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The second most common form of heart
muscle disease is hypertrophic cardiomyopathy. Physicians sometimes
call it by other names: idiopathic hypertrophic subaortic stenosis (IHSS),
asymmetrical septal hypertrophy (ASH), or hypertrophic obstructive
cardiomyopathy (HOCM).
In hypertrophic cardiomyopathy, the
growth and arrangement of muscle fibers are abnormal, leading to
thickened heart walls. The greatest thickening tends to occur in the
left ventricle (the heart's main pumping chamber), especially in the
septum, the wall that separates the left and right ventricles. The
thickening reduces the size of the pumping chamber and obstructs blood
flow. It also prevents the heart from properly relaxing between beats
and so filling with blood. Eventually, this limits the pumping action.
Hypertrophic cardiomyopathy is a rare
disease, occurring in no more than 0.2 percent of the U.S. population.
It can affect men and women of all ages. Symptoms can appear in
childhood or adulthood.
Causes
Most cases of hypertrophic
cardiomyopathy are inherited. Because of this, a patient's family
members often are checked for signs of the disease, although the signs
may be much less evident or even absent in them. In other cases, there
is no clear cause.
Symptoms
Many patients have no symptoms. For
those who do, the most common are breathlessness and chest discomfort.
Other signs are fainting during physical activity, strong rapid
heartbeats that feel like a pounding in the chest, and fatigue,
especially with physical exertion.
In some cases, the first and only
manifestation of hypertrophic cardiomyopathy is sudden death, caused
by a chaotic heartbeat. The heart's lower chambers beat so chaotically
and fast that no blood is pumped. Instead of beating, the heart
quivers.
In advanced stages of the disease,
patients may have severe heart failure
and its associated symptoms, including fluid accumulation or
congestion.
Diagnosis
By listening through a stethoscope,
a physician may hear the abnormal heart sounds characteristic of
hypertrophic cardiomyopathy. An electrocardiogram (EKG,
or ECG) may help diagnose the condition by detecting changes in the
electrical activity of the heart as it beats.
Echocardiography is one of the
best tools for diagnosing hypertrophic cardiomyopathy. It uses
sound waves to detect the extent of muscle-wall thickening and to
assess the status of the heart's functioning.
Physicians also may request
radionuclide studies to gather added information about the
disease's effect on how the heart is pumping blood.
Other tests that also may provide
useful information are the chest x ray, cardiac catherization, and
a heart muscle biopsy.
Treatment
Treatments for hypertrophic
cardiomyopathy vary but can include the following:
- Lifestyle changes. Patients
with serious electrical and blood-flow abnormalities must be less
physically active.
- Medications. Various
drugs are used to treat the disease. They include beta blockers (to
ease symptoms by slowing the heart's pumping action), calcium
channel blockers (to relax the heart and reduce the blood pressure
in it), antiarrhythmic medications, and diuretics (to ease heart
failure symptoms).
However, drugs do not work in all
cases or may cause adverse side effects, such as fluid in the lungs,
very low blood pressure, and sudden death. Then, other treatment,
such as a pacemaker or surgery, may be needed.
- Pacemakers. These change the
pattern and decrease the force of the heart's contractions. The
pacemaker can reduce the degree of obstruction and so relieve
symptoms. A pacemaker needs to be carefully monitored after its
insertion in order to properly adjust the electrical impulse. Some
patients who have a pacemaker inserted feel no relief and go on to
have heart surgery.
- Surgery. This usually calls
for removal of part of the thickened septum (the muscle wall
separating the chambers) that is blocking the blood flow. Sometimes,
surgery also must replace a heart valve - the mitral valve, which
connects the left ventricle and the left atrium, the upper chamber
that receives oxygen-rich blood from the lungs.
Surgery to remove the thickening
eases symptoms in about 70 percent of patients but results in death
in about 1 to 3 percent of patients. Also, about 5 percent of those
who have surgery develop a slow heartbeat, which is then corrected
with a pacemaker.
Course of the disease
The course of the disease varies. Many
patients remain stable; some improve; some worsen in symptoms and lead
severely restricted lives. Patients may need drug treatment and
careful medical supervision for the rest of their lives.
Hypertrophic cardiomyopathy patients
also are at risk of sudden death. About 2 to 3 percent die each year
because the heart suddenly stops beating. This cardiac arrest is
brought on by an abnormal heartbeat. Over 10 years, the risk of sudden
death can be 20 percent or more.
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