Acute Myocardial Infarction

What is acute myocardial infarction?

Acute myocardial infarction, also known as heart attack, is
myocardial necrosis caused by an immediate occlusion of a
coronary artery. The occlusion happens when the blood supply
to the heart is blocked. The most common cause of the
blockage is the accumulation of fat, cholesterol, and other
chemical substances in the arteries that supply the heart,
forming a plaque.

Types of AMI

Myocardial infarction can be classified, based on etiology and
circumstances, into five types:
Type one: Spontaneous myocardial infarction due to ischemia
because of a primary coronary event, such as plaque, rupture,
erosion, fissuring, or coronary artery dissection.
Type 2: increased oxygen demand or decreased blood supply
causing ischemia.
Type 3: Because of unexpected cardiac death.
Type 4a: Related to percutaneous coronary intervention.
Type 4b: Linked to documented stent thrombosis.
Type 5: Linked to coronary artery bypass grafting.

Symptoms

While chest discomfort and shortness of breath are the most
common symptoms of a heart attack, the symptoms can be
extremely variable. The most frequent signs and symptoms of a
heart attack are as follows:
● Pressure, tightness, discomfort, or a squeezing or hurting
feeling in the chest that may move to your neck, jaw, or
back.
● Nausea, indigestion, heartburn, or abdominal discomfort.
● Shortness of breath
● Sweats
● Fatigue
● Sudden dizziness or lightheadedness

Causes of acute myocardial infarction

The main cause of the AMI or heart attack is the accumulation
of plaques in the coronary arteries, resulting in atherosclerosis,
which leads to artery blockage.
This plaque can rupture and spill its substances into the
bloodstream. This can form a clot, which can block the blood
flow to the heart causing ischemia.
The blockage may be partial or complete; a partial blockage is
when the patient has an ST elevation myocardial infarction
(STEMI). Meanwhile, a complete blockage is when the patient
doesn’t have an ST elevation myocardial infarction (NSTEMI).
Also, a spasm of a coronary artery can cause a heart attack as
it cuts off blood supply to a portion of the heart muscle. Using
tobacco, cocaine and some other illicit drugs can result in heart
attacks too.
Some studies have shown that COVID-19 infection can
potentially harm the heart and cause a heart attack

Risk factors

The main cause of the AMI or heart attack is the accumulation
of plaques in the coronary arteries, resulting in atherosclerosis,
which leads to artery blockage.
This plaque can rupture and spill its substances into the
bloodstream. This can form a clot, which can block the blood
flow to the heart causing ischemia.
Some factors can increase the risk of myocardial infarction
because of the accumulation of fatty deposits (atherosclerosis),
including:
● Age, men older than 45 and women older than 55 are at
higher risk of heart attacks.
● Hypertension increases the risk of artery damage.
● Diabetes, increasing blood glucose levels is associated
with heart attacks.
● Hypercholesterolemia narrows the arteries.
● Obesity is strongly related to hypercholesterolemia and
hypertension.
● Tobacco, smoking for a long time, or secondhand
smoking.
● Illicit drugs, cocaine, and amphetamines trigger coronary
artery spasms.
● Metabolic syndrome means patients are twice as likely to
develop heart diseases.
● Family History is a significant risk factor for heart attacks.
● Less physical activity increases blood cholesterol levels
which is more likely to cause atherosclerosis.
● Stress
● Preeclampsia, a history of elevated blood pressure during
pregnancy is a risk factor.
● Autoimmune diseases, some conditions increase the risk
of heart attacks, including RA and SLE

Diagnosis of AMI

After knowing the case history, vital signs, and symptoms; the
patient should be connected to a heart monitor and get
checked by some tests; including:
● ECG. to check cardiac electricity.
● Blood tests. To check for certain heart proteins.
The patient may have to undergo some other tests; including:
● Chest x-ray; to check the heart and blood vessels’ size
and fluid in the lungs.
● Echocardiogram; to identify the damaged area in the heart
by checking the heart’s chambers and valves.
● Coronary catheterization (angiogram); to reveal the area
of blockage.
● Cardiac CT or MRI; to know the extent of damage from the
attacks and diagnose other heart problems.

Prognosis

AMI is associated to high mortality rate. The prognosis depends
mainly on the muscle damage extent.
Patients who get early perfusion (thrombolytic treatment within
30 minutes of arrival or PCI within 90 minutes) get better
results. Furthermore, the prognosis gets better if the ejection
fraction is preserved and the patient started aspirin,
beta-blockers, and ACE inhibitors.
There are some factors can have negative effect on AMI
prognosis; including diabetes, old age, delayed reperfusion,
CHF, diminished EF, elevated CRP and BNP, prior MI, PVD, or
Stroke

Acute Myocardial Infarction treatment

Treatment of AMI can be classified into three procedures:

Medications

➢Aspirin reduces blood clotting and maintains the blood
flow through the heart.
➢Thrombolytics, dissolve the blood clots.
➢Antiplatelet Agents prevent forming other blood clots.
➢Other blood-thinning medications, such as heparin
decreases blood stickiness and the possibility to form
blood clots.
➢Pain relievers, to decrease the pain.
➢Nitroglycerin treats angina by widening the blood vessels.
➢Beta-blockers relax the heart muscles, decrease blood
pressure, and control the heart rhythm.
➢ACE inhibitors control blood pressure.
➢Statins to control blood cholesterol.

Surgical procedures

➢Coronary angioplasty and stenting (PCI), by inserting a
catheter through an artery to the blocked artery in the
heart. This procedure is recommended to be done
immediately during a heart attack.
➢Coronary artery bypass surgery, by sewing blood vessels
beyond the blocked artery, allows blood flow to the heart.
This procedure can be done during the heart attack and
might be done about three to seven days after the attack.

Cardiac rehabilitation

Cardiac rehab programs are offered by some hospitals
including four main aspects: medication, lifestyle changes,
emotional issues, and returning to normal activities.
This program could be two weeks to a couple of months.
Patients who follow cardiac rehab programs are more
likely to get better and live longer.

References

PubMed
MayoClinic
NCBI

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