What is an MI?
Myocardial infarction is the medical term for a heart attack. It has
also been known as coronary thrombosis or simply as a "coronary".
The pain of myocardial infarction lasts longer than that of angina pectoris.
Generally there is a prolonged, sudden-crushing chest pain accompanied
by shortness of breath, sweating, nausea, vomiting and perhaps lightheadedness.
This pain may spread to the arms, neck, jaw, shoulders and back.
For some people symptoms of angina and heart attack may be felt only as
shortness of breath. For others, heart attacks may occur silently without
any symptoms of chest pain or they may be passed off as mild indigestion.
The heart attack process:
All tissue in the body requires a constant blood supply bringing oxygen
and nutrients. The heart is no exception. The coronary arteries are the
blood vessels that bring blood to the heart. When one of these arteries
becomes severely narrowed or blocked, the blood supply to a part of the
heart's muscle is reduced. When this lack of blood supply lasts longer
than 20 to 30 minutes, heart muscle damage may occur. This process is
known as a heart attack. Other names used to refer to a heart attack are
Myocardial Infarction, or simply a MI.
Myocardial infarction is not a sudden event; it is a process, which evolves
over time. This process begins with the initial damage and ends with a
healed, well-formed scar that replaces the area of damage. In the first
hours of a heart attack the patient may experience chest pain and all
the other symptoms of Angina or other symptoms described earlier. There
may also be dangerous arrhythmias and sudden death. This is why it is
necessary to go the hospital as quickly as possible.
The pain of a heart attack may last from six to 12 hours and sometimes
longer. During this period you are usually treated with pain relievers
such as morphine. Patients who arrive early enough may receive blood clot
dissolving medications to try and reopen the blocked artery. That is why
it is important to present to hospital promptly when possible heart attack
symptoms occur. The sooner these blood clot dissolving medications are
administered the better and the more heart muscle can be saved. These
blood clot dissolving medications include Streptokinase, t-PA (which stands
for tissue plasminogen activator) and r-PA. These agents are intended
to be given as soon as possible after the start of a MI and act to dissolve
blood clot at the site of cholesterol plaque rupture. By opening the coronary
arteries, these agents limit the size of the heart attack and save heart
muscle. When it comes to a heart attack, remember that time is muscle.
The sooner you get to hospital, the better.
Other medications such as aspirin and heparin to thin the blood and
beta blockers and angiotensin converting enzymes (ACE) inhibitors may
be given to reduce the size of the heart attack and preserve pump function.
(See section on cardiac medications for more information).
For the first two to four days you will be monitored in the Intensive
Care Unit. This is primarily to detect complications such as arrhythmia.
After this you will be transferred to a regular ward for further monitoring
and your level of physical activity will be gradually increased to normal
over the next week.
A person with a small, uncomplicated heart attack may expect to go home
after four to seven days. People with larger heart attacks or with complications
may stay in hospital longer. In general, a stress test is done prior to
discharge to assess your risk for another heart attack. If you develop
a recurrence of your presenting symptom, usually chest pain, then an angiogram
may be indicated (see the section on cardiac testing). At home you will
gradually increase your activity level to normal over the next two to
four weeks. Someone with a sedentary or office job may return to work
after approximately two months. Someone doing physical labor is often
advised to remain off work for three months.
Remember that recovering from a heart attack takes time. The healing
process begins immediately and may take six to eight weeks to complete.
The area of heart muscle damage is permanent but unless that area is large,
the remainder of the muscle is usually adequate to permit you to lead
a normal life. A firm scar replaces the heart muscle that is damaged and
the remaining heart muscle takes over the work of the damaged area.
Usually after a heart attack you will be given a variety of medications
intended to reduce your risk of another heart attack and to help the heart
heal. It may seem that you are being given a lot of pills, but most of
these prescriptions are based on strong medical evidence. Other medications
are given to control symptoms such as congestion or angina. See the section
on cardiac medications for a more detailed description of the pills you
have been prescribed. These may include:
2. Beta (ß)-blockers
3. ACE inhibitors
4. Cholesterol lowering agents- usually a "statin"
5. Nitroglycerin and long acting nitrates
6. Calcium channel blockers
COMPLICATIONS OF MYOCARDIAL INFARCTION
One of the most important reasons to be in hospital during a heart attack
is to watch for complications. The key complication to watch for is recurrence
of chest pain or angina. Angina recurring after a heart attack is considered
UNSTABLE ANGINA. This may indicate that there is some heart muscle that
is still at risk of damage from narrowed or blocked coronary arteries
and may require further investigations such as an angiogram or cardiac
catheterization (see section on cardiac investigations and procedures).
Often after a heart attack the outer lining of the heart or pericardium
becomes inflamed, a condition known as PERICARDITIS. This may produce
sharp chest pains that may also be felt in the shoulders, neck and arms.
Such pains may worry you but they are part of the healing process and
are not dangerous. Other complications such as arrhythmias and congestive
heart failure have already been described.