Non-ST-elevation myocardial infarction (NSTEMI)

Article written and reviewed by Dr Luca Moretti

Non-ST-elevation myocardial infarction, or NSTEMI, is an acute infarction defined by the combination of dynamic cardiomyocyte injury and evidence of ischemia. The absence of a STEMI pattern does not mean the absence of occlusion or a minor event: it describes the tracing at the time it is recorded, not the vessel, necrotic mass, or individual risk. Diagnosis requires a rise and/or fall in cardiac troponin, with at least one value above the assay's sex-specific 99th percentile, together with ischemic symptoms, new ECG changes, Q waves, compatible imaging, or a coronary thrombus. An isolated elevated troponin instead represents myocardial injury and must be interpreted without automatically assigning an atherothrombotic mechanism.

NSTEMI belongs to the spectrum of acute coronary syndromes without persistent ST-segment elevation. It is distinguished from unstable angina by acute myocardial injury associated with ischemia: high-sensitivity troponins now identify many cases formerly classified as angina as small infarctions. The etiologic distinction is between primary myocardial infarction, caused by an acute coronary disorder such as atherothrombosis, and secondary myocardial infarction, caused by a supply-demand imbalance resulting from another acute condition. Both may present as NSTEMI, but antiplatelet therapy, coronary angiography, and prevention cannot be applied indiscriminately.

Management proceeds simultaneously along four axes: recognizing possible occult occlusion, confirming or excluding infarction through serial measurements, estimating ischemic and bleeding risks, and identifying the mechanism. Repeated ECGs, high-sensitivity troponin, echocardiography, and clinical assessment determine urgency; coronary angiography defines the anatomy and potential for revascularization. Invasive access is immediate in unstable patients. In others, the strategy during hospitalization is tailored to risk, comorbidities, and diagnostic probability, avoiding both dangerous delays and automatic procedures in a nonischemic presentation.

Etiology, risk factors, pathogenesis, and pathophysiology

In primary NSTEMI due to atherothrombosis, the most common substrate is a complicated atherosclerotic plaque. Cap rupture exposes highly thrombogenic material; erosion causes loss of the endothelial barrier over a plaque that is often less lipid-rich; less commonly, a calcified nodule disrupts the luminal surface. Platelet adhesion, P2Y12 and thromboxane activation, and thrombin and fibrin generation build a thrombus that may reduce flow without causing stable occlusion. Thrombosis is dynamic: propagation, fragmentation, distal embolization, and spontaneous fibrinolysis explain intermittent pain, transient ECG changes, and an apparently patent lesion at angiography. Residual stenosis alone does not reconstruct the severity of the event.

The non-ST-elevation phenotype may result from incomplete occlusion, early recanalization, collateral flow, a small territory, or an electrical vector not recognized by the 12 standard leads. Occlusion of the circumflex, a diagonal or marginal branch, or posterior ischemia may not produce the classic pattern; diffuse depression with elevation in aVR may signal extensive ischemia but does not by itself identify left main disease. The old equivalence between NSTEMI and nontransmural infarction is therefore imprecise. CMR may show subendocardial necrosis but also deeper involvement; conversely, rapid reperfusion of a STEMI may leave only a limited scar.

Secondary myocardial infarction does not involve an acute coronary disorder: severe anemia, hypoxemia, hypotension, shock, tachyarrhythmia, bradyarrhythmia, or a hypertensive crisis may cause a supply-demand imbalance; coronary vasospasm, by contrast, is a possible etiology of primary myocardial infarction. Fixed coronary disease lowers the threshold but is not required; hypertrophy and microangiopathy increase demand or limit supply. Without clinical evidence of ischemia, the condition must be termed myocardial injury, not NSTEMI, and it is acute only when troponin rises and/or falls. Sepsis, pulmonary embolism, myocarditis, heart failure, and kidney failure may cause a troponin dynamic through different mechanisms. The correct label is a pathophysiological decision, not merely a comparison with a laboratory limit.

Factors driving coronary atherothrombosis include cumulative exposure to LDL and apoB, lipoprotein(a), smoking, hypertension, diabetes, chronic kidney disease, and familial predisposition. Age and previous vascular disease express burden rather than isolated causation; systemic inflammation, adrenergic stress, and a prothrombotic state may precipitate an event over a pre-existing plaque. Diabetes combines diffuse disease, microvascular dysfunction, and increased platelet reactivity; nephropathy combines calcification, anemia, inflammation, and bleeding risk. In younger patients, genetic dyslipidemias, stimulants, selected thrombophilias, and nonatherosclerotic causes should be considered.

Spontaneous coronary artery dissection causes ischemia by compression of the true lumen by an intramural hematoma and is relevant in younger women, the peripartum period, and arteriopathies. Embolism may arise from atrial fibrillation, endocarditis, prosthetic valves, a ventricular thrombus, or paradoxical passage; vasospasm may transiently narrow an epicardial coronary artery, while microvascular dysfunction alters flow without an obstructive lesion. These mechanisms may produce the same biomarker and ECG findings as primary myocardial infarction due to atherothrombosis. A targeted history and coronary or intravascular imaging prevent the NSTEMI label from becoming a false etiologic explanation.

Ischemia interrupts oxidative phosphorylation, reduces ATP, disrupts calcium handling, and first impairs relaxation, then contractility and electrical stability. The subendocardium is vulnerable because of greater wall stress, systolic compression, and dependence on diastolic perfusion; tachycardia and hypotension further shorten or reduce supply. If ischemia persists, loss of membrane integrity releases troponin. Reperfusion may salvage tissue but leave stunning, edema, and microvascular obstruction. Inflammation and repair replace necrotic cells with scar, while the extent of loss determines dysfunction, remodeling, and arrhythmic risk.
The relationship between plaque and thrombus is not static. An angiographically severe stenosis may be coincidental stable disease, whereas a moderate plaque may have produced thrombosis and recanalization; culprit status requires concordance among territory, morphology, and presentation. The presence of multiple vulnerable lesions explains future events remote from the treated segment. Lipid-lowering therapy stabilizes the system, not merely the PCI site.

Hemorrhagic stress deserves attention: occult bleeding, anemia, and hypotension may cause secondary myocardial infarction, while empirical antithrombotic therapy may aggravate the precipitant; conversely, hemorrhage may activate catecholamines and plaque thrombosis, producing concomitant primary myocardial infarction due to atherothrombosis. Temporal sequence and anatomy prevent a false either-or choice. The two mechanisms may coexist in the same patient.
Acute factors such as air pollution, cold, infections, and psychological stress may increase vascular tone, inflammation, and thrombogenicity; they do not replace chronic causal factors but help explain the temporal clustering of events in vulnerable people. Prevention remains focused on established modifiable exposures. No test predicts the day on which an individual plaque will become complicated.

The circadian rhythm of events reflects sympathetic activation, blood pressure, platelet activity, and behavior. The morning increase is not a rule for an individual patient and does not change the need to assess symptoms at any hour; sleep apnea, fragmented sleep, and shift work may exacerbate stress and risk. Correcting them complements prevention but does not replace LDL, smoking, and blood-pressure control. Pathophysiology combines chronic exposure and transient precipitants.

Pathological anatomy, classification, and course

The initial classification separates NSTE-ACS from STEMI on the basis of the ECG, whereas the universal classification assigns the type according to mechanism. An NSTEMI may be a primary, secondary, or procedure-related myocardial infarction; stent thrombosis or restenosis is procedure-related when it occurs within 30 days and is classified as primary myocardial infarction when it occurs after 30 days. A complete report should therefore state the presentation, etiologic type, location, function, and complications. The term “subendocardial” describes an anatomical distribution and does not replace NSTEMI. Similarly, “non-Q-wave” is historical nomenclature: Q waves may appear after NSTEMI, and not every STEMI produces them.

The culprit lesion often shows rupture, erosion, or thrombus over protruding calcium. Angiography depicts the lumen and may identify stenosis, thrombus, dissection, and TIMI flow but does not always characterize the wall; OCT has sufficient resolution to assess the cap, thrombus, and subtle dissections, whereas IVUS measures burden, diameters, and deeper calcium. Intravascular imaging does not mean indiscriminate investigation. It is particularly useful when the anatomy does not explain the event, the lesion is ambiguous, the left main artery is involved, or complex PCI must be optimized.
Necrosis is frequently subendocardial and multifocal, especially when microemboli are distributed distally, but size and depth depend on duration, collaterals, demand, and reperfusion. CMR with late gadolinium enhancement identifies an ischemic pattern that begins in the endocardium and follows a coronary territory; myocarditis tends to have a nonischemic distribution, whereas Takotsubo syndrome shows edema with no or minimal typical scar. Microvascular obstruction and intramyocardial hemorrhage are less common than in large STEMIs but indicate more severe injury when present.

ECG evolution may include ST depression, symmetric T-wave inversion, transient changes, or a normal tracing. Depression in multiple leads reflects a global subendocardial vector but does not precisely localize the culprit; dynamic changes during pain increase the probability of ischemia; deep anterior T waves after symptom resolution may suggest critical proximal LAD stenosis. A normal initial ECG does not end the pathway: intermittent ischemia and electrically silent territories require serial recordings and selected additional leads.

The troponin dynamic depends on sampling time, necrotic mass, reperfusion, kidney function, and the analytical method. A very high value increases the probability of infarction, but no concentration perfectly separates primary myocardial infarction, secondary myocardial infarction, and nonischemic injury; absolute changes are often more useful near the cutoff, and when values are chronically elevated, a significant change must be demonstrated in the clinical context. When early reinfarction is suspected, serial cardiac troponin, the ischemic presentation, and often coronary angiography are central; CK-MB adds cost without providing diagnostic clarity.

After stabilization, scar and stunned myocardium follow different trajectories. Regional function may recover over weeks, whereas permanent scar supports remodeling and electrical re-entry; a small NSTEMI with treated anatomy may recover well, while an extensive event, multivessel disease, or kidney failure may generate high late risk even without initial complications. The course does not end at discharge: restenosis, stent thrombosis, progression of nonculprit plaques, and inadequate lipid control account for recurrences, while bleeding and comorbidities alter the ability to maintain effective therapies.
Necrosis may be focal or multifocal. Distal microemboli produce small separate areas, whereas prolonged stenosis creates a more continuous subendocardial band; their sum may produce a substantial biomarker peak without a large Q wave. On CMR, the number and location of lesions help distinguish procedure-related embolization from spontaneous primary myocardial infarction. Image quality and examination timing affect interpretation.

The Killip classification describes hemodynamic involvement from no heart failure to shock and retains prognostic value; it is not anatomical: a Killip I patient may have a critical lesion, while congestion may result from previous dysfunction. The class should be recorded at presentation and updated. Its evolution is more informative than a static label.
In a patient with previous bypass surgery, the anatomy includes grafts and native vessels. A degenerated saphenous vein graft may embolize, an internal mammary graft may remain patent while native disease progresses, and collaterals may conceal occlusion; planning should use operative reports and minimize contrast. PCI of the native vessel is often preferable to treatment of the vein graft when technically feasible. The choice requires experienced operators.

Nonculprit plaques may show a high burden and high-risk features, but their treatment depends on severity and functional evidence, not vulnerability alone. Research pancoronary imaging has improved understanding without creating an indication for generalized preventive stenting; progression is addressed with systemic therapy and symptom follow-up. New ischemia requires renewed anatomical assessment. Risk is diffuse, while the procedure is local.

Clinical manifestations

The typical presentation is retrosternal chest discomfort that is pressing or constricting, occurs at rest or with minimal exertion, and lasts longer than usual. It may radiate to the arms, shoulders, jaw, neck, back, or epigastrium; sweating, nausea, and a sense of impending death increase suspicion but are not specific. Response to nitrates or antacids neither confirms nor excludes the diagnosis. Pain intensity and surface area do not measure the extent of necrosis.
Dyspnea may replace pain, particularly in older adults and patients with diabetes, nephropathy, or heart failure. Sudden weakness, syncope, confusion, isolated nausea, and functional deterioration are less recognizable but clinically important presentations; women often report pain together with more associated symptoms, and calling these “atypical” may lead to underestimation. Cardiac arrest or a tachyarrhythmia may be the first manifestation. The absence of pain at the time of assessment does not exclude an ischemic episode that has already resolved.

Physical examination is often normal but must identify hemodynamic instability, congestion, and complications. Hypotension, cold extremities, oliguria, or altered mental status suggest low output; crackles, a third heart sound, and hypoxemia indicate heart failure; a new systolic murmur requires urgent echocardiography for mitral regurgitation or a septal defect. Pulse asymmetry and tearing pain suggest aortic dissection; disproportionate hypoxemia, signs of venous thrombosis, and right-sided overload suggest pulmonary embolism. The differential diagnosis proceeds alongside stabilization.
Recurrent pain despite treatment, dynamic ST changes, instability, acute heart failure, and life-threatening arrhythmias define a very-high-risk profile that must not wait for completion of an ordinary serial pathway; these signs may indicate evolving thrombosis, intermittent occlusion, or a large mass at risk. Conversely, a fleeting symptom with an unchanged ECG and low serial troponins may represent lower risk, but the decision must consider time from onset and the quality of the history.

The history addresses previous infarction, PCI or bypass, the usual anginal pattern, medications, bleeding, stroke, kidney failure, and allergies. Anticoagulants, the time of the last dose, and adherence alter the antithrombotic strategy; metformin, kidney function, and previous contrast reactions influence the pathway but are not automatic contraindications to angiography. Fever, anemia, hemorrhage, infection, hypoxia, and tachyarrhythmia may be precipitants or the dominant diagnosis. Their temporal relationship to ischemia is essential in classifying infarction type.
Clinical risk is continuous. Age, systolic pressure, heart rate, creatinine, Killip class, cardiac arrest, ST deviation, and biomarkers constitute the GRACE score, which estimates mortality and supports decisions; bleeding risk considers anemia, previous bleeding, kidney function, age, and the need for anticoagulation. No score overrides an emergency sign: shock, refractory ischemia, or an unstable arrhythmia requires immediate management even before formal calculation.

In frail older adults, delirium, falls, dyspnea, and instability are more common than isolated pain. Polypharmacy, nephropathy, and anemia increase bleeding, but revascularization may still offer substantial benefit if the anatomy is treatable; assessment of cognition, independence, and goals supports shared decision-making. Chronological age does not define futility.
In diabetes, neuropathy and autonomic dysfunction attenuate pain, while diffuse and microvascular ischemia impairs function; excessively aggressive glucose control during the acute phase creates a risk of hypoglycemia, so extremes are avoided and treatment is reassessed after stabilization. Multivessel disease requires a strategy that considers complexity and ejection fraction. Bypass may be preferable in selected anatomies.

After recurrence, the history distinguishes postinfarction angina, pericarditis, procedural pain, and new thrombosis; positional pleuritic pain suggests a pericardial cause, whereas territorial changes and instability favor ischemia, and both may coexist. Attributing every symptom to an already diagnosed infarction delays recognition of aortic disease, embolism, or bleeding. Reassessment must start again from pathophysiology.
The Killip class may worsen during observation because of recurrent ischemia, fluids, arrhythmia, or a complication. New crackles, falling saturation, and reduced urine output require an ECG, echocardiography, and review of the invasive strategy; monitoring is not identical for everyone: duration and intensity follow arrhythmic risk, function, and revascularization. A small uncomplicated event needs less telemetry than dynamic ischemia. Surveillance should have explicit clinical objectives.

Investigations and diagnosis

The 12-lead ECG should be obtained and interpreted rapidly. In NSTEMI it may show ST depression, T-wave inversion, transient abnormalities, or no changes; repeated tracings during recurrence increase sensitivity. V7-V9 are useful when depression in V1-V3 suggests posterior ischemia, and right-sided leads when an inferior infarction coexists. Resolved transient ST elevation does not make the case benign. An occlusion pattern without classic criteria and with persistent ischemia requires an urgent strategy serving the same purpose as reperfusion.
High-sensitivity troponin is measured at presentation and according to a test-specific, validated 0/1-hour or 0/2-hour algorithm. Thresholds are not interchangeable among manufacturers and combine the initial value and absolute delta; the rule-out zone identifies a very low probability only when sampling is appropriate; the observation zone requires another measurement and investigations; the rule-in zone increases probability but does not prove primary myocardial infarction. Very early onset, recurrent pain, kidney failure, and chronically elevated values require cautious interpretation.

Criteria of the Fifth Universal Definition for acute myocardial infarction

• Rise and/or fall in cardiac troponin with at least one value above the sex-specific 99th percentile of the upper reference limit.
• At least one item of evidence of acute ischemia: symptoms; new or presumed new ischemic ECG changes; new pathological Q waves; imaging evidence of an acute coronary disorder; or new or presumed new loss of viable myocardium or a regional abnormality with an ischemic distribution.
• NSTEMI classification requires the absence of persistent ST-segment elevation defining the STEMI pathway; the etiologic type must be assigned separately.

Complete blood count, creatinine, electrolytes, glucose, coagulation, and the lipid profile define safety and risk. Anemia may precipitate secondary myocardial infarction or increase bleeding risk; potassium and magnesium abnormalities promote arrhythmias; kidney function guides dosing and contrast use. BNP or NT-proBNP provides prognostic information in heart failure but does not diagnose infarction. Chest radiography is reserved for congestion and alternative diagnoses. D-dimer and CT angiography follow reasoned suspicion of embolism or aortic disease, not indiscriminate ordering.
Echocardiography assesses regional abnormalities, ejection fraction, the right ventricle, valves, and complications. A normal examination does not exclude a small NSTEMI, whereas new dysfunction increases probability and risk; during instability it rapidly identifies left-, right-, or mechanically mediated shock. Coronary angiography defines stenosis, flow, and strategy; FFR and iFR have limitations in the acute culprit lesion because the microcirculation and vasomotor tone are altered, but may help with selected nonculprit lesions. OCT and IVUS clarify the mechanism and optimize implantation.

The possibility of MINOCA arises when no stenosis reaches 50%. It is a working diagnosis: ventriculography or echocardiography, early CMR, intravascular imaging, and selected vasomotor tests distinguish plaque, embolism, dissection, spasm, myocarditis, and Takotsubo syndrome; labeling the patient as having “normal coronary arteries” improperly ends the investigation. CMR is also useful when symptoms and biomarkers are discordant but must not delay coronary angiography required for active ischemia.
The differential diagnosis includes injury caused by sepsis, heart failure, pulmonary embolism, hypertensive crisis, tachyarrhythmia, kidney failure, myocarditis, and Takotsubo syndrome. Reproducible or alternative pain reduces the probability but does not eliminate it, and coexistence is possible; the final classification must be reassessed after anatomy and imaging, avoiding retention of “NSTEMI” as a provisional code when the data demonstrate another mechanism. Before discharge, infarction type, culprit lesion, revascularization, ventricular function, antithrombotic therapy, and the follow-up plan should be documented.

Pretest probability changes the value of every result. A small delta near the cutoff in a patient with typical pain and dynamic ST changes carries a different weight from the same value during asymptomatic nephropathy; accelerated algorithms were developed for suspected infarction, not indiscriminate screening of asymptomatic people. Used outside their context, they generate overdiagnosis and procedures.
GRACE 2.0 estimates mortality, whereas ARC-HBR and PRECISE-DAPT describe bleeding-related aspects in specific settings; the scores are not interchangeable and do not authorize addition of numbers without understanding their population and time frame. Invasive decisions and antithrombotic duration derive from net benefit. Clinical judgment remains necessary in underrepresented populations.

When troponin is chronically elevated, previous values are valuable. Nephropathy may keep concentrations above the percentile, but a significant change with ischemia still identifies an infarction; a flat curve indicates chronic injury; kidney function influences concentration and prognosis but does not make the biomarker useless. Sex and assay may alter the reference limit.
In suspected late presenters, troponin may already be falling and the ECG may show evolved T or Q waves. The history and imaging demonstrate a recent event even without a large delta between closely spaced samples; the invasive decision depends on symptoms, instability, viability, and anatomy, not on a peak that has already passed. CMR may approximately date edema and scar. Delay does not justify denying the diagnosis.

Treatment and prognosis

Initial treatment includes monitoring, intravenous access, aspirin, and ischemia control. Oxygen is indicated in hypoxemia, particularly when saturation is below 90%, and is not routinely recommended in normoxemic patients; sublingual or intravenous nitrates reduce pain and congestion when blood pressure, the right ventricle, and PDE5-inhibitor use permit; morphine is reserved for severe pain because it may cause hypotension and delay P2Y12 absorption. Oral beta-blockers are appropriate in stable patients without heart failure, low output, bradycardia, or risk of shock.
Aspirin is combined with a P2Y12 inhibitor when NSTEMI is confirmed and the strategy has been defined. If early angiography is planned and the anatomy is unknown, routine pretreatment is not recommended: ACCOAST showed more bleeding without benefit when prasugrel was administered before angiography, and early loading may complicate urgent bypass surgery. Once PCI is selected, prasugrel or ticagrelor is preferred to clopidogrel in appropriate patients; clopidogrel is used when bleeding risk, age, anticoagulation, contraindications, or availability make the more potent drugs unsuitable.

Parenteral anticoagulation is selected according to the invasive pathway: unfractionated heparin during PCI; fondaparinux is effective in NSTE-ACS management but requires an additional heparin bolus at PCI to prevent catheter thrombosis; enoxaparin is an alternative with kidney-adjusted dosing. Unnecessary switching among anticoagulants increases errors and bleeding. IIb/IIIa inhibitors are not routine and are reserved for bail-out treatment of thrombus, no-reflow, or complications. Fibrinolysis is not indicated in NSTEMI.
An immediate invasive strategy is required for shock or instability, refractory or recurrent pain despite treatment, life-threatening arrhythmias, a mechanical complication, or heart failure clearly related to ischemia. In patients with confirmed NSTEMI, a high GRACE score, or other high-risk features, coronary angiography during hospitalization reduces events; a procedure within 24 hours should be considered in high-risk patients, but the benefit of exact timing is greater in high-risk subgroups and does not justify a race against the clock in a stable patient. Advanced age, frailty, and nephropathy require individualized assessment, not automatic exclusion.

PCI preferentially uses radial access, drug-eluting stents, and intravascular imaging for complex lesions. Bypass is preferable in left main or complex multivessel anatomy, selected patients with diabetes, or when complete percutaneous revascularization is unreasonable; the Heart Team decision considers urgency and the need to stop P2Y12 therapy. A conservative strategy is appropriate when the diagnosis or invasive benefit is unlikely, procedural risk is disproportionate, or informed preferences support it. “Conservative” does not mean absence of treatment or etiologic investigation.

DAPT has a default duration of 12 months in the absence of high bleeding risk, but it may be shortened, de-escalated, or followed by monotherapy in selected patients. When oral anticoagulation is indicated, triple therapy is maintained for the shortest period compatible with thrombosis risk and generally followed by an anticoagulant plus clopidogrel. Prevention includes a high-intensity statin, early addition of ezetimibe or further therapy according to LDL and risk, smoking cessation, blood-pressure and diabetes control, physical activity, and rehabilitation. ACE inhibitors or ARBs, mineralocorticoid antagonists, and heart-failure therapy follow function and comorbidities.

Initial prognosis is determined by shock, cardiac arrest, Killip class, ST deviation, troponin, kidney function, age, and anatomy; late prognosis by ejection fraction, multivessel disease, diabetes, recurrence, bleeding, and adherence. Compared with STEMI, in-hospital mortality may be lower, but the greater burden of age and comorbidities makes long-term risk at least comparable in many cohorts. Discharge requires medication reconciliation, an explanation of DAPT, lipid assessment at four to eight weeks, rehabilitation, and instructions about symptoms of recurrence or bleeding.
Anti-ischemic therapy respects the hemodynamic profile. Nitrates help hypertensive congestion but are dangerous in hypotension or right-sided involvement; beta-blockers reduce demand but are not initiated during shock; calcium-channel blockers are reserved for spasm or selected control and do not replace prognostic medication. Every drug must have a verifiable indication.

Revascularization of nonculprit lesions in NSTE-ACS is individualized. Severity, physiology, imaging, kidney function, and completeness determine whether treatment occurs during the index or a staged procedure; an uncertain lesion should not be treated merely because it is visible. In left main or complex multivessel disease, comparison of PCI and CABG considers surgical risk and antithrombotic therapy. The Heart Team is useful when both strategies are plausible.
Discharge addresses medication adherence, costs, interactions, and understanding. Prematurely stopping P2Y12 therapy after stenting may cause thrombosis, whereas duplicating anticoagulants or NSAIDs increases bleeding; the patient receives a reconciled list, planned duration, and a contact for future procedures. Rehabilitation corrects errors before they cause events.

When oral anticoagulation is indicated, a DOAC is generally preferred to warfarin except with mechanical valves, rheumatic mitral stenosis, or other exceptions. Aspirin is stopped early in most patients after a brief period of triple therapy, with continuation of an anticoagulant and clopidogrel; duration and dosing depend on thrombosis, bleeding, and kidney function. An unjustified reduced regimen may compromise embolic protection. The plan must be written and shared.

Complications

Recurrent ischemia may result from persistent thrombus, spasm, incomplete revascularization, or progression. New pain with ECG changes requires reassessment and often angiography; if troponin remains elevated, a renewed rise from stable or falling values supports reinfarction in the appropriate setting. Stent thrombosis may be acute, subacute, or late and is promoted by interruption of DAPT, underexpansion, malapposition, and complexity. Intravascular imaging helps correct the mechanism.
Heart failure results from myocardial loss, persistent ischemia, stunning, mitral regurgitation, or arrhythmia. Pulmonary edema and shock require echocardiography and urgent revascularization when ischemia is causal; diuretics, vasodilators, vasopressors, and inotropes are selected according to congestion and perfusion. Shock may be left-sided, right-sided, biventricular, or mechanical. An apparently preserved ejection fraction does not exclude low output caused by acute mitral regurgitation.

Early ventricular arrhythmias reflect ischemia and electrical instability; ventricular fibrillation requires defibrillation, while polymorphic tachycardia requires correction of ischemia and electrolytes. Atrial fibrillation impairs filling and increases embolic risk, complicating the combination of anticoagulants and antiplatelet drugs. Bradycardia and blocks are less typical than in an inferior STEMI but may occur. The decision regarding an implantable defibrillator is generally deferred until function and treatment have been reassessed after recovery.
Mechanical complications are less frequent than after large unreperfused STEMIs but remain possible: papillary-muscle rupture or ischemic dysfunction causes mitral regurgitation, a septal defect produces a shunt, and free-wall rupture causes tamponade. A new murmur, sudden edema, hypotension, or electromechanical dissociation requires urgent imaging and cardiac surgery. Apical infarction may promote a ventricular thrombus, especially with extensive akinesia; contrast echocardiography or CMR increases sensitivity, and anticoagulation is balanced against DAPT.

Gastrointestinal, intracranial, or access-site bleeding increases mortality and may force interruption of protective therapies. Radial access, correct kidney-adjusted doses, proportionate P2Y12 inhibition, gastroprotection in at-risk patients, and brief triple therapy reduce risk; acquired anemia impairs oxygen supply, and transfusion thresholds must be individualized. Thrombocytopenia requires differentiation among drugs, sepsis, and heparin-induced thrombocytopenia.
Acute kidney injury often results from shock, congestion, age, diabetes, and nephrotoxic agents as well as contrast. Stable hemodynamics, minimal contrast volume, and correct dosing are essential; delaying a life-saving procedure solely because of renal fear may be more harmful. Ischemic stroke may result from atrial fibrillation, ventricular thrombus, or the procedure, whereas hemorrhagic stroke is promoted by antithrombotic intensity. Infections, delirium, deconditioning, and falls particularly complicate older patients and should be included in the plan from admission.

Over the long term, remodeling, scar, and residual ischemia may progress to ischemic cardiomyopathy, functional mitral regurgitation, ventricular tachycardia, and sudden death. Depression, anxiety, and fear of exertion impair adherence and recovery; rehabilitation and integrated follow-up therefore have prognostic, not merely symptomatic, value. Risk is not confined to the culprit lesion: untreated plaques, LDL, Lp(a), smoking, and diabetes sustain the possibility of another infarction, stroke, and peripheral disease. Secondary prevention is part of treatment of the acute event.
Early pericarditis causes pleuritic pain, a rub, and sometimes diffuse ST changes in the following days. It must be distinguished from reinfarction and contained rupture; echocardiography looks for effusion and the biomarker curve is interpreted in context. Dressler syndrome occurs later and is immune mediated. Treatment avoids inappropriate NSAIDs in the early postinfarction period.

Ischemic mitral regurgitation may be dynamic without rupture, resulting from tethering and papillary dysfunction. A faint murmur does not exclude severe regurgitation during shock because the gradient may be low; transesophageal echocardiography clarifies the mechanism. Revascularization, afterload reduction, and support treat the acute phase. Valve intervention depends on persistence and anatomy.
Depression, post-traumatic stress, and deconditioning influence mortality through inactivity and poor adherence. Screening, risk communication, and rehabilitation reduce fear of exertion; resumption of driving, work, and sexual activity should be individualized according to stability. Vague instructions promote avoidance and loss of independence.

Late sudden death results primarily from scar, dysfunction, and arrhythmias. Ejection fraction is reassessed after treatment and a recovery period before a primary-prevention ICD; late sustained arrhythmias may create different indications; prolonged monitoring is selective for syncope, palpitations, or documented arrhythmias. Fear alone does not justify indefinite testing. Rehabilitation and education in recognizing symptoms complete prevention.