Young AMI

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Young AMI

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Introduction

• Myocardial infarction in persons under the age of
  45 years accounts for 6 to 10 of all myocardial
  infarctions in the United States.
• In this age group, it is predominantly a disease
  of men.
• Unlike older patients, approximately half of
  young patients have single-vessel coronary
  disease, and in up to 20, the cause is not
  related to atherosclerosis.

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Coronary Anatomy

• Most young patients with MI, up to 82 in one
  study, have typical atherosclerotic coronary
  artery disease. This manifests more often as
  single-vessel disease in younger patients than in
  older patients.
• However, approximately 20 of young patients with
  MI do not have atherosclerosis, such as cocaine
  use or anomalous coronary arteries.
• Multivessel coronary disease appears to be
  related to the number of risk factors, especially
  for DM patients.

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Etiology
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Risk Factors
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Atherosclerosis
Figure 233-5 The atherosclerotic process. A.
Artery depicting early fatty streak development.
B. 1, LDL becomes oxidized within the arterial
subendothelial space. 2, Circulating monocytes
are recruited to the subendothelial space by
chemoattractants including oxidized LDL. 3, These
monocytes undergo differentiation, becoming
macrophages, which are scavenger cells that
recognize and accumulate oxidized LDL. 4, The
lipid-laden macrophages then become foam cells,
which cluster under the endothelial lining to
form a bulge into the artery. 5, This bulge is
called a fatty streak and is the first overt sign
of atherosclerotic change. C. Cross-section of an
artery with an atherosclerotic lesion with a
narrowed lumen.
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Cigarette Smoking

• Smoking produces endothelial dysfunction and can
  precipitate coronary spasm.
• Cigarette smoking appears to be the most common
  risk factor in young MI patients.
• The extent of smoking appears to be inversely
  related to the age at which the first MI occurs.

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Lipid Abnormalities
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Lipid Abnormalities

• Homozygous familial hypercholesterolemia appears
  to have the most consistent relation with
  premature atherosclerosis and MI.
• Increased TG levels and decreased HDL cholesterol
  levels have also been reported in MI patients
  under age 45 years.

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Lipid Abnormalities
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Family History

• A positive family history of coronary artery
  disease is a major risk factor for MI in young
  patients.
• In an autopsy study of 136 infants under 1 year
  old, mean luminal narrowing in the left coronary
  artery was 1.4 times greater in infants with no
  family history.
• Increase of the risk in young patients with
  family history may be due to inherited disorders
  of lipid metabolism, blood coagulation, or other
  genetic factors.

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Obesity

• Obesity, particularly the male pattern of
  centripetal or visceral fat accumulation, can
  promote an atherogenic dyslipidemia characterized
  by elevated TG, a low HDL level, and glucose
  intolerance.
• Approximately 30 to 58 of young patients with
  coronary artery disease are obese, a
  significantly greater proportion than in older
  patients.

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Hypertension

• Hypertension is less common in young MI patients
  than in older patients.
• In addition, hypertension is common in patients
  with left main coronary artery stenosis who are
  under age 45 years.

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DM

• A major feature of elevated cardiovascular risk
  in patients with type 2 diabetes probably relates
  to the abnormal lipoprotein profile associated
  with insulin resistance known as diabetic
  dyslipidemia.
• The LDL particles tend to be smaller and denser
  and thus more atherogenic.
• DM is also less likely to be associated with MI
  in young patients than in older patients.
• Less than 10 of young patients have DM.

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Summary
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Non-atherosclerosis

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Cocaine

• Cocaine blocks the presynaptic reuptake of
  norepinephrine and dopamine, producing an excess
  of these neurotransmitters at the site of the
  postsynaptic receptor.
• Acutely, cocaine increases heart rate and blood
  pressure and decreases coronary blood flow
  through vasospasm, thereby leading to increased
  myocardial oxygen demand and reduced oxygen
  supply.

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Cocaine

• All young patients presenting with symptoms
  suggestive of myocardial ischemia should be
  questioned about cocaine use.

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Hypercoagulable States
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Hypercoagulable States

• High levels of factor VII activity or fibrinogen
  were associated with substantially increased risk
  of coronary events among men 40 to 64 years old.
• Use of oral contraceptives, which produce a
  prothrombotic state, has been an important risk
  factor for MI in young women.

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Hypercoagulable States

• Decreased fibrinolytic activity as a result of
  increased levels of plasminogen activator
  inhibitor-1(PAI-1) has been reported in MI
  patients under age 45 years.
• Deficiencies of the natural anticoagulant
  proteins, such as protein C, protein S, and
  antithrombin III are usually associated with
  venous thromboembolism.

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Hypercoagulable States

• Elevated plasma homocysteine levels are
  associated with coronary artery disease,
  presumably as a result of the effects of
  homocysteine on endothelial and vascular smooth
  muscle proliferation.
• Acquired or inherited platelet disorders have
  been associated with MI in young patients.

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Coronary Anomalies

• Congenital coronary artery anomalies account for
  approximately 4 of MIs in young patients.
• Several such anomalies, including a deep
  intramyocardial course, an origin from the wrong
  coronary sinus, or ostial obstruction, have been
  associated with MI and sudden death in young
  patients.

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Others

• Spontaneous coronary artery dissection
• Coronary arteritis in vasculitic disorders such
  as SLE
• Coronary aneurysms in Kawasakis disease
• Blunt chest trauma causing coronary thrombosis or
  dissection
• Mediastinal irradiation therapy for Hodgkins
  disease
• Valvular abnormalities
• Embolization from infective endocarditis

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Prognosis

• Young patients with MI have a more favorable
  prognosis than older patients.
• The incidence of cardiogenic shock, stroke, and
  left ventricular dysfunction is lower in young
  patients, probably accounting for their better
  outcome.

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Thank you for your attention