- Myocardial infarction, or heart attack, occurs when blood flow to the heart is blocked, often by plaque build-up.
- Common symptoms include chest pain, shortness of breath,
and nausea, but they can vary, especially in women and the elderly.
- Risk factors include smoking, high blood pressure, and
family history, among others.
- The evidence leans toward immediate treatment with aspirin
and procedures like angioplasty to restore blood flow.
*Definition -
Myocardial infarction, commonly known as a heart attack,
happens when the blood supply to part of the heart is severely reduced or
blocked, usually due to plaque (cholesterol-containing deposits) in the
coronary arteries. This blockage can lead to heart muscle damage or death if
not treated promptly.
*Symptoms -
Symptoms often include chest pain or discomfort, which may
feel like pressure, tightness, or squeezing, and can radiate to the shoulder,
arm, back, neck, jaw, or upper belly. Other signs include shortness of breath,
cold sweat, fatigue, nausea, vomiting, and lightheadedness. Some people,
especially women and the elderly, may have atypical symptoms like neck or arm
pain, or even silent heart attacks with no noticeable symptoms.
*Causes and Risk Factors -
The main cause is coronary artery disease, where plaque build-up
narrows arteries, potentially leading to a complete blockage if a plaque
ruptures and forms a clot. Other causes include coronary artery spasms,
infections like COVID-19, and spontaneous coronary artery dissection. Risk
factors include age (men ≥45, women ≥55), smoking, high blood pressure, high
cholesterol, diabetes, obesity, family history, sedentary lifestyle, unhealthy
diet, stress, and conditions like preeclampsia or autoimmune diseases.
*Diagnosis and Treatment -
Diagnosis typically involves an ECG to detect heart muscle
damage and blood tests for cardiac biomarkers like troponin. Treatment is
urgent, often starting with aspirin to prevent further clotting and
nitroglycerin for pain relief. Procedures like percutaneous coronary
intervention (PCI) or thrombolysis are used to restore blood flow, especially
within the first few hours. Long-term management includes medications like
beta-blockers and statins, plus lifestyle changes.
*Prevention -
Preventing heart attacks involves a heart-healthy lifestyle:
regular exercise (e.g., 150 minutes of moderate activity weekly), a diet low in
saturated fats and salt, quitting smoking, and managing conditions like
hypertension. Medications like statins may be recommended, and learning CPR can
be lifesaving in emergencies.
*Comprehensive Overview of Myocardial Infarction -
Myocardial infarction, commonly referred to as a heart
attack, is a critical medical condition characterized by the sudden blockage of
blood flow to a portion of the heart muscle, leading to tissue death due to
oxygen deprivation. This condition is a leading cause of death globally, with
significant implications for public health and individual well-being. The
following sections provide a detailed examination of its definition, symptoms,
causes, risk factors, diagnosis, treatment, and prevention strategies, drawing
from authoritative sources to ensure accuracy and depth.
*Definition and Classification -
Myocardial infarction (MI) occurs when the flow of blood to
the heart is severely reduced or blocked, typically due to plaque build-up
(atherosclerosis) in the coronary arteries, which can rupture and form a clot,
causing complete or partial obstruction. It is classified into two main types
based on electrocardiogram (ECG) findings:
- **ST Elevation Myocardial Infarction (STEMI)**: Involves
acute, complete blockage of a medium or large coronary artery, accounting for
25–40% of MIs.
- **Non-ST Elevation Myocardial Infarction
(NSTEMI)**: Involves partial blockage, sometimes with total occlusion of
smaller arteries.
This classification is crucial for determining treatment
urgency and approach.
*Symptoms and Presentation -
The symptoms of MI can vary widely, affecting recognition and
timely intervention. Common manifestations include:
- Chest pain or discomfort, often described as pressure,
tightness, squeezing, or aching, typically retrosternal and radiating to the
left shoulder, arm, or jaw.
- Pain spreading to the shoulder, arm, back, neck, jaw,
teeth, or upper belly, sometimes mimicking heartburn.
- Shortness of breath, nausea, vomiting, cold sweat, fatigue,
and lightheadedness or sudden dizziness.
Atypical presentations are notable, particularly in women,
the elderly, and diabetics, who may experience:
- Neck pain, arm pain, or fatigue instead of chest pain.
- Silent MIs, representing 22–64% of all infarctions, more
common in the elderly and those with diabetes, where symptoms are minimal or
absent.
Warning signs may precede the event by hours, days, or weeks,
such as recurring angina (chest pain or pressure not relieved by rest),
highlighting the importance of awareness.
*Causes and Underlying Mechanisms -
The primary cause of MI is coronary artery disease (CAD),
characterized by the accumulation of atherosclerotic plaque in the coronary
arteries. This plaque, composed of cholesterol, cellular waste, and other
substances, can rupture, leading to thrombus formation and total occlusion of
the artery. Less common causes include:
- Coronary artery spasms, potentially triggered by cocaine
use, significant emotional stress (e.g., Takotsubo syndrome), or extreme cold.
- Certain infections, such as COVID-19, which may contribute
to vascular inflammation.
- Spontaneous coronary artery dissection (SCAD), more
prevalent in women and associated with pregnancy or connective tissue
disorders.
*Risk Factors and Epidemiology -
Numerous risk factors contribute to the likelihood of
experiencing an MI, categorized as modifiable and non-modifiable:
- **Non-Modifiable**: Age (men
≥45, women ≥55), male sex, family history of early heart attack (before age 55
for males, 65 for females).
- **Modifiable**: Smoking (causing 36% of CAD
cases), high blood pressure, high cholesterol or triglycerides, diabetes,
obesity (20% contribution), sedentary lifestyle (7–12% contribution), unhealthy
diet (high in sugars, animal fats, processed foods, trans fats, salt),
excessive alcohol intake, stress, and illegal drug use (e.g., cocaine,
amphetamines).
- **Additional Factors**: Shift work,
combined oral contraceptive pills, non-steroidal anti-inflammatory drugs,
endometriosis under 40, air pollution, infections (e.g., Chlamydophila
pneumoniae, influenza), Kawasaki disease, high homocysteine levels, and
genetics (27 genetic variants, strongest association with chromosome 9p21,
genes like PCSK9, SORT1, CDKN2A/2B).
*Diagnosis: Methods and Criteria -
Diagnosing MI involves a combination of clinical assessment,
imaging, and laboratory tests to confirm myocardial damage:
- **Electrocardiogram (ECG)**: Detects
changes such as ST elevation, T wave inversion, new Q waves, or left bundle
branch block, crucial for classifying STEMI versus NSTEMI.
- **Blood Tests**: Measure cardiac biomarkers,
with troponin preferred due to its specificity (rises within 2–3 hours, peaks
in 1–2 days), and CK-MB as an alternative, though less specific.
- **Coronary Angiography**: Provides
visualization of blockages, guiding intervention strategies.
- **Diagnostic Criteria**: Defined by
elevated cardiac biomarkers with a rising/falling trend, plus at least one of:
symptoms of ischemia, ECG changes, new pathological Q waves, or imaging
evidence of new loss of viable myocardium or regional wall motion abnormality.
*Treatment: Acute and Long-Term Management -
Treatment of MI is time-critical, aiming to restore blood
flow and prevent further damage:
- **Immediate Actions**:
- Administer aspirin
(if not allergic) to prevent further clotting.
- Use nitroglycerin
for chest pain relief, and consider opioids for severe pain, though they do not
improve mortality outcomes.
- Supplemental oxygen
for those with low oxygen levels or shortness of breath.
- **Emergency Interventions**:
- **For
STEMI**: Percutaneous coronary intervention (PCI) within 90–120
minutes, or thrombolysis (e.g., tissue plasminogen activator, reteplase,
streptokinase, tenecteplase) within 30 minutes if PCI is delayed.
- **For
NSTEMI**: Manage with heparin, and PCI within 1–3 days for high-risk
patients, using P2Y12 inhibitors (e.g., clopidogrel, prasugrel, ticagrelor),
heparins, and glycoprotein IIb/IIIa inhibitors as needed.
- **Post-MI Management**:
- Aspirin
indefinitely, dual antiplatelet therapy (aspirin + P2Y12 inhibitor) for up to
12 months.
- Beta-blockers
within 24 hours, ACE inhibitors within 24 hours and continued indefinitely,
statins for cholesterol management, and aldosterone antagonists for left
ventricular dysfunction.
- Rescue PCI for
cardiogenic shock or poor response to thrombolysis.
- Cardiac
rehabilitation and influenza vaccine (15–45% benefit) to reduce recurrence
risk.
*Prevention: Primary and Secondary Strategies -
Preventing MI involves both primary prevention (reducing
initial risk) and secondary prevention (preventing recurrence):
- **Primary Prevention**:
-
**Lifestyle Changes**: Engage in 150 minutes of moderate or 75 minutes of
vigorous aerobic exercise weekly, maintain a healthy weight, quit smoking,
limit alcohol, and follow a Mediterranean diet low in saturated fats, trans
fats, and salt.
- **Dietary
Interventions**: Substitute unsaturated fats, and support public health
measures like food labeling and reducing salt/saturated/trans fats in processed
foods.
-
**Medications**: Statins for elevated risk, with aspirin use debated due to
bleeding risk (consult healthcare provider).
- **Secondary Prevention**:
- Lifestyle
modifications: Stop smoking, gradual exercise after 1–2 weeks, healthy diet low
in saturated fat and cholesterol.
- Medications as
outlined in long-term management.
- Participate in
cardiac rehabilitation programs.
- Annual influenza
vaccination, shown to reduce MI risk by 15–45%.
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