 30-day composite outcome and pre-PCI infarct-related artery flow.
    • Severe or life-threatening bleeding was not significantly increased, but mild to moderate bleeding increased.
    • Zalunfiban remains an emerging strategy rather than routine standard care.
  • PCI anticoagulant options include unfractionated heparin, bivalirudin, and enoxaparin.
  • Parenteral anticoagulation should usually stop after successful PCI unless another indication exists. A protocolized post-PCI bivalirudin infusion is a specific exception when that strategy is selected.

NSTE-ACS

  • Routine oral P2Y12 pretreatment before defining coronary anatomy is not recommended when early angiography is planned because ischemic benefit is uncertain and bleeding or surgical delay may increase.
  • Pretreatment has not completely disappeared:
    • The 2025 US guideline states that clopidogrel or ticagrelor may be considered when angiography is expected to occur more than 24 hours after presentation.
    • Decisions should reflect bleeding risk, diagnostic certainty, and the probability of urgent coronary artery bypass grafting.
  • Anticoagulant options include unfractionated heparin, enoxaparin, fondaparinux, and bivalirudin.
  • When an invasive strategy will be delayed beyond 24 hours, fondaparinux or enoxaparin may be preferred over unfractionated heparin.
  • If a patient receiving fondaparinux proceeds to PCI, additional unfractionated heparin is required during the procedure to reduce catheter thrombosis.
  • Stop parenteral anticoagulation after revascularization unless another indication remains.

Complete Revascularization

  • Approximately half of patients with myocardial infarction have multivessel coronary disease.
  • In hemodynamically stable STEMI with multivessel disease, complete revascularization reduces major adverse cardiovascular events, particularly spontaneous myocardial infarction and unplanned revascularization.
  • A consistent isolated mortality benefit has not been established across all trials, so the benefit should not be summarized simply as a reduction in death.
  • Immediate versus staged treatment remains individualized:
    • BIOVASC and MULTISTARS AMI supported immediate complete revascularization as noninferior to staged treatment in selected patients.
    • OPTION-STEMI did not demonstrate noninferiority of immediate complete revascularization.
    • Differences in enrolled populations, clinical stability, lesion complexity, and outcome definitions limit direct comparison.
  • Angiographic severity, intracoronary imaging, and physiologic assessment can each inform treatment. The optimal guidance strategy is not settled for every acute myocardial infarction population.
  • In cardiogenic shock, do not extrapolate stable-patient complete revascularization data to justify routine immediate multivessel PCI.

NSTEMI: Invasive Timing Should Be Individualized

  • Immediate invasive management is indicated for hemodynamic instability, ongoing or recurrent refractory ischemia, life-threatening arrhythmia, or mechanical complications.
  • For other patients, trials comparing early and delayed angiography have not shown a consistent overall mortality or major adverse cardiovascular event benefit from an early strategy.
  • A GRACE score greater than 140 has shown a survival signal with earlier invasive treatment in subgroup analyses. This signal supports risk-based prioritization but is not proof that a single score should determine timing in isolation.
  • Contemporary interpretation is limited by older trial eras, mixed unstable angina and NSTEMI populations, variable definitions of early and delayed intervention, and differences in antiplatelet exposure.
  • Older adults:
    • A routine invasive strategy may reduce recurrent myocardial infarction or urgent revascularization without clearly reducing mortality.
    • Frailty, cognition, comorbidity, functional status, bleeding risk, life expectancy, and patient goals should be assessed explicitly.
  • Low-risk patients with uncertain NSTE-ACS may undergo selective invasive evaluation after coronary computed tomography angiography or functional testing when clinically appropriate.

Inpatient Level of Care and Transition to Discharge

  • Non-high-risk NSTE-ACS may be managed in an intermediate-care setting with continuous rhythm monitoring.
  • STEMI and high-risk NSTE-ACS require a higher-acuity setting when there is recurrent ischemia, malignant arrhythmia, cardiogenic shock, resuscitated cardiac arrest with coma, heart failure requiring ventilation, or acute kidney injury requiring renal replacement therapy.
  • Shorter hospital stays make discharge planning part of acute care rather than a final-day task.
  • Before discharge:
    • Document left ventricular ejection fraction.
    • Reconcile antithrombotic indications, duration, dose, interactions, and bleeding precautions.
    • Start intensive lipid-lowering therapy.
    • Address smoking and substance use.
    • Refer to cardiac rehabilitation.
    • Arrange early follow-up and repeat laboratory testing when needed.
    • Provide clear instructions for recurrent chest pain, dyspnea, syncope, bleeding, and medication intolerance.

Secondary Prevention

Cardiac Rehabilitation and Lifestyle

  • Cardiac rehabilitation should begin early after the acute event.
  • A comprehensive program includes exercise training, nutrition counseling, psychosocial support, medication adherence, smoking cessation, and risk-factor management.
  • Participation reduces cardiovascular hospitalization and may reduce recurrent myocardial infarction and cardiovascular mortality.
  • Return to exercise, work, and sexual activity should be individualized according to ventricular function, residual ischemia, arrhythmia, functional capacity, and the physical demands of the activity.
  • Cocaine and other stimulants are established triggers for myocardial infarction. Cannabis exposure is associated with cardiovascular risk in observational data, but causal estimates and dose-response relationships remain less certain.

Antithrombotic Therapy After Discharge

  • For patients with acute coronary syndrome who are not at high bleeding risk, the 2025 US guideline still recommends DAPT for at least 12 months as the default strategy.
  • Ticagrelor monotherapy after abbreviated DAPT is an evidence-based alternative after PCI:
    • In patients who have tolerated ticagrelor-based DAPT, transition to ticagrelor monotherapy at least 1 month after PCI is a Class I, Level A strategy to reduce bleeding.
    • This recommendation does not mean that 12-month DAPT is obsolete.
  • Other de-escalation strategies, including switching to clopidogrel after 1 month or using single antiplatelet therapy after 1 month in high bleeding risk, have weaker or more conditional recommendations.
  • Patients requiring long-term oral anticoagulation after PCI:
    • Keep triple therapy as short as possible, commonly 1 to 4 weeks depending on ischemic and bleeding risk.
    • Continue oral anticoagulation plus a single P2Y12 inhibitor, preferably clopidogrel, for the selected dual-therapy period.
    • Beyond 12 months, oral anticoagulation alone is appropriate for many stable patients, but the plan must be individualized.
  • Long-term single antiplatelet therapy:
    • Randomized trials and meta-analyses increasingly suggest that clopidogrel may reduce ischemic events compared with aspirin after successful completion of DAPT.
    • Most supporting trials enrolled post-PCI populations, and several were conducted largely in East Asian cohorts.
    • Clopidogrel should be viewed as an increasingly supported option, not a universal guideline-mandated replacement for aspirin in every patient with previous myocardial infarction.

Lipid Lowering

  • Start a high-intensity statin in all eligible patients with myocardial infarction.
  • Check baseline and follow-up low-density lipoprotein cholesterol (LDL-C), adherence, and tolerance.
  • Add nonstatin therapy early when the expected statin response will not achieve the treatment goal.
  • Options include ezetimibe, a proprotein convertase subtilisin/kexin type 9 inhibitor, and bempedoic acid.
  • Initiating ezetimibe during the index hospitalization is reasonable in very-high-risk patients or when baseline LDL-C makes goal attainment with statin monotherapy unlikely.
  • The exact LDL-C goal depends on the governing guideline. The operational principle is early, intensive, and sustained lowering rather than slow sequential escalation over many months.

Beta Blockers

  • Continue beta blockers when there is a clear indication such as reduced left ventricular ejection fraction, heart failure, angina, arrhythmia, or hypertension.
  • Preserved ejection fraction:
    • An individual-patient data meta-analysis of 5 randomized trials and 17,801 patients with ejection fraction at least 50% found no reduction in death, recurrent myocardial infarction, or heart failure.
  • Mildly reduced ejection fraction:
    • An individual-patient data meta-analysis of 4 randomized trials and 1,885 patients with ejection fraction 40% to 49% found a lower composite risk of death, recurrent myocardial infarction, or heart failure with beta-blocker therapy.
  • Long-term discontinuation:
    • SMART-DECISION found discontinuation noninferior to continuation in selected stable patients at least 1 year after myocardial infarction, with ejection fraction at least 40% and no heart failure.
    • ABYSS did not establish noninferiority of interruption in a different population and used a broader cardiovascular hospitalization endpoint.
  • Practical interpretation:
    • Reduced ejection fraction or another indication: Treat.
    • Ejection fraction 40% to 49%: Current randomized evidence supports treatment, although guideline integration continues to evolve.
    • Ejection fraction at least 50% without another indication: Routine indefinite treatment has no demonstrated prognostic benefit and should be reassessed rather than continued automatically.

SGLT2 Inhibitors

  • Sodium-glucose cotransporter 2 inhibitors have established indications in heart failure, chronic kidney disease, and type 2 diabetes with appropriate cardiovascular or renal risk.
  • DAPA-MI and EMPACT-MI did not establish a routine hard-outcome indication solely for uncomplicated myocardial infarction without diabetes, chronic kidney disease, or heart failure.
  • Use an SGLT2 inhibitor for a proven comorbid indication, not simply because myocardial infarction occurred.

Renin-Angiotensin-Aldosterone System Therapy

  • Angiotensin-converting enzyme inhibitors or angiotensin receptor blockers are strongly indicated after myocardial infarction when there is left ventricular systolic dysfunction, heart failure, hypertension, diabetes, or chronic kidney disease, unless contraindicated.
  • Mineralocorticoid receptor antagonists have an established post-myocardial infarction role in selected patients with left ventricular dysfunction plus heart failure or diabetes, with careful monitoring of potassium and renal function.
  • CLEAR did not show that routine spironolactone improves its coprimary clinical outcomes in an unselected contemporary myocardial infarction population.
  • Later meta-analyses have produced conflicting conclusions about broader use. Routine mineralocorticoid receptor antagonist therapy for all myocardial infarction survivors is therefore not established.

Anti-Inflammatory Therapy

  • Low-dose colchicine has reduced ischemic events in some coronary disease trials, including COLCOT, but results are inconsistent.
  • CLEAR randomized 7,062 patients after myocardial infarction and found no reduction in cardiovascular death, recurrent myocardial infarction, stroke, or ischemia-driven revascularization.
  • Meta-analyses that combine heterogeneous acute and chronic coronary populations may show benefit, but they do not erase the neutral result of the largest acute myocardial infarction trial.
  • Colchicine remains an optional, selective therapy rather than routine treatment for every patient after myocardial infarction.
  • Canakinumab reduced recurrent cardiovascular events in CANTOS but increased fatal infection and has not become routine post-myocardial infarction therapy.
  • Interleukin-1 and interleukin-6 pathway therapies remain investigational. ARTEMIS is evaluating ziltivekimab after acute coronary syndrome.
  • High-sensitivity C-reactive protein identifies residual inflammatory risk, but evidence is insufficient to mandate routine serial testing or to assign a specific anti-inflammatory drug solely from the result.

MINOCA: A Working Diagnosis, Not Reassurance

Definition

  • MINOCA requires:
    • Fulfillment of myocardial infarction criteria.
    • No coronary stenosis of 50% or greater in a major epicardial vessel at angiography.
    • No immediately apparent alternative explanation for the presentation.
  • Troponin elevation plus symptoms alone is not sufficient.
  • Myocarditis, takotsubo syndrome, pulmonary embolism, and other nonischemic conditions may initially mimic MINOCA and should be actively investigated.

Diagnostic Strategy

  • Reassess the angiogram for missed distal occlusion, embolism, spontaneous coronary artery dissection, or subtle plaque disruption.
  • Cardiac magnetic resonance imaging should be performed early when feasible because diagnostic yield decreases over time.
  • Intravascular ultrasound or optical coherence tomography may identify plaque rupture, plaque erosion, thrombus, or spontaneous coronary artery dissection.
  • Coronary function testing may identify epicardial spasm or coronary microvascular dysfunction.
  • Echocardiography and targeted evaluation for embolic sources, thrombophilia, arrhythmia, and structural heart disease should be guided by the clinical presentation.

Mechanism-Directed Treatment

  • Plaque disruption:
    • Treat as atherosclerotic myocardial infarction with antiplatelet therapy and intensive lipid lowering. PCI is reserved for an appropriate target lesion.
  • Coronary thromboembolism:
    • Search for atrial fibrillation, left ventricular thrombus, valve disease, endocarditis, tumor, paradoxical embolism, and selected thrombophilias.
    • Choose antiplatelet or anticoagulant therapy according to the confirmed mechanism.
  • Spontaneous coronary artery dissection:
    • Conservative management is preferred when the patient is stable and flow is preserved.
    • Use antiplatelet therapy selectively and consider beta-blockade. Avoid unnecessary PCI because intervention is technically difficult and may extend the dissection.
  • Epicardial coronary spasm:
    • Calcium channel blockers are first-line therapy.
    • Nitrates may be added for symptoms.
    • Provocative acetylcholine testing should be performed in experienced centers.
  • Coronary microvascular dysfunction:
    • Treatment is individualized and may include beta blockers, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, statins, and antianginal therapy.
  • Reported frequencies of MINOCA mechanisms vary widely by population, geography, testing strategy, and timing. Percentages from different studies should not be treated as mutually exclusive or universally applicable.
  • PROMISE supports the concept that a mechanism-directed diagnostic and treatment strategy can improve angina status, but large randomized trials powered for major clinical events remain limited.

Emerging Directions

  • Artificial intelligence-assisted ECG interpretation may improve detection of acute coronary occlusion that does not meet traditional STEMI criteria.
  • TITAN-OMI and DIFOCCULT-3 are evaluating whether AI-assisted OMI recognition improves clinical outcomes. Until outcome data are available, AI should support rather than replace expert ECG interpretation and clinical judgment.
  • Parenteral antiplatelet treatment before PCI is being revisited:
    • Zalunfiban is administered by a clinician at first medical contact.
    • Selatogrel is being studied as patient self-administration after recurrent symptoms in patients with previous myocardial infarction.
  • The central challenge is not only developing new drugs or devices. Systems must also reduce first-medical-contact-to-reperfusion delay and reliably deliver proven secondary prevention.

Practical Myocardial Infarction Checklist

First Minutes

  • Obtain and interpret a 12-lead ECG immediately.
  • Repeat the ECG and obtain posterior or right-sided leads when indicated.
  • Assess airway, breathing, circulation, perfusion, arrhythmia, and heart failure.
  • Activate reperfusion immediately for STEMI or a convincing occlusion pattern.
  • Draw serial high-sensitivity troponin without delaying reperfusion when the ECG already establishes the need.

Acute Treatment

  • Give aspirin unless contraindicated.
  • Select P2Y12 inhibition according to reperfusion strategy, bleeding risk, stroke history, oral anticoagulation, and likelihood of coronary artery bypass grafting.
  • Choose anticoagulation according to STEMI or NSTE-ACS strategy and expected timing of angiography.
  • Prefer radial access for PCI when feasible.
  • In shock, revascularize the culprit artery and avoid routine immediate nonculprit PCI.

Before Discharge

  • Confirm the mechanism of myocardial infarction rather than relying only on the STEMI or NSTEMI label.
  • Document left ventricular function and heart failure status.
  • Write an explicit antithrombotic plan with start date, stop date, and reasons.
  • Start high-intensity statin therapy and add early nonstatin treatment when needed.
  • Reassess the need for beta blockers, renin-angiotensin system therapy, mineralocorticoid receptor antagonists, and SGLT2 inhibitors according to ejection fraction and comorbid indications.
  • Refer to cardiac rehabilitation and arrange early follow-up.

Final Take-Home Points

  • ECG determines urgency, while serial troponin and clinical evidence determine whether acute myocardial injury is myocardial infarction.
  • Acute coronary occlusion may occur without classic ST-segment elevation. Persistent ischemic symptoms with a nondiagnostic ECG require repeated and expanded assessment.
  • STEMI care is a race to reperfusion. Use primary PCI when timely; otherwise use fibrinolysis followed by immediate transfer and a pharmaco-invasive strategy in eligible patients.
  • Cardiogenic shock requires culprit-vessel revascularization and selective, protocolized use of mechanical support rather than routine device placement.
  • Complete revascularization benefits stable multivessel disease, but the timing and method of lesion selection remain individualized.
  • For NSTEMI, invasive timing depends on instability, recurrent ischemia, overall risk, frailty, and the expected delay to angiography. Earlier is not automatically better for every stable patient.
  • Twelve-month DAPT remains the default for patients without high bleeding risk. Ticagrelor monotherapy after at least 1 month is a validated bleeding-reduction option after PCI, not a universal replacement for standard DAPT.
  • Long-term beta-blocker benefit depends strongly on left ventricular ejection fraction and other indications.
  • MINOCA is a working diagnosis that requires cardiac magnetic resonance imaging, careful angiographic review, intracoronary imaging, and/or coronary function testing to identify a treatable mechanism.
  • Secondary prevention should begin during the index hospitalization and should be treated with the same urgency as reperfusion.

Selected References

Educational summary. Confirm current guidelines, contraindications, dosing, renal function, bleeding risk, and local reperfusion protocols before clinical use.

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