Giới thiệu
Myocardial infarction (MI) is death of cardiac myocytes (irreversible
necrosis) caused by prolonged or severe myocardial ischemia from insufficient or absent coronary blood flow and
reperfusion injury. It is important to distinguish myocardial injury
from MI. Myocardial injury may result from ischemic or non-ischemic causes,
whereas MI is myocardial injury caused by prolonged ischemia and resulting in
myocardial cell death. The term “acute” usually refers to the time 6 hours to 7
days following the pathologic appearance of the infarct. A recurrent MI is an
MI occurring 28 days after an incident MI, while a reinfarction is an acute MI
occurring within 28 days of an incident or recurrent MI.
Acute coronary syndrome (ACS) is any constellation of symptoms compatible
with acute myocardial ischemia, usually caused by sudden reduction in coronary
blood flow from atherosclerotic plaque rupture or erosion and subsequent
thrombosis.
Dịch tễ học
Cardiovascular disease (CVD) remains
the number one cause of mortality in Western countries, with acute coronary
disease being the leading cause. MI with ST-segment elevation constitutes
approximately 25% of ACS.
The incidence rate of MI among Asians was lower than
other races. The reason for this may be due to lower prevalence of major risk
factors (eg hypertension, smoking, obesity) among Asian people. In Asian
countries such as Japan and Korea, the incidence rate is higher in men than in
women.
Sinh lý bệnh
The initial mechanism in acute MI is the rupture of vulnerable, lipid-laden atherosclerotic coronary plaque, resulting in a highly thrombogenic plaque core and matrix material circulation in the blood. Platelets then activate and aggregate at the site of the injury. Thrombin is generated, which accelerates platelet activation, resulting in fibrin trapping of red blood cells and leading to thrombus formation. A totally occluding thrombus leads to ST-elevation MI. Reduced blood flow results in ischemia, leading to myocardial cell injury/death, ventricular dysfunction, and cardiac arrhythmias. Myocardial necrosis begins 20 minutes after coronary occlusion.
Nguyên nhân
The etiologies of MI are:
- Coronary artery spasm
- Coronary atherosclerosis and plaque rupture
- Coronary embolism from atrial fibrillation, rheumatic heart disease, infective endocarditis, or intracavitary thrombus
- Dissection into coronary arteries (aneurysmal, iatrogenic or spontaneous)
- Periarteritis and other coronary artery inflammatory diseases
- Anomalous origin of coronary artery (eg interarterial [aorta and pulmonary artery] course of coronary artery)
- Increased blood viscosity or hypercoagulable states (eg polycythemia vera, systemic lupus, antiphospholipid syndrome)
- MI with normal coronaries frequently seen in younger patients and cocaine users
- Chest pain post-ST-segment elevation MI (STEMI) may be due to reinfarction or recurrent MI, myocardial ischemia (angina), pericarditis or non-cardiac causes
Yếu tố nguy cơ
The
risk factors for STEMI are:
- Age
- Sex
- Family history of heart disease
- Modifiable
risk factors include:
- Hyperlipidemia
- Hypertension
- Diabetes
- Chronic kidney disease (CKD)
- Obesity
- Psychosocial factors (eg stress)
- Lifestyle
risk factors include:
- Smoking
- Diet
- Lack of exercise
- Alcohol intake
Phân loại
An acute MI (AMI) is classified clinically as:
- Primary MI: Spontaneous onset of symptoms or signs of acute myocardial
ischemia and injury without an alternative acute condition or cardiac procedure
triggering the presentation
- Diagnosis is confirmed and etiology is defined if atherothrombosis or an alternative acute coronary pathology is identified, including spontaneous coronary artery dissection, coronary embolism, vasospasm, and restenosis, stent thrombosis or bypass graft failure occurring >30 days from procedure
- When coronary angiography or cardiac imaging is unavailable or unsuitable, primary MI may be diagnosed using the combined assessment of biomarkers, electrocardiographic findings and clinical criteria, without requiring additional confirmatory features
- Secondary MI: Acute myocardial ischemia and injury secondary to an
alternative acute condition resulting in myocardial oxygen supply-demand
mismatch (ie increased demand [eg tachycardia or severe hypertension] and/or
reduced supply [eg anemia, hypoxia, hypotension])
- Diagnosis is confirmed if ischemia is a result of obstructive coronary artery disease (CAD) (≥70% stenosis in an epicardial vessel by angiography or ≥50% stenosis that is flow-limiting on physiological assessment) without acute coronary pathology, or myocardial injury results in a new or presumed new regional wall motion abnormality or absence of viable myocardium
- Procedure-related MI: Acute myocardial ischemia and injury occur due to
a coronary complication occurring within 30 days of a percutaneous or surgical
cardiac procedure
- Diagnosis is more likely immediately after a procedure when cardiac biomarker levels exceed preprocedural values and continue to rise at 6 hours (eg >5 times the upper reference limit [URL] following an intervention) and at 24 hours (eg >35 times URL following surgery)
- Diagnosis is confirmed if there is angiographic evidence of a coronary complication of percutaneous intervention or cardiac surgery, or myocardial injury results in a new or presumed new regional wall motion abnormality or absence of viable myocardium
- Both a complication and a new or presumed new regional wall motion abnormality or absence of viable myocardium are required when the complication arises during the index procedure, or the procedure is performed in the management of AMI
- Where MI is the likely cause of death, clinical classification (primary, secondary or procedure-related) should be applied based on setting or post-mortem findings
Myocardial injury with non-obstructive coronary arteries (MINOCA) is a
working diagnosis in patients with clinical features of possible MI with no
significant coronary artery stenosis (ie <50%) on coronary angiography and
includes non-coronary cardiac (eg myocarditis, Takotsubo syndrome,
cardiomyopathy) or non-cardiac (eg pulmonary embolism) causes.
A
prior or unrecognized/silent MI is a condition that has the
following criteria:
- Abnormal Q waves with or without symptoms in the absence of non-ischemic causes
- Loss of viable myocardium on imaging (preferably with cardiac magnetic resonance [CMR] with late gadolinium enhancement) consistent with an ischemic cause
- Patho-anatomical findings of a previous MI