(also known as a Heart Attack)
Acute myocardial infarction (AMI) is commonly
called a heart attack. It is caused by the rapid
development of myocardial necrosis (tissue death
of a portion of the heart muscle) resulting from
a critical imbalance between the oxygen supply
and demand of the myocardium. This usually results
from plaque rupture with thrombus formation in a
coronary vessel, resulting in an acute reduction
of blood supply to a portion of the myocardium.
Facts & Figures
This year in the United States:
- AMI will be a leading cause of morbidity and
- Approximately 500,000-700,000 deaths will
result from ischemic heart disease.
- More than one half of these deaths will
occur in the prehospital setting
- In-hospital fatalities will account for
approximately 10 percent of all deaths.
- Approximately 10 percent of the additional
deaths will occur in the first year postinfarct.
What Causes a Myocardial Infarction:
The most common cause of AMI is narrowing of the
epicardial blood vessels due to atheromatous plaques.
Plaque rupture with subsequent exposure of the
basement membrane results in platelet aggregation,
thrombus formation, fibrin accumulation, hemorrhage
into the plaque, and varying degrees of vasospasm.
This can result in partial or complete occlusion of
the vessel and subsequent myocardial ischemia. Total
occlusion of the vessel for more than 4-6 hours
results in irreversible myocardial necrosis, but
reperfusion within this period can salvage the
myocardium and reduce morbidity and mortality.
Other causes of AMI include hypoxia, emboli to coronary
arteries, arteritis, coronary anomalies, and the use
of cocaine, amphetamines, and ephedrine.
Signs and Symptoms of Myocardial Infarction:
There are various signs and symptoms that may
indicate a patient may be suffering from myocardial
infarction. These signs and symptoms include:
There are also several risk factors for the formation
of atherosclerotic plaque (which can rupture with
resulting myocardial infarction) including age, sex,
smoking, hypercholesterolemia and hypertriglyceridemia,
diabetes mellitus, poorly controlled hypertension,
family history, and a sedentary lifestyle.
- Chest pain, usually across the anterior
precordium, is described as tightness,
pressure, or squeezing
- Pain may radiate to the jaw, neck, arms,
back, and epigastrium. The left arm is
affected more frequently than the right arm.
- Dyspnea, which may accompany chest pain
or occur as an isolated complaint, indicates
poor ventricular compliance in the setting
of acute ischemia.
- Nausea and/or abdominal pain often are
present in infarcts involving the inferior
- Lightheadedness and syncope
- Nausea and vomiting
- Elderly patients and those with diabetes may
have particularly subtle presentations and may
complain of fatigue, syncope, or weakness.
Diagnosing a Myocardial Infarction:
Upon physical examination:
Immediate diagnosis is crucial. Any delay in diagosis
or treatment can result in the death of the patient.
- Patients with ongoing symptoms might be noted
to lie quietly in bed and appear pale and
- Hypertension may precipitate AMI, or it may
reflect elevated catecholamines due to anxiety,
pain, or exogenous sympathomimetics
- Hypotension indicates ventricular dysfunction
due to ischemia. It usually indicates a large
infarct and may be observed with a right
- Acute valvular dysfunction may be present
- Congestive heart failure (CHF) may occur with
neck vein distention, third heart sound (S3),
rales on pulmonary examination
- New or worsening mitral regurgitant murmur
may be noted
- A fourth heart sound is a common finding in
patients with poor ventricular compliance that
is due to a preexisting heart disease or
- Dysrhythmias may be present
- With heart block or right ventricular failure,
cannon jugular venous a waves may be noted
When a patient presents with symptoms that could be the
result of a myocardial infarction, a physician should
immediately order a number of diagnostic procedures to
rule out AMI. Any delay in the diagnosis of AMI could
result in the death of the patient. Appropriate diagnostic
procedures include laboratory studies such as:
In addition to laboratory studies, the physician may also
order imaging studies that can help identify the presence
of abnormalities or complications resulting from AMI.
Possible imaging studies include:
- Creatine kinase - MB (CK-MB)
- Troponin I
- Complete blood count
for evidence of leukocytosis, anemia, elevated
erythrocyte sedimentation rate (ESR) levels,
and elevated serum lactase dehydrogenase (LDH)
In addition to the laboratory tests and imaging studies
mentioned above, a physician whose patient exhibits
symptoms consistent with AMI should immediately order an
- Chest x-ray
A Chest X-ray may provide clues to an alternative
or complicating diagnosis (eg, aortic dissection,
pneumothorax). The X-ray also reveals complications
of AMI, particularly pulmonary edema, and CHF.
Use 2-dimensional and M-mode echocardiography when
evaluating wall motion abnormalities and overall
ventricular function. This also can identify
complications of AMI (eg, valvular insufficiency,
ventricular dysfunction, pericardial effusion).
- Technetium-99m sestamibi scan
Technetium-99m is a radioisotope that is taken up
by the myocardium in proportion to the blood flow
and is redistributed minimally after injection.
This allows for time delay between injection and
imaging. It has potential use in identifying
infarct in patients with atypical presentations
or uninterpretable ECGs. Normal scan findings are
associated with an extremely low risk of subsequent
- Thallium scanning
Thallium accumulates in the viable myocardium.
- Electrocardiogram - Approximately one half of patients
have diagnostic changes on their initial ECG.
It should also be kept in mind that patients experiencing
AMI may have complications such as tachyarrhythmia,
bradyarrhythmia, cardiogenic shock, and valvular insufficiency.
Treatment for a Myocardial Infarction
Once a patient has been diagnosed as suffering from AMI,
the patient should receive immediate treatment. Treatment
Generally, emergency physicians and cardiologists work
together to determine the most appropriate course of
treatment for the patient.
The main goals of treatment are rapid identification
of candidates for thrombolysis, coronary reperfusion
via thrombolytic therapy, or percutaneous transluminal
angioplasty and preservation of coronary artery patency
analgesics, and the myocardium.
- All AMI patients should be placed on telemetry
- Two large-bore IVs should be inserted
- Pulse oximetry should be performed, and
appropriate supplemental oxygen should be
given (maintain oxygen saturation >90 percent)
- The Chest X-Ray should be carefully reviewed
to identify possible contraindications to
thrombolysis (e.g., aortic dissection)
- The emergency physician should decide whether
to administer a thrombolytic agent
- Pharmacologic intervention is likely to include
the immediate administration of aspirin and
beta-blockade for rate control and decrease
of myocardial oxygen demand if not contraindicated
- Additional intervention may include morphine
sulphate, anxiolytic, heparin, platelet aggregation
(IIb/IIIa receptor) inhibitor, ACE inhibitor
- Antiarrhythmic agent
- Angiography may be performed prior to procedures
to re-establish coronary perfusion.
- Percutaneous transluminal coronary angioplasty
(generally used selectively for patients failing
to respond to thrombolytics)
- Intra-aortic balloon counter pulsation
- Coronary artery bypass graft (CABG)
Once a patient has been stabilized, additional treatment
may consist of prescription of beta-blockers, nitrates,
heparin, lidocaine, angiotensin-converting enzyme (ACE)
inhibitors, salicylates, thrombolytics, nitroglycerin,
and calcium channel blockers, as indicated.
Prognosis for Patients with Myocardial Infarction
Although the prognosis for patients with myocardial
infarction depends on a number of factors, the timing
and nature of intervention, the success of the
intervention (ie, infarct size), and the post-MI
management are critical. A delay in diagnosis and
treatment, as well as any inappropriate or
counterindicated treatment, can result in the death
of the patient.
If someone you love has died because a doctor or other
health care professional failed to diagnose a Myocardial
Infarction (or heart attack) and failed to provide
appropriate treatment, you should immediately
contact a competent attorney. The attorney will work
with you to determine whteher there may a medical
malpractice claim resulting from the failure to
diagnose or provide appropriate treatment.
Call or email for a Free Attorney Consultation
Law Office of Joseph A. Hernandez, P.C.
Phone: (781) 461-9400
Toll Free: (866) 461-9400
Please be sure to include your name and a telephone number where we can reach you.
Thank you for visiting the Law Office of Joseph A.
Hernandez. The material located on our law firm's
web site is intended to be a resource for present
and prospective clients for informational purposes
only and is not intended to be legal advice. This
web site is not an offer to represent you. The act
of sending electronic mail to our firm or to
Attorney Hernandez does not create an attorney-client
relationship and does not obligate the Law Office of
Joseph A. Hernandez or Mr. Hernandez to respond to
your email or to represent you. No attorney-client
relationship will be formed unless you enter into a
signed agreement of representation with the Law
Office of Joseph A. Hernandez. You should not act,
or refrain from acting, based upon any information
at this web site without seeking professional legal
counsel. Under the rules of the Supreme Judicial
Court of Massachusetts and other rules, this
material may be considered advertising. The listing
of areas of practice does not represent official
certification of expertise therein.