Acute coronary syndromes

Article written and reviewed by Dr Luca Moretti

Acute coronary syndromes are clinical presentations caused by a sudden reduction in myocardial perfusion and include ST-elevation myocardial infarction, non-ST-elevation myocardial infarction, and unstable angina. They are time-dependent emergencies: diagnosis, antiplatelet therapy, anticoagulation, and revascularization must be coordinated without avoidable delay, but tailored to the mechanism and to ischemic and bleeding risk.
The term acute coronary syndrome represents a working diagnosis at admission. The ECG immediately separates patients with persistent ST-segment elevation or occlusion equivalents, in whom reperfusion is urgent, from those without this presentation. High-sensitivity cardiac troponin subsequently distinguishes infarction from unstable angina, while coronary angiography and imaging may clarify anatomy and mechanism.

STEMI and NSTEMI are both infarctions: the electrocardiographic difference guides the initial strategy but does not directly measure the depth of necrosis. An acute occlusion may not produce classic ST-segment elevation, for example in a posterior territory, in the presence of collateral circulation, or with particular electrical patterns. Conversely, pericarditis, early repolarization, and other conditions may mimic ST-segment elevation.
Myocardial infarction requires ischemic necrosis. An increase in troponin without evidence of ischemia is myocardial injury, not infarction. Primary myocardial infarction occurs spontaneously because of acute coronary pathology, most often atherothrombosis but also spontaneous coronary artery dissection, embolism, or vasospasm; secondary myocardial infarction instead results from a supply-demand imbalance caused by another acute condition and requires a strategy centered on the precipitant.

Coronary angiography showing no stenosis of at least 50% does not end the diagnostic process. MINOCA is a working diagnosis of myocardial injury with nonobstructive coronary arteries. Magnetic resonance may identify myocarditis or Takotsubo syndrome, whereas intracoronary imaging may clarify atherothrombosis, dissection, or other coronary mechanisms; the final diagnosis is then reclassified according to the identified cause.
Despite improved emergency networks, mortality remains high in patients with shock, cardiac arrest, a large anterior infarction, advanced age, kidney disease, and frailty. Prognosis does not end at discharge: recurrence, heart failure, arrhythmias, and bleeding remain possible, whereas the burden of nonculprit atherosclerosis requires intensive secondary prevention.

Etiology, risk factors, pathogenesis, and pathophysiology

The most common cause is formation of a thrombus over a complicated atherosclerotic plaque. Blood comes into contact with matrix and thrombogenic material, platelets adhere through von Willebrand factor and specific receptors, become activated, and recruit other platelets; tissue factor initiates coagulation, thrombin amplifies aggregation and converts fibrinogen to fibrin. Vasoconstriction and reduced fibrinolysis may increase occlusion.
Plaque rupture creates a communication between the lumen and necrotic core through a disrupted cap. It is associated with a large lipid burden, thin cap, inflammation, and expansive remodeling, but no feature deterministically predicts the fate of an individual lesion. Risk also depends on the patient’s systemic thrombotic and inflammatory state.

In surface erosion, thrombus adheres to a denuded surface with an apparently intact cap. The plaque is often rich in proteoglycans and smooth-muscle cells and less lipid-rich. Disturbed flow, innate immune receptors, neutrophils, and NETs participate in the mechanism. OCT may suggest erosion, but does not directly visualize the endothelial layer, and the in vivo diagnosis remains inferential.
Eruptive calcified nodules are less common and occur in severely calcified and tortuous arteries. Calcific fragments protrude, disrupt the surface, and sustain thrombosis. They are more common in older people, diabetes, and kidney disease and may make lesion preparation and stent expansion difficult.

The thrombus is not static. Propagation, distal embolization, vasoconstriction, endogenous lysis, and reformation may alternate. A persistent complete occlusion tends to produce transmural ischemia; a partial or intermittent thrombus may cause NSTEMI or unstable angina. Collateral circulation and preconditioning modify the relationship among anatomy, ECG, and necrosis.
Necrosis progresses from the subendocardium toward the epicardium as occlusion persists. The principle time is muscle is not a slogan, but reflects the progressive loss of salvageable myocardium. The rate varies with location, collateral circulation, demand, previous ischemia, and the microcirculation. Late reperfusion may still prevent extension or complications in selected scenarios, but the greatest benefit is early.

Reperfusion opens the artery but does not guarantee capillary perfusion. Microembolization of thrombus and plaque, endothelial edema, vasoconstriction, radicals, and calcium overload produce microvascular obstruction and no-reflow. Intramyocardial hemorrhage represents severe microcirculatory injury and is associated with a larger infarction and remodeling.
Spontaneous coronary artery dissection causes ACS through an intramural hematoma or separation of the wall that compresses the lumen. It predominantly affects women and may be associated with fibromuscular dysplasia, pregnancy, or stress, without the classic atherosclerotic profile. When the patient is stable and flow is preserved, conservative management is often preferred because PCI may propagate the dissection.

Coronary embolism may originate from atrial fibrillation, prosthetic valves, endocarditis, intracardiac thrombi, a paradoxical shunt, or procedures. Prolonged vasospasm may cause infarction with nonobstructive coronary arteries. Cocaine, amphetamines, and other sympathomimetics increase demand, vasoconstriction, and thrombosis. Vasculitis and coronary anomalies are rarer causes.
Smoking, elevated LDL and apoB, Lp(a), hypertension, diabetes, kidney disease, age, and family history increase risk primarily through atherosclerotic burden and vulnerability. Immediate event risk may be modulated by acute inflammation, sympathetic activation, circadian rhythm, physical or emotional stress, and infections, but there is often no recognizable precipitant.

Some infarctions occur without atherothrombosis. Tachyarrhythmia, anemia, hypoxemia, hypotension, or severe hypertension may cause secondary myocardial infarction; these patients have an unfavorable prognosis because of age and comorbidities, but must not automatically be placed on the same antithrombotic protocol as primary atherothrombotic infarction without assessment of the mechanism.
Coronary occlusion creates a temporal gradient of injury. Diastolic function changes within seconds, followed by regional systolic function, then electrocardiographic changes and pain. Measurable necrosis develops progressively; this sequence explains why an ECG obtained during pain may be diagnostic before troponin and why waiting for the biomarker in evident STEMI is harmful.

Subendocardial vulnerability depends on high wall tension and intramyocardial compression. Tachycardia and hypotension reduce diastolic perfusion and enlarge the infarction. Fever, agitation, and pain increase demand. Analgesia, hemodynamic control, and reperfusion therefore act on different components of the imbalance, but only opening the vessel treats the occlusion.
Systemic inflammation accompanies the event and is necessary to remove necrotic tissue, but an excessive response may extend injury and remodeling. Leukocytosis and C-reactive protein have prognostic but nonspecific value. Selective anti-inflammatory therapy does not replace reperfusion and is not an indiscriminate intervention in the hyperacute phase.

Circadian rhythms influence sympathetic tone, blood pressure, platelet aggregability, and fibrinolysis, contributing to temporal variations in event frequency. Unaccustomed intense exercise, emotional stress, meals, and infections may precipitate ACS in susceptible people. However, the absolute risk from an individual trigger is far lower than that created by atherosclerotic burden and chronic factors.
Pregnancy and the puerperium require particular attention. Spontaneous dissection is an important cause of infarction in young women, especially in the peripartum period, whereas preeclampsia and thrombotic factors modify risk. Radiation, drugs, and delivery timing must be discussed by a multidisciplinary team without delaying a life-saving procedure.

Pathological anatomy, evolution, and acute-event phenotypes

The culprit lesion may be located in any coronary artery, but proximal segments of major arteries have greater consequences because of the subtended myocardial mass. Proximal left anterior descending artery occlusion may cause a large anterior infarction, ventricular dysfunction, and shock; proximal right coronary artery occlusion may involve the right ventricle and atrioventricular node; circumflex occlusion may cause a lateral or posterior infarction with an initially inconspicuous ECG.
The angiographic appearance includes occlusion, irregular stenosis, a filling defect, slow flow, or, after spontaneous lysis, a modest lesion. Thrombosis may already have resolved by the time of coronary angiography. Angiography alone does not always distinguish rupture, erosion, and dissection; OCT and IVUS provide information about the wall and are particularly useful in equivocal presentations or MINOCA.

Epicardial flow is described with the TIMI scale, but TIMI 3 flow does not prove normal tissue perfusion. Myocardial blush, ST-segment resolution, and CMR provide complementary information about the microcirculation. No-reflow may occur despite a well-expanded stent and patent artery.
The STEMI phenotype is defined by the ECG and requires an immediate reperfusion strategy. Not every occlusion produces standard criteria: isolated posterior infarction, the de Winter pattern, bundle branch block with specific signs, and other presentations may represent occlusion equivalents. Interpretation must be clinical and serial.

NSTEMI encompasses a broad spectrum, from small subendocardial necrosis to occlusion of a major vessel without ST-segment elevation. Troponin documents myocardial injury, whereas ECG, GRACE, pain, ventricular function, and instability define invasive timing. Risk is not uniformly lower than in STEMI, particularly over the long term because of age and multivessel disease.
Unstable angina is acute ischemia without detectable acute myocardial injury. With high-sensitivity troponin, many cases historically classified as unstable angina are now NSTEMI. The residual diagnosis requires compatible symptoms, absence of injury, and a context supporting ischemia; it must not become a label for any pain with negative troponin.

Primary myocardial infarction is distinguished from secondary infarction and nonischemic injury. Procedure-related myocardial infarction includes events caused by complications of percutaneous or surgical cardiac procedures within 30 days and is not defined by a fixed troponin threshold. Restenosis, stent thrombosis, or graft failure after 30 days instead falls under primary myocardial infarction. Classification influences treatment and outcome auditing.
MINOCA requires a diagnostic pathway. Early CMR identifies infarction, myocarditis, or Takotsubo syndrome; OCT or IVUS recognizes plaque lesions or occult dissection; testing for vasospasm and the microcirculation is performed when appropriate. Treatment must derive from the cause and not be the same empirical combination for everyone.

Remodeling begins during the first hours. Edema and necrosis alter geometry; over subsequent days, inflammation and degradation make the wall fragile; over weeks, scar and neurohormonal activation determine final volumes. Extensive infarction, microvascular obstruction, and delayed reperfusion increase adverse remodeling.
The Killip classification describes the clinical severity of heart failure in infarction, from absence of congestion to shock. Although historical, it retains prognostic value. The SCAI shock classification defines dynamic stages from risk to extreme shock and facilitates communication and reassessment, but does not replace understanding of the hemodynamic phenotype.

Electrocardiographic localization is approximate. Anterior changes suggest the left anterior descending artery, inferior changes the right or circumflex artery, and lateral changes the circumflex or diagonal branches. Dominance and variants alter correspondence. Reciprocal depression increases the specificity of elevation, whereas a diffuse ECG requires consideration of pericarditis, imbalances, and global ischemia.
Thrombus burden and composition change over time. Very early thrombi may be platelet-rich, whereas organized thrombi contain more fibrin and cells. The coarse distinction between white and red thrombus does not by itself guide therapy, because antiplatelet and anticoagulant drugs act on complementary components of atherothrombosis.

Infarct healing creates a scar whose transmurality and distribution determine function and arrhythmic risk. Reperfusion may salvage a rim of myocardium and reduce dilation. Microvascular obstruction at the center of the territory indicates severe injury, even when the initial ejection fraction appears acceptable.
Multiple infarctions may overlap. An old scar alters the ECG and wall motion and may mask the new event; a new occlusion in an already compromised territory may cause shock with a troponin increase that is not proportionally large. Serial assessment and comparison with previous imaging are particularly important.

Clinical manifestations

The classic symptom is sudden, pressing, constricting, or heavy chest discomfort, often retrosternal and radiating to one or both arms, shoulders, jaw, neck, back, or epigastrium. It generally lasts more than a few minutes, may recur, and does not resolve completely with rest. Intensity and description do not distinguish STEMI, NSTEMI, and unstable angina.
Dyspnea, sweating, nausea, vomiting, weakness, agitation, and syncope may accompany pain or be the dominant presentation. Older people, people with diabetes, women, and patients with kidney failure more often have paucisymptomatic presentations, but no group is free from classic pain. The absence of pain increases the risk of delay.

An inferior infarction may cause nausea, vomiting, and bradycardia through vagal activation. Right ventricular involvement causes hypotension, jugular venous distension, and relatively clear lungs; indiscriminate administration of nitrates or diuretics may worsen preload dependence. A posterior infarction may present with ST-segment depression in V1-V3 and requires posterior leads.
An extensive anterior infarction may cause tachycardia, a third heart sound, crackles, hypotension, and shock. A new systolic murmur suggests mitral regurgitation or a septal defect, but in shock the gradient may be insufficient to generate a loud murmur. Pleuritic pain in the following days may indicate pericarditis.

Cardiac arrest may be the first manifestation. Shockable rhythms are frequent in the early stages; hypoxia, shock, and extensive necrosis favor pulseless electrical activity or asystole. After return of spontaneous circulation, the ECG and clinical presentation guide coronary angiography, avoiding automatic attribution of every arrest to coronary artery disease.
Hemodynamic instability manifests as hypotension, cold skin, confusion, oliguria, and elevated lactate. Shock may be predominantly left ventricular, right ventricular, mechanical, or mixed. Echocardiography and selective catheterization define the phenotype and prevent uniform treatment of physiologically different conditions.

In NSTE-ACS, recurrent pain despite treatment, dynamic ST-segment changes, life-threatening arrhythmias, acute heart failure, or shock indicates very high risk. Age, troponin, creatinine, heart rate, blood pressure, and cardiac arrest are incorporated into the GRACE score. Ischemic risk must be assessed together with bleeding risk.
Physical examination must begin with airway, breathing, circulation, neurological status, and oxygen saturation. Signs of heart failure, hypoperfusion, valvular disease, mechanical complications, and alternative diagnoses are sought. Pulse asymmetry, neurological deficits, or migrating pain raises suspicion of aortic dissection, in which anticoagulation and thrombolysis may be catastrophic.

The urgent differential diagnosis includes aortic dissection, pulmonary embolism, pneumothorax, tamponade, myocarditis, and pericarditis. Takotsubo syndrome may mimic STEMI or NSTEMI with troponin elevation and regional dysfunction. Gastrointestinal and musculoskeletal disorders are common, but must be reasoned conclusions rather than shortcuts in the face of a nondiagnostic ECG.
The history must document the exact time of onset, progression, medications, anticoagulants, previous bleeding, stroke, procedures, kidney function, allergies, and substance use. Time of onset determines eligibility for fibrinolysis and interpretation of troponin; bleeding risk influences access, doses, and antithrombotic duration.

Older patients may present with delirium, a fall, syncope, or heart failure without pain. Frailty and comorbidities increase bleeding and procedural risk, but chronological age alone does not justify withholding revascularization. Benefit, life expectancy, functional status, and preferences must be assessed explicitly.
In diabetes, neuropathy and autonomic dysfunction reduce perception; diffuse and microvascular disease increase burden. In kidney failure, troponin may be chronically elevated, but a dynamic change with ischemia remains significant. Concern about contrast must not delay urgent coronary angiography when ischemic risk is high.

Pain that resolves before assessment may correspond to spontaneous reperfusion. Normalization of the ECG does not make the presentation benign because the thrombus may reform. Dynamic changes documented by prehospital services or previous devices are valuable and must accompany the patient.
Recurrence after PCI may result from stent thrombosis, dissection, no-reflow, spasm, or nonischemic pain. New ST-segment elevation and instability require immediate reassessment. Persistence of mild pressure after a procedure alone does not permit distinction among causes without ECG, echocardiography, and the angiographic context.

Investigations and diagnosis

The ECG must be obtained and interpreted within approximately ten minutes of first medical contact in patients with suspected ACS. A nondiagnostic tracing must be repeated, ideally during symptoms. Comparison with previous ECGs is useful but must not delay reperfusion. Continuous monitoring identifies arrhythmias and dynamic changes.

Conventional electrocardiographic criteria for ST-segment elevation at the J point, in the absence of left ventricular hypertrophy or left bundle branch block

• New ST-segment elevation in at least two contiguous leads.
• In all leads except V2-V3: elevation of at least 1 mm.
• In V2-V3: at least 2.5 mm in men younger than 40 years, at least 2 mm in men aged 40 years or older, and at least 1.5 mm in women.

Standard criteria do not encompass all occlusions. Leads V7-V9 assess posterior infarction and V3R-V4R right ventricular infarction. The de Winter pattern, localized hyperacute changes, and modified Sgarbossa criteria in left bundle branch block or pacing may indicate occlusion. The presence of new bundle branch block alone is not an automatic criterion.
High-sensitivity troponin must be measured on arrival and repeated using validated 0/1-hour or 0/2-hour algorithms when appropriate. The initial value and absolute change depend on the assay. A result in the rule-out pathway is valid only together with time from symptoms, ECG, and the clinical presentation; very early pain or high risk requires caution.

Criteria from the Fifth Universal Definition of Acute Myocardial Infarction

• Rise 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 of acute coronary pathology; or new or presumed new loss of viable myocardium or a regional abnormality with an ischemic pattern.

Complete blood count, creatinine, electrolytes, glucose, coagulation tests, and a lipid profile complete the assessment. An early lipid sample is useful because LDL may decrease after the event. BNP or NT-proBNP has prognostic value but does not diagnose ACS. D-dimer and other tests are used only when required by the differential diagnosis.
Urgent echocardiography assesses regional abnormalities, ventricular function, the right ventricle, and complications, but must not delay transfer to the catheterization laboratory in evident STEMI. It is essential in shock, suspected rupture or mitral regurgitation, and when the ECG is uncertain. The absence of an abnormality does not exclude a small NSTEMI.

CCTA may exclude coronary artery disease in selected low- or intermediate-risk patients with nondiagnostic ECG and troponin, but is not the first-choice test when probability and risk are high. CMR defines necrosis, edema, microvascular obstruction, and alternative diagnoses, particularly in MINOCA or discordant presentations.
Coronary angiography is both diagnostic and therapeutic. Radial access reduces bleeding and mortality compared with femoral access in many ACS populations when performed by experienced operators. Assessment identifies the culprit lesion, flow, thrombus, and multivessel disease. Physiology of nonculprit lesions during the acute phase requires careful interpretation.

OCT may show rupture, an intact cap with thrombus, dissection, malapposition, or stent thrombosis; IVUS penetrates more deeply and defines dimensions and burden. Imaging is useful when mechanisms are uncertain and optimizes complex PCI. In the presence of massive thrombus, OCT may be limited and requires contrast.
GRACE stratification is recommended in NSTE-ACS to estimate mortality and support invasive timing. Bleeding risk may be estimated with ARC-HBR, PRECISE-DAPT, or other tools, but no score replaces clinical judgment, changes over time, and factors not included.

In MINOCA, the final diagnosis requires exclusion of extracardiac and nonischemic causes of troponin elevation. Ideally early CMR, intracoronary imaging, and selected vasomotor testing increase diagnostic yield. Thrombophilia, an embolic source, and dissection are investigated according to context, not with indiscriminate panels.
Chest radiography does not diagnose ACS but may show edema, cardiomegaly, pneumothorax, or a widened mediastinum. It must not delay reperfusion in STEMI. Aortic or pulmonary CT is indicated when dissection or embolism is plausible and the patient is sufficiently stable for the pathway.

The troponin delta must be interpreted with assay-specific units. Relative percentages are less reliable near the limit, whereas absolute changes are often preferred in algorithms. Hemolysis, heterophile antibodies, macrotroponin, and interference are rare but must be considered when the result remains discordant with every clinical element.
The GRACE score uses age, heart rate, blood pressure, creatinine, Killip class, cardiac arrest, ST-segment deviation, and biomarkers. Its usefulness is greatest when calculated correctly and updated with reliable data. A low score does not negate a very-high-risk feature such as refractory pain or instability.

Bleeding risk is dynamic. Hemoglobin, platelets, glomerular filtration, age, bleeding history, cancer, and anticoagulation must be documented before the procedure when time permits. Identifying risk serves to choose access, doses, and duration, not to indiscriminately withhold effective treatments.
In shock, lactate, liver and kidney function, venous saturation, and echocardiographic parameters track perfusion and response. A pulmonary artery catheter may be useful in complex or refractory shock at experienced centers. No single value defines the phenotype, and repeated reassessment is necessary.

Treatment and prognosis

Treatment begins within the emergency system. Monitoring, venous access, an available defibrillator, and transfer to an appropriate network are priorities. Oxygen is indicated in hypoxemia, particularly with saturation below 90%, and is not routinely recommended in normoxemic patients. Opioids may reduce severe pain but delay absorption of oral antiplatelet drugs and must be used judiciously.
Aspirin is given early unless contraindicated. A P2Y12 inhibitor is selected according to the invasive strategy, bleeding risk, age, previous stroke, anticoagulation, and anatomy. Ticagrelor or prasugrel is preferred to clopidogrel in many patients with ACS undergoing PCI; prasugrel is contraindicated after stroke or TIA, and pretreatment before anatomy is known is not universal.

Parenteral anticoagulation reduces thrombus propagation. Unfractionated heparin, enoxaparin, fondaparinux, and bivalirudin have different roles according to STEMI, NSTE-ACS, the invasive strategy, kidney function, and bleeding risk. Fondaparinux must not be used as the sole anticoagulant during PCI because of the risk of catheter thrombosis.
Sublingual or intravenous nitrates may relieve pain and hypertension, but do not improve survival and are contraindicated in hypotension, suspected right ventricular infarction, recent use of PDE5 inhibitors, and some obstructive conditions. Early beta-blockers are avoided in shock, acute heart failure, bradycardia, or risk of shock; they are used when hemodynamically appropriate.

In STEMI, primary PCI is preferred if the artery can be opened within recommended times. If the delay from diagnosis to PCI exceeds 120 minutes and onset was within twelve hours, fibrinolysis should be given rapidly in the absence of contraindications, ideally within ten minutes of diagnosis, followed by immediate transfer. Failed reperfusion requires rescue PCI.
Fibrinolysis is contraindicated with previous intracranial hemorrhage, recent ischemic stroke, intracranial neoplasm or vascular malformation, suspected aortic dissection, active bleeding, and other high-risk conditions. Age, severe hypertension, anticoagulation, and recent procedures require specific assessment. PCI is preferred when available and in shock.

In NSTE-ACS, hemodynamic instability, shock, refractory recurrent pain, life-threatening arrhythmias, or a mechanical complication requires an immediate strategy. In high-risk patients, including those with confirmed NSTEMI and a high GRACE score, coronary angiography is performed during hospitalization with priority defined by the profile. An indiscriminately immediate strategy is not necessary in every stable NSTEMI.
PCI aims to restore flow and obtain a well-expanded and apposed stent. Radial access and intracoronary imaging in complex lesions improve safety and quality. Routine thrombus aspiration is not recommended, but may be used as bailout for selected thrombus. Preparation of calcified lesions may require dedicated techniques.

In hemodynamically stable patients with STEMI and multivessel disease, complete revascularization of significant nonculprit lesions, during the procedure or in a staged manner, reduces new events compared with treatment of the culprit lesion alone. In cardiogenic shock, by contrast, immediate multivessel PCI increases risk compared with an initial culprit-only strategy, and the other lesions are reassessed after stabilization.
Urgent CABG is indicated when anatomy cannot be treated with PCI, mechanical complications are present, or persistent ischemia involves a large area at risk. Timing must consider antiplatelet therapy and bleeding, but instability does not permit arbitrary delay. The Heart Team is useful in complex anatomy when clinical time allows.

The default duration of dual antiplatelet therapy is twelve months, but it is not rigid. Abbreviated strategies with transition to P2Y12 monotherapy reduce bleeding in selected patients; de-escalation may be guided or clinical; extended treatment may be considered with high ischemic and low bleeding risk. In patients requiring an oral anticoagulant, triple therapy is maintained for as short a time as possible.
Intensive lipid-lowering therapy must begin during hospitalization. A high-intensity statin is combined early with ezetimibe if the target is unlikely to be reached, with addition of an anti-PCSK9 agent or other therapies according to LDL, risk, and response. Assessment at four to eight weeks permits rapid correction, avoiding months of residual exposure.

ACE inhibitors or ARBs, beta-blockers, and mineralocorticoid receptor antagonists are prescribed according to ejection fraction, heart failure, diabetes, blood pressure, and other indications. SGLT2 inhibitors are part of appropriate heart-failure treatment but are not an acute antithrombotic therapy. Glycemic management avoids both severe hyperglycemia and hypoglycemia.
Cardiac rehabilitation must begin early and includes exercise, education, nutrition, smoking cessation, psychological support, return to work, and adherence. Before discharge, warning signs, nitrate use, the importance of not interrupting DAPT, and the follow-up plan are explained.

In-hospital prognosis depends mainly on shock, arrest, age, ventricular function, creatinine, and infarct extent. In the long term, multivessel disease, diabetes, kidney function, bleeding, adherence, and lipid control matter. NSTEMI may have late mortality similar to or higher than STEMI because of age and comorbidities, despite often lower initial mortality.
P2Y12 pretreatment in NSTE-ACS before anatomy is known may increase bleeding and delay CABG without certain benefit for everyone. The decision depends on the drug and expected delay. In STEMI intended for PCI, early administration is instead part of the usual strategy, taking vomiting, shock, and delayed absorption into account.

Glycoprotein IIb/IIIa inhibitors are not routinely used before coronary angiography, but may be used as bailout for a large thrombus, no-reflow, or a thrombotic complication. Bleeding risk and kidney function guide selection and dose. Their additional effect is smaller in the era of potent P2Y12 inhibitors and radial access.
Contemporary drug-eluting stents are preferred. Preparation, sizing, and optimization are more important than implantation alone. Left main lesions, bifurcations, small vessels, calcium, and thrombosis require dedicated strategies. A stent must not be implanted in stable spontaneous dissection merely to make the vessel angiographically regular.

During fibrinolysis, ST-segment resolution, pain relief, and reperfusion arrhythmias suggest efficacy, but coronary angiography remains necessary. Insufficient ST-segment reduction or instability requires rescue PCI. Even after apparent success, a pharmacoinvasive strategy is adopted with transfer and angiography within recommended times.
Management of shock requires vasopressors and inotropes at the lowest effective intensity, treatment of hypoxemia, and reperfusion. Norepinephrine is generally preferred to more arrhythmogenic drugs for supporting blood pressure, whereas the inotropic agent depends on hemodynamics. Mechanical support is selected according to phenotype, reversibility, and center expertise, not applied automatically.

After cardiac arrest, priorities include airway control, cerebral perfusion, temperature management according to protocols, and treatment of the cause. Persistent ST-segment elevation supports immediate coronary angiography; in the absence of elevation, immediate angiography is not automatic for everyone and depends on instability and coronary probability.
Ejection fraction must be measured before discharge. In patients with reduced function, treatment is optimized and function reassessed after the period needed for recovery before deciding on a primary-prevention defibrillator. Late arrhythmias, syncope, and an extensive scar may require earlier specialist assessment.

Return to activity, driving, work, and sexual activity depends on infarct extent, revascularization, function, and regulations. Clear counseling reduces inactivity and anxiety. Depression and post-traumatic stress are common after ACS and affect adherence and prognosis, and therefore must be recognized and treated.

Complications

Early ventricular arrhythmias result from ischemia and may cause sudden death. Ventricular fibrillation within the first 48 hours does not automatically imply the same late risk as an arrhythmia occurring after the acute phase. A mature scar may sustain ventricular tachycardia and requires stratification after recovery.
Bradycardia and atrioventricular block are frequent in inferior infarction and often transient; infranodal blocks in anterior infarction suggest extensive injury. Temporary pacing is reserved for symptomatic bradycardia or high-risk block, not for a stable electrocardiographic abnormality alone.

Acute heart failure ranges from mild congestion to shock. Cardiogenic shock is a syndrome of hypoperfusion with high mortality, not defined by blood pressure alone. Culprit-vessel reperfusion, respiratory support, and vasoactive therapy are tailored to the phenotype. Mechanical devices do not have a universal routine indication and are selected by experienced teams.
Free-wall rupture causes hemopericardium and tamponade, a septal defect causes an acute shunt, and papillary muscle rupture causes severe mitral regurgitation. Sudden deterioration, a new murmur, or pulmonary edema requires immediate echocardiography. Stabilization is a bridge to surgical or, in selected cases, percutaneous correction, not definitive treatment.

Right ventricular infarction causes hypotension and systemic congestion and may require cautious optimization of preload. Biventricular involvement worsens prognosis. Excessive fluid administration may dilate the right ventricle, shift the septum, and worsen left-sided output.
Microvascular obstruction and no-reflow increase infarct size and remodeling. No single treatment can prevent them in every patient. Prevention of delay, accurate PCI technique, limitation of microembolization, and selective treatment of vasoconstriction are components of management.

Early pericarditis, Dressler syndrome, true aneurysm, and pseudoaneurysm are temporally distinct complications. Post-infarction pain must be distinguished from reinfarction, stent thrombosis, and dissection. ECG, troponin, echocardiography, and temporal context provide guidance.
Left ventricular thrombus occurs mainly after a large anterior infarction with apical akinesia and may embolize. Contrast echocardiography and CMR improve diagnosis. Anticoagulation must be balanced against the need for antiplatelet therapy, its duration, and follow-up imaging.

Major bleeding is a prognostic complication of treatment. Radial access, correct dosing for weight and kidney function, proton-pump inhibitors in patients at gastrointestinal risk, and reduction of triple therapy limit harm. Transfusion is not automatic at a single threshold and must consider ischemia, symptoms, and stability.
Stent thrombosis may cause catastrophic reinfarction; factors include interruption of antiplatelet therapy, underexpansion, malapposition, and high thrombogenicity. Restenosis more often causes late recurrent ischemia. IVUS or OCT helps identify the mechanism and guide correction.

Remodeling, mitral regurgitation, heart failure, and ischemic cardiomyopathy are chronic consequences. Recurrent infarction and progression of nonculprit plaques add scar. Intensive secondary prevention is therefore part of treatment of the first event from the time of hospitalization.
Free-wall rupture may be immediately fatal or present as a contained subacute rupture with effusion and intermittent instability. Pericardiocentesis may be a bridging measure in tamponade, but correction is surgical. Anticoagulation and thrombolysis may aggravate hemorrhage, making recognition essential.

A post-infarction septal defect causes a rapid left-to-right shunt, right ventricular overload, and low output. Doppler echocardiography defines location and severity. Stabilization with support and surgical or percutaneous closure requires a Heart Team; timing balances tissue fragility against instability.
Papillary muscle rupture, most often posteromedial because of its single blood supply, causes acute mitral regurgitation, pulmonary edema, and shock. The ventricle may not be dilated and the ejection fraction may appear normal or hyperdynamic. Hemodynamic severity must therefore not be underestimated because of a preserved ejection fraction.

A true ventricular aneurysm consists of scar and is associated with heart failure, arrhythmias, and thrombus; a pseudoaneurysm is a rupture contained by pericardium or adhesions and has a higher risk of rupture. CT and CMR complement echocardiography when the neck and wall are not defined.
Infections, kidney injury, delirium, and deconditioning particularly complicate the course of older people and intensive-care patients. Safe early mobilization, prevention of iatrogenic injury, and daily review of catheters and sedation are part of the overall cardiovascular outcome.