Myocardial infarction of young patients.ppt

Young AMI

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Am J MEd. 1999;107;254-261 Myocardial Infarction in Young Patients

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.


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.


Etiology


Risk FactorsAtherosclerosis Non-atherosclerosis

Cocaine use

Hypercoagulable states

Coronary artery anomalies

others

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.


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.


Lipid Abnormalities


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.


Lipid Abnormalities


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.


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.


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.


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.


Summary

Young Old

Smoking ++++ ++

Lipid Abnormalities

+++ ++

Family History +++ +

Obesity +++ +

Hypertension + +++

DM + +++

Non-atherosclerosis

20%


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.




Cocaine

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

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.



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.



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.


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.


Others

Spontaneous coronary artery dissection

Coronary arteritis in vasculitic disorders such as SLE

Coronary aneurysms in Kawasaki’s disease

Blunt chest trauma causing coronary thrombosis or dissection

Mediastinal irradiation therapy for Hodgkin’s disease

Valvular abnormalities

Embolization from infective endocarditis


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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Myocardial infarction of young patients.ppt