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ACUTE MYOCARDIAL INFARCTION: PATHOPHYSIOLOGY, CLINICAL
FEATURES, AND CONTEMPORARY MANAGEMENT
Axmadulina Galiya Marsovna
Abstract:
Acute myocardial infarction (AMI) arises from sudden occlusion of a coronary artery,
most often following atherosclerotic plaque rupture and superimposed thrombus formation.
Within minutes of vessel closure, downstream myocardium experiences ischemic necrosis that, if
not promptly reperfused, leads to irreversible injury and loss of contractile function. Clinically,
AMI manifests as prolonged chest discomfort – often crushing or constricting – accompanied by
diaphoresis, dyspnea, and autonomic features. Electrocardiography differentiates ST-elevation
from non-ST-elevation infarctions, while troponin assays confirm myocardial necrosis. Imaging
modalities, including echocardiography, cardiac magnetic resonance, and coronary angiography,
further delineate infarct extent, guide revascularization decisions, and assess left ventricular
function. Early reperfusion via primary percutaneous coronary intervention or fibrinolysis,
combined with antiplatelet, anticoagulant, beta-blocker, statin, and renin-angiotensin system
inhibitor therapy, markedly reduces infarct size and improves survival. Post-AMI care focuses on
prevention of recurrent events through lifestyle modification, pharmacotherapy, and structured
cardiac rehabilitation. This review synthesizes current understanding of AMI pathophysiology,
clinical presentation, diagnostic strategies, and evidence-based management to optimize patient
outcomes.
Keywords
: Acute myocardial infarction; Atherosclerotic plaque rupture; ST-elevation
myocardial infarction; Percutaneous coronary intervention; Cardiac rehabilitation
Myocardial infarction occurs when an atherosclerotic plaque within a coronary artery ruptures or
erodes, triggering the rapid formation of a thrombus that abruptly occludes blood flow. This
sudden obstruction deprives downstream myocardium of oxygen and nutrients, leading to
ischemic necrosis within minutes. Although collateral vessels can sometimes provide partial
perfusion, they rarely compensate fully in the acute setting, and irreversible myocardial injury
begins as early as twenty to thirty minutes after occlusion.
Clinically, patients with myocardial infarction often describe a prolonged, severe chest
discomfort, distinguishing it from the transient pain of angina. The sensation may be described as
crushing, constricting, or burning, typically located retrosternally but possibly radiating to the
neck, jaw, left arm, or back. Accompanying symptoms frequently include profuse sweating,
nausea, vomiting, dyspnea, and a sense of impending doom. In some individuals- particularly the
elderly, women, and those with diabetes - symptoms may be atypical or muted, manifesting as
unexplained fatigue, indigestion, or shortness of breath without significant chest pain.
Electrocardiographic changes are central to diagnosing MI. In ST-elevation myocardial
infarction, persistent ST-segment elevation appears in leads corresponding to the infarcted
territory, often accompanied by reciprocal ST depression in opposing leads. Pathological Q
waves may develop within hours to days, reflecting transmural necrosis. In non-ST-elevation
myocardial infarction, ST depression or T-wave inversion is seen without persistent ST elevation;
biomarkers confirm necrosis. Cardiac troponins- now the gold standard- rise within three to six
hours, peak at around twenty-four hours, and remain elevated for up to two weeks. Creatine
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kinase-MB isoenzyme provides additional corroboration but lacks the sensitivity and specificity
of troponin.
Beyond ECG and biomarkers, imaging plays an important role. Echocardiography reveals
regional wall motion abnormalities, which correspond to areas of infarction and can help
distinguish MI from other causes of chest pain. Cardiac magnetic resonance imaging offers
detailed tissue characterization, identifying edema, necrosis, and scar formation. Coronary
angiography confirms the location and extent of occlusion, guides revascularization, and assesses
the need for stenting or bypass surgery.
Immediate management focuses on restoring perfusion to minimize infarct size and preserve left
ventricular function. Reperfusion is achieved either pharmacologically- using fibrinolytic agents
to dissolve the thrombus- or mechanically via primary percutaneous coronary intervention (PCI).
When performed promptly, PCI offers superior outcomes, reducing mortality and the risk of
complications. Adjunctive therapies include dual antiplatelet therapy (aspirin plus a P2Y₁₂
inhibitor), anticoagulation (e.g., heparin), and high-intensity statins to stabilize plaques and
reduce inflammation. Beta-blockers decrease myocardial oxygen demand by slowing heart rate
and reducing contractility, while ACE inhibitors or angiotensin receptor blockers mitigate
remodeling and heart failure risk.
Complications span electrical, mechanical, and inflammatory domains. Ventricular arrhythmias-
such as ventricular tachycardia and fibrillation- occur most commonly in the early hours and
often cause sudden cardiac death. Heart block may result from ischemia of the conduction
system, particularly in inferior infarctions. Mechanical complications, though less frequent in the
era of rapid reperfusion, remain serious: papillary muscle rupture leads to acute severe mitral
regurgitation and pulmonary edema; ventricular septal rupture causes a left-to-right shunt with
hemodynamic collapse; free wall rupture precipitates tamponade. Myocardial inflammation can
give rise to pericarditis, presenting days after the infarction.
Long-term care focuses on preventing recurrent events and managing heart failure. Cardiac
rehabilitation- including supervised exercise, dietary counseling, and smoking cessation-
improves functional capacity and quality of life. Optimizing medical therapy with ACE
inhibitors, beta-blockers, statins, and antiplatelet agents reduces the risk of reinfarction and death.
Patients undergo periodic assessment of left ventricular function, often with echocardiography,
to guide decisions about implantable cardioverter-defibrillators in those with severely reduced
ejection fraction.
Myocardial infarction represents the most severe manifestation of ischemic heart disease, marked
by abrupt coronary occlusion, irreversible myocardial necrosis, and a spectrum of acute and
chronic complications. Rapid recognition, prompt reperfusion, and comprehensive secondary
prevention are essential to limit myocardial damage, avert life-threatening events, and improve
long-term outcomes.
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